ASTR 101 - Midterm II
What does a downward transition to a lower energy level entail?
- downward transitions to lower energy levels result in emission of photons, producing a unique pattern of emission lines corresponding to energy level differences -- makes sense because if you are at an energy level of 6 and want to transition down to an energy level of 3, you have to emit / lose three photons - because those atoms can absorb photons with some energies and in the same way that they can demit them, upward transitions produce a pattern of absorption lines at the same wavelengths -- makes sense, if I am at an energy level of 3 and want to transition up to an energy level of 6, I need to absorb three photons
Describe the relationship between tidal heating and Io
- due to its elliptical orbit, Io is squashed and stretched as it orbits Jupiter -- it is squashed down at the 6 and 12 o'clock positions in its orbit (assuming 12 o'clock is on the right of Jupiter) and then it is stretched up at the 3 and 9 o'clock positions in its orbit
what is the composition of Earth's atmosphere?
- earth's atmosphere is mostly molecular nitrogen and molecular oxygen with a little carbon dioxide and water - there is a modest greenhouse effect -- this modest greenhouse effect is not overbearing (like Venus) and not under bearing so that it is able to raise the average temperature above freezing, allowing liquid water to form on the surface (just hot enough to cause water vapor and water -- hydrogen compound -- to condensate), but not too hot that all of the water then vaporizes into the atmosphere, like it does on Venus
What is a Super-Earth?
- exoplanet that is more massive than our Earth
what exactly is Jupiter's Great Red Spot?
- it is a storm that is twice as wide as Earth - it has existed for at least three centuries - has very high pressures in the center of the eye
What is the Astrometric Method?
- one of three methods of indirect exoplanet detection by which we can measure the change in position of a star due to the gravitational tug (i.e. its pull -- Newton's 3rd Law = action - reaction) of the orbiting planet
what must gravity be able to do in order to form a star?
- overcome thermal pressure
what limits the Doppler Method?
- Distance -- planets at greater distances are harder to detect with the Doppler Method, only bright, nearby stars can be detected using the Doppler Method
What are the largest of the Kuiper planetesimals called?
- Dwarf Planets
What is an Emission Line Spectrum? How is it characterized? What is one example?
- Emission Line Spectrum show the emittance, or sending of certain wavelengths or elements - Emission Line spectrum are characterized by high peaks in a graph where things are sent Example - a thin or low-density cloud of gas emits light only at specific wavelengths that depend on its composition and temperature, producing a spectrum with bright emission lines
What is Enceladus and what is unique about it?
- Enceladus is a medium moon of Saturn - it has ice volcanoes that suggest it might have a subsurface ocean
Why isn't Pluto considered a normal planet?
- MUCH smaller than the terrestrial or Jovian planets - Icy composition like a comet - elliptical, inclined orbit - More in common with a comet than with the eight major planets - Part of the Kuiper Belt, which also indicates objects similar to Pluto in size
Why are medium and large jovian moons different from small jovian moons?
- Medium and large jovian moons have enough self-gravity to be spherical - they have substantial amounts of ice - they formed in orbit around Jovian planets - They have circular orbits that go in the same direction as planet rotation out of Jovian nebulas (analogous to planets forming out solar nebula)
When is the only time that photons are emitted or absorbed?
- Photons are only emitted or absorbed when electrons transition between energy levels
In general, where do stars come from?
- Stars form in huge, dark, dusty clouds of molecular gas with cold temperatures of around 10 - 30 K
What does it mean when we say, "stars have different spectral types"?
- Stars have different spectral types, meaning that the strengths of absorption lines vary depending on type
Why is the Gale Crater important? Where is it?
- The gale Crater is where the Curiosity Rover from Earth landed - The Gale crater is on mars
what happens on the electromagnetic spectrum as the temperature of an object increases?
- The hotter an object, the more light it emits at ALL wavelengths - the hotter an object, the more its peak brightness shifts to shorter wavelengths As the temperature of an object increases: 1. the brighter it gets at all wavelengths 2. the peak brightness shifts to shorter wavelengths
what is the color and surface temperatures of the hottest stars?
- The hottest stars are blue and have a surface temperature of around 50,000 K (the Sun has a surface temperature of about 6,000 K)
What happens in the Radiation Zone of the Sun?
- The radiation zone is where energy is carried from the core by radiation - this is where energy from the core is transported outward by photons, but takes a very long time
How big is the size of the Sun's orbit around the center of mass of the solar system?
- The size of the Sun's orbit around its center of mass is not much bigger than the size of the Sun itself
What is Triton's surface like?
- Triton's surface shows a cantaloupe terrain - frost deposits - wind streaks - lava-filled impact basins similar to the lunar maria (on the Moon), but the lava was water or slush rather than molten rock -- makes sense since Neptune is the furthest out in the solar system and thus it would be extremely cold
Why are Uranus and Neptune, although smaller in size compared to Saturn, denser than Saturn?
- Uranus and Neptune, although smaller in size compared to Saturn, are denser than Saturn because they have less H and He
Why is Venus' CO2 all in its atmosphere and not in its rocks, like it is on Earth?
- Venus lacks oceans to dissolve the carbon dioxide and lock it away in rocks on the seafloor, like earth is able to do - On earth, the rain washed CO2 into the oceans, where it gets incorporated into rocks. This is only the case for earth
what does "a" stand for in Newton's form of Kepler's 3rd law for calculating the period and mass of a binary system?
- a = average SEPARATION between the two stars
What kind of light does a brown dwarf emit?
- a brown dwarf emits infrared light because of heat leftover from contraction
how does a glass prism interact with light?
- a glass prism reflects and scatters light
what does a short wavelength mean?
- a short wavelength corresponds to high frequency radiation (dangerous)
what are the luminosities of the least luminous stars?
- the least luminous stars have luminosities that are equal to about 10,000 times less than that of the Sun's (10^-4)
What is the cause of the sunspot cycle?
- the sunspot cycle has something to do with the winding and twisting of the Sun's magnetic field
briefly, what is visible light?
- visible light is just a tiny section on the much broader spectrum of light
what are the two ways in which a planet can lose its atmosphere?
1. Solar winds 2. Close distance to the Sun
What is the formula for Luminosity, determined only after we measure both its distance and its Apparent Brightness?
Luminosity: 4(pi)(distance)^2 x Apparent Brightness
Generally, what is the difference between thermal pressure and degeneracy pressure?
Thermal pressure - depends on heat content and temperature - is the main form of pressure in most stars Degeneracy Pressure - particles cannot be in the same state in the same place - does not depend on heat content and temperature
What are Brown Dwarfs?
- brown dwarfs are the result of what happens when degeneracy pressure halts the contraction of protostars with masses that are .08 times the mass of the sun - I.e. Brown Dwarfs are when a Protostar fails to meet the temperature threshold for fusion and degeneracy pressure is forced to stave off the compression of gravity -- the Protostar was not massive enough to get hot enough to start fusion and thus degeneracy came into play and it is not not a main-sequence star, but rather a brown dwarf
what are comets?
- comets formed beyond the Frost line and thus they are icy planetesimal counterparts to asteroids
Given that other jovian planets have cloud layers that are similar to Jupiter's, why are the clouds different colors?
- different compounds make clouds of different colors - planets closer to the sun are warmer - ammonia clouds form at similar temperatures on Jupiter and Saturn, but deeper in Saturn due to its lower temperatures
what are Jovian planets like on the inside?
- differentiated, like terrestrial planets -- meaning the heavier elements are towards the core and the lighter elements are toward the surface - no solid surface - cores (~ 10 Earth masses) are made of hydrogen compounds, metals, and rock
What are Hot Jupiters?
- exoplanets that are closer to their star than our own Jupiter is to our Sun
How do spectral types depend on stellar composition (star's composition)?
- for example, how much H or He is present
How did comets in the Kuiper Belt form?
- formed as icy planetesimals beyond the orbit of Neptune: flat plane, aligned with the plane planetary orbits and thus orbited in the same direction as the planets - there was not enough matter out there to build up a giant planet - There are wide range of sizes of comets
how did comets in the Oort Cloud form?
- formed as part of the group of icy planetesimals that made the Jovian plants - But they were kicked out to the outer solar system by gravitational close encounters with Jovian planets -- this resulted in random orbit direction, they were not close enough to the plane of planetary orbits to go all in one, uniform, direction like those in the Kuiper Belt
Did an impact kill the dinosaurs?
- fossil records show occasional large dips in the number of species -- means there must have been periodic, mass extinctions - most recent large dip (aka mass extinction probably) was 65 million years ago, that ended the reign of the dinosaurs
how are elements that make up the earth's atmosphere freed from rocks and into the atmosphere?
- geological activity (mostly volcanoes) vents the gases into the air that eventually make up the atmosphere
How do Giants and Supergiants compare to main-sequence stars?
- giants and supergiants are more massive, more luminous, but cooler than main-sequence stars
why can't continuous contraction (conversion of gravitational potential energy into thermal energy) be a reasonable explanation for the source of the Sun's energy?
- gravitational contraction made the Sun hot, but could only keep it hot for around 25 million years.
In summary, what are the characteristics of high mass main-sequence stars?
- high luminosity - short-lived - large radius - blue
the layers in the interior of the jovian planets are different between Uranus & Neptune, and Jupiter and Saturn. Why?
- high pressures inside Jupiter and Saturn cause the phases of hydrogen to change with depth - hydrogen acts like a metal at great pressures because its electrons move freely and becomes a conductor - lower pressures inside Uranus and Neptune mean there is no metallic hydrogen, as there is near the cores of Jupiter and Saturn
What is required to be able to excite electrons to reach high energy levels?
- high temperature
Why are high temperatures necessary for there to be nuclear fusion?
- high temperatures means high molecular activity - with high molecular activity, there are higher molecular speeds. At higher molecular speeds, nuclei are able to overcome the electromagnetic repulsion force that prevents them from combining at lower speeds
how are historical / prehistorical concentrations of CO2 measured?
- historical / prehistorical concentrations of CO2 are measured from bubbles trapped in layers of ice cores
What creates clouds on Jupiter?
- hydrogen compounds
What happens to electrons if temperatures are too high?
- if temperature is too high, electrons may escape the atom (called ionization), so that there will be no absorption or emission lines
In general, how do we measure stellar luminosities?
- if we measure a star's apparent brightness and distance, we can compute its luminosity with the inverse square law for light - we can infer distance using parallax
How is the surface of planets originally shaped?
- impacts by asteroids, comets, and meteorites originally shaped the surface of terrestrial planets, especially during the period of heavy bombardment
Why is light interaction with matter important?
- interactions between light and matter determine the appearance and color of everything around us - a mirror reflects all colors of visible light - a red chair is red because it scatters red light but absorbs all other colors - snow absorbs some light, which aids the melting of the snow, but it scatters most light -- hence why snow is often times extremely blinding - a glass window transmits all colors of visible light in the same manner that a mirror reflects all colors of visible light
What is an star or planets center of mass?
- it is an imaginary point that a star or a planet will orbit around due to the gravitational tugs of either the orbiting planet or the "stationary" star - The Sun, for example, orbits around a tiny center of mass as does Jupiter -- Jupiter evolves around the Sun, its center of mass - The Sun orbits its center of mass wit the same period as Jupiter orbits its own center of mass (i.e. the Sun), but because the mass of the Sun is much larger than the mass of Jupiter, it has a lower acceleration and therefore a much smaller orbit -- so small that it seems as if it is not even moving
what is Olympus Mons?
- it is the largest volcano (or mountain) in the solar system and is located on the surface of Mars
what does it mean for a star when its mass is 10 times the mass of the sun?
- it means that the star has 10 times as much fuel as the sun, but that its luminosity is 10,000 times higher than the Sun, so it is consuming fuel 10,000 times faster than the Sun, meaning it will have lifespan much shorter than that of the Sun, around 10 million years
Why did the climate change on Mars?
- it no longer had an atmosphere that could support liquid water. What happened? - its magnetic field protected the early martian atmosphere - as Mars' interior cooled and solidified, the magnetic field weakened, and the solar wind stripped away and destroyed the atmosphere - this process was compounded by reduced volcanic out gassing (because interior was cooled) and low escape speed (because of the small size of Mars)
How was that HUGE canyon streaking across the surface of Mars formed?
- it probably formed as a result of of an ancient tectonic rift
What did the UMD-led mission in 2005 to a comet show?
- it showed that comets are porous, with an average density of 0.5 gm / cm^3
what would happen to a star if it tried to grow to more massive than 150 times more massive than the Sun?
- it would explode - scientists are still trying to figure out why this is
What are the jovian planets like on the inside?
- layered interiors with very high pressure and cores made of rock, metals, and hydrogen compounds - very high pressure in Jupiter and Saturn that can produce metallic hydrogen
How long does it generally take for a massive, main sequence star to exhaust its hydrogen?
- less than 30 million years
where did oxygen in our atmosphere come from?
- life itself! Oxygen is very reactive and is quickly removed from the atmosphere by oxidation of rocks. Presence of significant oxygen in the atmosphere is a clear sign of life
In summary, what are the characteristics of low mass main-sequence stars?
- low luminosity - long-lived - small radius - Red
In general, why do low-mass stars on the main sequence have longer life spans/
- low-mass stars are less hot in the core since there is less mass to support against gravity
What is luminosity?
- luminosity is the amount of power that a star radiates - luminosity is an intrinsic property of a star - measured in watts, which is energy per second
what is the range of luminosity?
- luminosity of a star can be anywhere between 10^-4 times the luminosity of the Sun to 10^6 times the luminosity of the Sun, which means a star's luminosity can range from anywhere between .001 times that of the sun to 1,000,000 times that of the Sun
what protects an atmosphere from solar winds?
- magnetic fields. magnetic fields help protect the planet's atmosphere from solar winds
How can mass be determined?
- mass can be determined from period (p) and average separation (a) between two stars in a binary star orbit
what can we calculate once we have an asteroids mass?
- mass lets us calculate density, which we then can infer its composition -- D= m/v
What do mass measurements of main-sequence stars show?
- mass measurements of MAIN -SEQUENCE stars show that the hot, blue stars are much more massive than the cool red ones
In general, why do massive stars on the main sequence have shorter life spans?
- massive stars must be hotter in the core to provide enough pressure to support greater mass of star against gravity
What is the color and surface temperature of medium temperature stars?
- medium stars are yellow or white and have surface temperatures of about 6,000 K -- this is where the Sun lands
Looking at a photograph, how can you tell you are looking at a molecular cloud?
- molecular clouds, as viewed through a photograph, are those dark patches where it seems like no stars are shining -- these are the star forming, massive, molecular clouds where light cannot penetrate
How massive are most massive stars?
- most massive stars are 100 times the mass of the Sun
where is most of the CO2 on earth found?
- most of the CO2 on Earth is actually buried in the ground, hence why we need volcanoes and volcanic vents to release it into the atmosphere to replenish the atmosphere
Why aren't the big variations in spectral type caused by composition?
- most stars are 70% H and 28% He, so the big variations in spectral type are NOT due to compositional differences, but due more to temperature
What is the composition of Uranus and Neptune?
- mostly hydrogen compounds - H2O (water) - CH4 (methane) - NH3 (ammonia) - some H, He, and rock
Why is it so important for earth to have a magnetic field?
- on earth, if it were not for our magnetic field, the solar winds would not only destroy our atmosphere, but it would allow the harmful gamma rays and ultraviolet rays of the Sun to reach earth and burn us alive -- even if we could somehow survive the effects of the gamma and ultraviolet rays, we would have no water, as it would all evaporate, and we would have extreme temperatures like Mercury
What is the Doppler Method?
- one of three methods of indirect exoplanet detection by which we can measure a star's Doppler Shift, that in turn will tell us the star's motion toward and away from us, which we can then deduce is the result of a gravitational tug from an exoplanet and also measure how close or far that exoplanet may be from the star depending on how strong the tug is and how frequent the star's Doppler Shift transitions between blue and red light
What is the Transit Method?
- one of three methods of indirect exoplanet detection by which we can measure the effects of the exoplanet on the light emitted from the star, which can happen if the exoplanet partially blocks light from the star -- this is called a Transit
What is Energy Balance?
- one of two processes by which the Sun is stable - Energy Balance is reached when the rate at which energy radiates from the surface of the Sun (i.e. its luminosity) is balanced by the rate at which energy is released by fusion in the core
Why are most asteroids found in the asteroid belt between Mars and Jupiter?
- only rocky / metallic planetesimals could form inside the Frost Line - Due to its mass, Jupiter's gravity tugs on these asteroids, stirring up the region and preventing these asteroids from ever collection / accreting into a planet
Why does Titan have an atmosphere?
- probably because it is so massive (for a moon) and so far from the Sun
What do plate tectonics do?
- recycle the ocean crust - move continents - create rift canyons - build mountains and continents - shift locations of volcanoes
How does Mass play a role in geological activity. More specifically, in smaller planets?
- smaller planets cool off faster (chicken vs. turkey), so their interiors hardened and became more rigid faster
What is the surface of Charon like?
- smooth regions that resemble the lunar maria (on the Moon), suggesting the eruption of "lava", which in the case of Pluto might be water that froze, like lava that solidified and formed new surfaces
What are solar winds?
- solar winds are a flow of charged particles coming from the Corona of the Sun
How do solar winds destroy an atmosphere?
- solar winds consist of charged particles from the Sun that move at speeds of 100 km/sec, which an erode the atmosphere
What is an asteroid's composition?
- some asteroids are solid - others are just piles of rubble held together loosely by weak gravity forces - most asteroids are rubble piles that look solid, but are really just a pile of rocks held together by VERY weak gravity
In general, what causes solar activity?
- stretching and twisting of magnetic field lines near the Sun's surface causes solar activity
what are the Northern Lights?
- the Northern Lights are aurorae, which is a result of deflected charged particles (i.e. solar winds) bouncing off of our magnetic fields
How does a planet's close proximity to the Sun, and its mass, contribute to its lose of atmosphere?
- the Sun heats the atmosphere, causing atoms to move very fast. As temperature increases, atoms move faster, and thus eventually exceed the escape speed of the planet, escaping into space - so planets that are too hot (because they are too close to the Sun like Mercury) OR have too low escape speed (due to low mass, i.e. Mercury and Mars) ten to lose their atmospheres faster
How do radiating stars exemplify conservation of energy?
- the amount of luminosity passing through the entire area of each sphere is the same - energy radiated from a star in space is not diluted by any external object in the vacuum of space. Thus, the further we get from the star, the amount of energy radiated remains the same, just now it is more spread out the further we go, thus it is more concentrated and brighter the closer in and the less concentrated and less bright the further out we go
How does the Greenhouse effect work?
- the atmosphere traps infrared light near the surface (i.e. the radiation of energy in the infrared that the surface gets from the visible light that makes it through the atmosphere), acting like a greenhouse or blanket and making the atmosphere and the surface warm
How dense is the Sun?
- the average density of the Sun is about 1 gm/cc, which is similar to the density of water - at its surface, the Sun's density is less than our atmosphere
what do you notice about the composition of the materials in the interior of a jovian planet as you move from surface to core?
- the elements become more solid as we move from surface to core. Compression increases the further down you go, thus elements will become more solid
What does Newton's 3rd Law of Motion (action - reaction) have to do with exoplanet detection?
- the gravitational force (tug) of a planet pulling on a star is equal to that of the star pulling on the planet, but in the opposite direction
how does the mass of a main-sequence star determine that star's luminosity and temperature?
- the greater the mass of the star, the greater the gravity, so the central pressure required to balance gravity must be larger - larger amounts of pressure means more compression, thus higher temperatue - higher temperature means much higher fusion rates - Much higher fusion rates means more luminosity
Venus has surface temperatures of around 470 C. Why so hot?
- the greenhouse effect, due to enormously thick atmosphere that is 100x denser than that of earth's and is made mostly of carbon dioxide. - without it, Venus' surface would be below 0 degrees (i.e. below freezing).
what is the interstellar medium like? What is it made up of?
- the interstellar medium is very diffuse, meaning it is spread out over a large area and is not concentrated - the interstellar medium is made up of mostly H and He
Why are electrons forced to move faster when there are fewer quantum states available?
- the laws of quantum mechanics prohibit two electrons from occupying the same state in the same place (i.e. two people cannot sit comfortably in one chair). The speed of electrons increases as density increases (density being more people without chairs, more electrons without quantum states), so pressure increases, regardless of temperature - meaning as the amount of chairs that are taken away increases, more movement will happen and thus more pressure -- this is not dependent on temperature but rather on density (i.e. space)
What does the mass of a main-sequence star determine?
- the mass of a main-sequence star determines its luminosity and temperature
What is the range of masses of a star?
- the masses of a star can range from anywhere between 208 times the mass of the Sun t around 100 times the mass of the Sun
What is the composition of the nucleus (head) of a comet?
- the nucleus of a comet is a "dirty" (dusty), icy (water, CO2), "snowball", typically a few km in diameter (about the size of an average mountain on earth)
What does the number and appearance of craters tell us?
- the number and appearance of craters tells us the age of planetary surfaces, and thus the relative age of a planet - lots of craters tells us surfaces are very old, meaning they have been exposed to a lot of impacts, period after period from the period of Heavy Bombardment to all the smaller ones after, but varying densities of craters tells us some regions are younger than others and have erased their craters through weathering down or through volcanoes in the past
In general, what happens after stars leave the main sequence?
- the stars that have finished fusing H to He in their cores are no longer on the main sequence - all stars become larger and redder after exhausting their core hydrogen: they become giants and supergiants - most stars end up small and white after fusion has completely ceased: they then become white dwarfs
what is the range of temperature for a star?
- the surface temperature of the coolest stars are around 3,000 K while the surface temperatures of the hottest stars are around 50,000 K
How does new surface depend on the composition of lava?
- the thickest lava will make steep-sloped volcanoes. This makes sense as the thicker the lava it is, the slower it will run down hill, and thus the more time there is for the lava to solidify in the place that it is in (i.e. closer to the summit) - slightly runnier lava makes shallow-sloped volcanoes, such as Olympus Mons on Mars - very runny lava makes flat volcanic plains like the ones seen on the Moon; they look like long, winding channels. This makes sense as the runnier it is the faster it will make it down the mountain and the more distance it will cover and therefore the more spread out it will be when it solidifies
Direct mass measurements are only possible for...
- ...stars in a binary system
What is the range of mass for low-mass stars?
- 0.4 times the mass of the Sun to 4 times the mass of the Sun
How much has earth's average temperature increased in the past 50 years?
- 0.5 C
Accepting nuclear energy as the source of the Sun's energy, what is the predicted lifespan of the Sun?
- 10 billion years, (4.6 billion of which have gone by already)
How big was the meteorite (asteroid or comet) that is believed to have ended the dinosaurs?
- 10 km in size - a 10 km meteorite (asteroid or comet) is believed to have ended the reign of the dinosaurs - a meteorite that large would have sent large amounts of debris into the atmosphere - debris would have greatly reduced the sunlight's ability to reach the surface of the Earth for many months - this would have resulted in climate change that may have led to the mass extinctions as dinosaurs starved to death
What is the threshold temperature in order for there to be molecular lines (i.e. absorption or emission lines)?
- 3,000 K - above 3,000 K it is too hot for molecules, so there are no absorption or emission lines - below 3,000 K, molecules can exist, so we can have molecular lines
What is the luminosity of the Sun?
- 4 x 10^26
What is the formula for the area of a square
- 4(pi)r^2
What is the compositional make up of the Sun?
- 70% H - 28% He - 2% heavier elements (metals, rock)
What is the range of mass for high-mass stars?
- 8.0 times the mass of the Sun to 100+ times the mass of the Sun
What is a Hertzsprung-Russell Diagram?
- A HR diagram plots the luminosity and temperature of many stars
where does it protostar get its energy? In what way does that contrast from a main-sequence star?
- A protostar gets its energy from gravitational contraction - a main-sequence star gets its energy from fusion
besides stellar temperatures, what else do absorption lines tell us?
- Absorption lines in a star's spectrum tell us its ionization level or reveal the presence of molecules, which depend on temperature
What is a more reliable and effective way of measuring stellar temperatures?
- Absorption lines in the spectrum of a star, caused by slightly cooler gas overlying the slightly hotter opaque regions producing continuous spectrum, can yield very precise temperatures
What is another source of cracking in Europa's surface?
- Europa may have a 100 km thick ocean under its icy crust - rising plums of warm water may sometimes create lakes within the ice, causing the crust above to crack - This explains the surface terrain that looks like a humble of icebergs suspended in a place where liquid or slushy water froze
Why will the footprints of astronauts forever be on the Moon?
- Footprints will forever be on the surface of the Moon because the interior of the Moon, as result of its mass, has cooled off and thus is considered geologically dead. Since it is geologically dead, there is no geological activity, which means no winds, no volcanoes, and no water to disrupt or change the footprints on the surface, or anything for that matter
For geological activity to occur, what cannot happen?
- For geological activity to occur, the lithosphere (which is the crust and part of the upper mantle) cannot extend too far below the surface, because then the convection cells that force magma through volcanoes and create the mountains for volcanoes would not be able to happen
What happens if some pressure force stops contraction BEFORE the required threshold temperature of 10^7 K is met?
- Fusion never occurs
Through what means can a star's motion reveal the presence of orbiting planets?
- GRAVITATIONAL TUGS
in order from most destructive (shorter wavelength) to least destructive (longer wavelength), list the wavelengths that fall in between gamma and radio waves
- Gamma rays - X-rays (shorter) - Ultraviolet radiation - Visible light - Infrared radiation - Microwaves (longer) - Radio waves
What is unique about Ganymede?
- Ganymede is the largest moon in the solar system
where is the likely impact site of the meteorite that ended the dinosaurs?
- Geologists have found a large subsurface crater about 65 million years old in Mexico, along with other evidence of blast around the Gulf of Mexico
How did the Sun get to be so hot?
- Gravitational contraction (compression) of an interstellar cloud from one light year across down to the size of a star, about 1 light-second across! - that's a lot of compression! Remember that when things contract, pressure increases and the entirety heats up (cotton ball in pressure tube). So, when this enormous compression was happening, gravitational potential energy was being converted into thermal energy. This caused things to get hot - it was hottest in the center (around 15 million K) where enormous compression was greatest
What is unique about Jupiter's internal heat? Where does it get its energy?
- Jupiter radiates twice as much energy as it receives from the Sun - energy probably comes from the slow contraction of its interior that releases potential energy outwards
In sum, what is the difference between a Kuiper Belt comet and an Oort Cloud comet?
- Kuiper Belt comets are the planetesimals that formed outside the orbit of Neptune where there was not enough matter to build up a giant planet - Oort Cloud comets were members of the group of planetesimals that formed the Jovian planets, but were ejected from orbits near Jovian planets
What is a dwarf planet?
- Largest planetesimals in the Kuiper belt - like planets, they are massive enough so that gravity has made them round and spherical - like planets, (but not like moons), they orbit the Sun - Unlike planets, they are not massive enough to "own" their orbital neighborhood, but rather they share it with other objects that may be similar in size
how small are most small stars?
- Least massive stars are .08 times the mass of the Sun
So why does degeneracy pressure come into play in the place of pressure from fusion?
- Like we said, degeneracy pressure is dependent only on density and space, so if pressure from fusion is not available, because the temperature threshold was never met, then gravity will contract the protostar to a point where degeneracy pressure kicks in because it has been compressed so much.
What often connects sunspots? Why are we able to see this?
- Loops of bright gas often connect sunspot pairs - pairs of sunspots are connected by tightly wound magnetic field lines. These tightly wound magnetic field lines trap gas, which is what we see
How can luminosity be determined?
- Luminosity can be determined only after you have calculated apparent brightness and distance - then, you must use the formula: L = 4(pi)(distance)^2 x Apparent Brightness
What does Mercury's steep cliffs tell us?
- Mercury has an unusually large iron core relative to the other terrestrial planets - Mercury's core shrank as it cooled, compressing the surface - this created long cliffs as some portions of the crust were forced to slide under others -- today we see long, steep cliffs created by this unusual crustal movement
What is Miranda and what does it show?
- Miranda is a medium moon of uranus - Miranda has large tectonic features and few craters -- possibly indicating an episode of tidal heating after the period of heavy bombardment
Where are most asteroids located in the solar system?
- Most asteroids can be found in the Asteroid Belt between Mars and Jupiter
What are the orbits and sizes of the exoplanets that have been detected so far like?
- Most of the detected exoplanets have orbits that are smaller than Jupiter's
What is the composition of Jupiter and Saturn?
- Mostly H and He, less than 2% of other, heavier elements like rock and metals
What are the surface features of Mars?
- Much of Mars' northern hemisphere is covered by volcanoes and lava plains with some erosion features - Much of Mars' southern hemisphere is covered by ancient craters, which tells us that there is generally no volcanic activity because if there was, the lava from the volcanoes would have covered the craters with new surfaces
Would adding the masses of all the asteroids in the solar system add up to a small terrestrial planet?
- NO - this rejects the theory that all the asteroids once comprised a planet, or rather are pieces of a planet that failed to form - Asteroids are primarily just the leftovers from accretion
how can we calculate the mass of a Jovian planet? What is the equation?
- Newton's rendition of Kepler's 3rd Law: P^2 (M1 + M2) = a^3 - since the mass of, say Jupiter, is much greater than the mass of the Moon, in some instances we can ignore the second mass calculation: P^2(M) = a^3
Is the interstellar medium denser than our atmosphere?
- No, some regions are 1,000 times denser than average (molecular clouds), but still more than a trillion times less dense than our atmosphere
does the Sun's motion around the solar system's center of mass depend on only Jupiter's gravitational tug?
- No, the Sun's motion around the solar system's center of mass depends on tugs from all the planets, not just Jupiter
What is the hottest spectral type and what is the coolest?
- O is the hottest (furthest on the left) - M is the coolest (furthest on the right)
what are the 7 different spectral types?
- O, B, A, F, G, K, M
But why is Io's orbit so elliptical as to cause tidal heating?
- ORBITAL RESONANCES - every 7 days, the other three moons of Jupiter line up with Io -- the tugs add up over time, making all 4 orbits of Jupiter's moons elliptical, especially Io
Are there more low-mass stars or high-mass stars?
- Observations of star clusters show that star formation makes many more low-mass stars than high-mass stars
what is another way in which a comet may make it into the inner solar system (i.e. inside the Frost Line)?
- Occasionally, these comets in the outer solar system (both Kuiper and Oort), pass close to each other in their orbits, and their orbits can get re-directed into the inner solar system, which is when they pass close to the Sun and form jet streams that we see and study from Earth
What is different about the way in which the HR diagram plots temperature?
- On the HR diagram, temperature, on the x-axis, has the hottest temperatures on the left and the cooler temperatures on the right
Where are convection cells on the Sun visible?
- On the photosphere. - at the photosphere, we can actually see the tops of the convective cells/parcels of gas (hot and bright spots) and falling (cooler, darker, denser areas between the bright spots)
What is gravitational equilibrium?
- One of two process by which the Sun is stable - Gravitational equilibrium is reached when energy supplied by fusion in the core maintains the temperature (and therefore the gas pressure) needed to counter-balance the inward crush of gravity - in other words, gravitational equilibrium is reached the energy output balances the force of gravity and thus the star is stable and no longer contracting nor expanding
How does light interact with opaque objects?
- Opaque objects absorb light at continuous wavelengths - Opaque objects emit light at continuous wavelengths (thermal radiation -- human bodies glowing in the infrared is an example of an opaque object emitting thermal radiation)
What are the measurable properties of exoplanets?
- Orbital period, distance, and shape - mass, size, and density - atmospheric properties, temperature of the surface
What has Jupiter done to these asteroids over time?
- Over time, Jupiter has ejected most of these asteroids from the belt. These rejected asteroids contributed to the period of heavy bombardment and are major drivers of ongoing impacts today
how do we measure the distance of a star?
- PARALLAX
How can we use parallax to determine distance?
- Parallax is the apparent shift in position of a nearby object against a background of more distant objects - Apparent positions of nearest stars shift by about an arc-second as earth orbits the sun - Parallax angle depends on distance - parallax is measured by comparing snapshots taken at different times and measuring the shift in ANGLE to that star
How is oxygen created for it to exist in our atmosphere?
- Photosynthetic life in the oceans creates O2 - O2 and UV creates O3 (the ozone layer) - the ozone layer makes the surface safe for living things - photosynthetic life on land adds O2 to the atmosphere
What is the surface temperature and geological activity like on Pluto?
- Pluto is extremely cold, around 40 K, which makes sense because it is so far from the Sun - The New Horizons spacecraft revealed a surprisingly active geology, which we can tell by the fact that it has mountains that are less than 100 million years old - Pluto's active geology is confusing because there is no tidal heating (does not have an extremely elliptical orbit), so scientists are still unsure why it is so active - Pluto also has an atmosphere
What do the different cloud layers on Jupiter correspond to?
- The different cloud layers correspond to freezing points of different hydrogen compounds - in the thermosphere, higher in the atmosphere, conditions are normal - one step lower, in the stratosphere, it is cold enough for ammonia to condense to form clouds. It is also cold enough for ammonium hydrosulfide to condense to form clouds - one step lower, in the troposphere, it is cold enough for water to condense to form clouds
What is the interstellar medium?
- The interstellar medium is the gas and dust between the stars
what are the luminosities of the most luminous stars?
- The most luminous stars have luminosities that are equal to about 10^6 times the luminosity of the Sun, so their luminosities are a million times greater than that of the Sun
What does the orbital period of a binary star system depend on?
- The orbital period of a binary star system depends on strength of gravity, which depends on the mass of the stars
How do the orbits of exoplanets compare with the orbits of planets in our own solar system?
- The orbits of many exoplanets are much more elongated (more elliptical) than the orbits of planets in our own solar system - The orbits of most exoplanets are closer to their star than the Jovian planets are to our own sun
How does a transit inform us about the composition of that planet's atmosphere?
- The planet's upper atmosphere can block additional light at some wavelengths, telling us about the atmospheric composition of that exoplanet
What are the features and composition of Venus' atmosphere?
- Venus has an extremely thick atmosphere that is made up of mostly carbon dioxide - Venus' atmosphere is about 100 times MORE thick than earth's, meaning it has 100 times more atmospheric presence/gas than earth does - HUGE greenhouse effect, making the surfaces extremely hot - there is no molecular hydrogen - there is no liquid water on the surface now
in general, how do we measure stellar temperatures?
- a star's color and spectral type both reflect temperature, but color is generally not considered a reliable method for inferring stellar temperatures
What is Diffraction Grating?
- a surface with many parallel equidistant lines etched to block light at periodic intervals
How far out is the Kuiper Belt?
- about 100 AU at its furthest
How far out is the Oort Cloud?
- about 50,000 AU at its furthest
At what temperature can gravitational contraction of a protostar stop and nuclear fusion in the core begin in order to make the protostar a main-sequence star?
- above 10^7 K
What core temperature is necessary for fusion to start?
- above 10^7 K
What is the significance of the Main Sequence?
- all main sequence stars are fusing hydrogen to helium in their cores, like the Sun
What is the weather like on the jovian planets?
- all the jovian planets have strong winds and storms
Why is there no liquid water on Venus?
- all the liquid water evaporated due to the extreme greenhouse effect
What do the medium moons of Saturn show?
- almost all of the medium moons of Saturn show evidence of past volcanism and/or tectonics (both with ice, not lava), even though some have masses more than 1,000 times less than geologically dead Mercury
What is an Eclipsing Binary?
- an Eclipsing Binary is a binary system where we are close to orbital plane, so we can see light dip when one star passes in front of the other - Remember the graph of slide 31
what is apparent brightness?
- apparent brightness is the amount of starlight that reaches Earth - it is how bright the star appears to be to us on Earth
What does apparent brightness of a star depend on?
- apparent brightness of a star depends on both its luminosity and its distance from us - the further away the star is, the less bright it appears
how many comets are there in the Oort Cloud?
- as many as 100 billion
What are asteroids?
- asteroids are rocky leftovers (planetesimals) of planet formation
Why can we say that each type of atoms has a chemical fingerprint?
- because each type of atoms (elements such as H, He, O, C, etc.) has a unique set of energy levels - each transition between levels therefore corresponds to a unique photon energy, frequency, and wavelength, which appears as a "line" in a spectrum
Generally speaking, why does the Sun shine?
- because it is massive and hot
why is there less H and He on Uranus and Neptune?
- because the outer solar nebula had less gas to "feed" them
Why can't there be exoplanets with masses more than 10 times that of Jupiter?
- because then they would be considered a star
Why is Europa being called a possible water world?
- because tidal stresses cracked Europa's surface ice - Close up photos show double-ridged cracks, best explained by an icy crust moving upon a soft, or liquid, layer beneath it - Today stresses cause part of Europa's icy crust to slowly slide past each other - Frictional heating expands ice from here. forming a ridge...and my melt ice here, collapse the ridge center, forming a miniature canyon
In what ways is the Transit Method biased?
- the transit method favors detection of planets that are: 1. the tiny fraction that happen to be viewed edge-on, so that the planet passes between us (our view on earth) and the star -- we must first be in the same plane as the exoplanet and the star it is orbiting in order to measure its effects using the transit method (i.e. in order to see just how a transisting planet affects star light) 2. closer to a star (transits occur more frequently when a planet is closer to a star because of a faster orbit period) 3. Larger radius -- larger stars block more sunlight and have a bigger transit effect that is more easily identifiable
how common are exoplanets?
- there has been a recent surge in the number of exoplanets that have been detected - thousands of exoplanets have been detected. There are certainly billions in our galaxy that we cannot see as there are 100 billion stars in the galaxy and most probably have planets like our Sun
How many known exoplanets are there already?
- there have been more than 3,700 exoplanets confirmed already and more than 4,000 candidate exoplanets
How do we know that there was once water flow on mars?
- there is evidence that there was once water and streams on Mars as we have found rounded rocks and that "blue rock"v that can only have been formed by water erosion
It is clear that liquid water is gone from Mars (since its interior cooled), but why can't liquid water form on the surface now?
- there is not enough atmospheric pressure now to allow liquid water to form on its surface, like perhaps it did in the past when there was still interior heat for there to be volcanic activity and thus an atmosphere and thus enough pressure to form liquid water and regulate temperature to keep it in liquid form - there is also no molecular oxygen in what little atmosphere Mars has left, water (H2O) needs a molecule of oxygen
What is a result of the fact that star light cannot penetrate molecular clouds
- they are very cold (10-30 K) because no starlight is able to penetrate the inner workings of these clouds - molecules are able to form because these clouds are protected from ultraviolet light -- this is why they are called molecular clouds
How can thinking of a nebula gas cloud between Earth and the Sun help us understand how to infer the composition of an exoplanet's atmosphere?
- think of a cloud of nebula gas between the Earth and the Sun. By observing what kinds of wavelengths the nebula gas cloud absorbs and what kinds it emits, we can infer the composition of the nebula gas cloud itself
What is a Continuous Spectrum? How is it characterized? What are 2 examples of continuous spectrum?
- think smooth curve -- continuous, smooth, no interruptions Examples: - the spectrum of an opaque object spans all visible wavelengths, without interruption (continuous), with color depending on temperature. Stars are opaque, so they emit continuous spectra - Thermal radiation produces continuous spectrum, and allows us to measure temperature -- the hotter an object, the more light it emits at all frequencies and the shorter the wavelength at which it is brightest, which affects color
What does it mean when we say that the main sequence is a mass sequence?
- this means that even though the HR diagram is not plotting mass, I know where on the diagram to plot a star based on its mass
What is Tidal Heating?
- tidal eating is the squishing and stretching of a moon in its orbit around a larger planet -- this constant shifting of forms creates a lot of activity in the core of the Moon, leading to a lot of volcanoes like on Io
How does light interact with transparent objects?
- transparent objects pass light, but depending on composition, they may: 1. absorb light at discrete and varying wavelengths 2. emit light at discrete and varying wavelengths
How rare are major meteorite impacts on earth?
- very rare. Extinction level impacts happen many of millions of years apart - significant damage level meteorite impacts happen tens to hundreds of years apart - still, it is not a matter of IF, but rather WHEN
How does visible light warm us?
- visible light from the Sun passes through the atmosphere. A large fraction of it is absorbed by the Earth's surface and therefore warms the surface - Due to the temperature of the visible light that makes it through the atmosphere (about 300 K, 30 C, and 80 F), the surface of the earth radiates in the infrared
What can we deduce from measuring the orbit of an asteroid's moon?
- we can tell how massive the asteroid is -- what the mass of the asteroid is
What are the features and composition of Mars' atmosphere?
- what little atmosphere that Mars does have is made mostly of CO2, but there is so little atmosphere left that the greenhouse effect is less than Earth's - the atmosphere of Mars is 100 times less dense than earth's
What is degeneracy pressure?
- when the number of electrons approaches or exceeds the number of available quantum states, finding an available quantum state requires that the electrons move faster than they would otherwise. This extra motion creates more activity and thus more pressure - Degeneracy pressure is enough to replace pressure resulting from fusion - Think of the crowded room and chairs example
What is the main sequence on the HR diagram?
- where most stars fall on the HR diagram
How do white dwarfs compare to main-sequence stars?
- white dwarfs are less massive, less luminous, but hotter than main-sequence stars
What does a lack of fusion mean?
- without fusion, thermal pressure cannot stop contraction
So we know that the interstellar medium itself is not dense, is it very massive?
- yes, there are clouds in the interstellar medium -- called molecular clouds -- that can have masses that are 1,000 to 1 million times the mass of the Sun -- each molecular cloud has the raw material to make many stars at a time (star clusters)
What are the 3 requirements that an object must meet in order to be considered a planet?
1. Orbits the Sun 2. Massive enough so that gravity makes it spherical 3. Massive enough to clear out its own orbital neighborhood - Pluto and other dwarf planets like Eris do not satisfy requirement #3
What are the two differences that vary between Terrestrial planets so that their surfaces and atmospheres are different from one another?
1. Planet's Mass 2. Planet's Distance from the Sun
What are the 3 classes of Jovian Moons? What are their corresponding measurements?
1. Small Moons (<300 km) 2. Medium-sized Moons (300-1500 km) 3. Large Moons (>1500 km)
What are two ways that we can measure stellar temperatures?
1. Spectrum of a star 2. Spectral type of the star
What does the spectral type depend on? i.e. what does the strength of spectral lines depend on?
1. Star's composition 2. Temperature
What geological activities depend on planet mass? Why do they depend on a planet's mass?
1. Tectonics 2. Volcanism 3. Erosion All three of these geological activities depend on the retained interior heat of the planet, which depends on the mass of the planet 1. without interior heat you could not have tectonics 2. without interior heat you could not have magma and volcanoes, which replenish the atmosphere and give it the necessary gases, such as CO2, to regulate temperatures. Without interior heat, you would not have magnetic fields that protect against solar winds. 3. Without interior heat, you could not have the atmosphere and thus could not have weather, which means you could not have wind, water, ice and thus could not have erosion
What type terrestrial bodies, because of their small mass, have cooled off and are now considered "geologically dead"?
1. The Moon 2. Mercury
What is the formula for Apparent Brightness?
Brightness: Luminosity / 4(pi)(distance)^2
Star A and Star B have identical luminosities, but Star B is three times further from us. How does the brightness of Star B compare with that of Star A? a.) it would only be 1/3rd as bright b.) it would be only 1/6th as bright c.) it would be only 1/9th as bright d.) it would be three times brighter
C
Which of the following about Pluto is NOT true? a.) Massive enough to be spherical or round b.) Orbits the Sun c.) Massive enough to clear out its own orbital neighborhood d.) exhibits geological activity
C
Which of the following is NOT a reason it is hard to directly detect exoplanets? a.) they are far away b.) they are much fainter than their star c.) they do not emit visible light
C
In general, why are Jupiter's Galilean moons so geologically active?
Combination of: - icy composition, resulting in lower temperature threshold for liquid and gas phases (compared to rock) to be present - tidal heating, due to elliptical orbits driven by resonances in orbital periods of moons
What is the equation for Nuclear Potential Energy?
E = mc^2
why does Venus have so much CO2 in its atmosphere and earth has so little?
Earth - CO2 is vented into the atmosphere by volcanoes and (currently) by burning fossil fuels - Rain washes down atmospheric CO2 to the surface, where CO2 forms carbonate rocks on the ocean floor. Nearly all of the earth's CO2 is in rocks, with some buried in animals and plants -- almost all of Earth's CO2 is underground Venus - CO2 is vented into the atmosphere by volcanoes - because of its close proximity to the Sun, water cannot condensate and stars in the gaseous form. Since there is no liquid water, there is nothing to remove CO2 from the atmosphere -- CO2 is stuck forever in the atmosphere of Venus
What does I, II, III, IV, and V correspond to when talking about luminosity classes?
I = Supergiant II = Bright Giant III = Giant IV = Subgiant V = main sequence
what is a good mnemonic to help remember spectral types?
Oh, Be A Fine Girl, Kiss Me
How do you calculate the density of an exoplanet?
Planet Density = mass / volume - The Doppler Method gives us an accurate mass - The transit method gives us a radius, which we can then use to calculate the planet's volume
How does distance allow for earth to remain geologically active and have oceans?
Planets close to the Sun: - warm surfaces - no oceans, rain, snow, or ice (too hot for water vapor to condensate) - less erosion - hot atmosphere leads to more atmospheric escape Planets at intermediate distances from the Sun: - Surfaces at moderate temperatures - oceans, rain, snow, and ice - more erosion Planets far from the Sun - cool surfaces - ice and snow, but no rain or oceans (temperature is too cold for water to melt) - less erosion - earth is located at an optimal distance from the Sun in order for liquid water to exist
What are the differences between rocky planets and icy moons?
Rocky Planets - Rock melts at higher temperatures - Only most massive rocky planets have enough heat for geological activity (i.e. Earth and Venus) Icy Moons - Ice melts at lower temperatures - Tidal heating can melt internal ice, driving a lot of geological activity, more so than rocky planets
True or False: most massive stars that ever formed in the lifetime of the galaxy have used up their hydrogen and left the main sequence?
True
True or False: All wavelengths of electromagnetic radiation are considered light?
True. All wavelengths of electromagnetic radiation are considered light, they only differ in their waveLENGTH, which is the equivalent to their frequency or their energy per photon -- i.e. visible light is just a part of the spectrum where the wavelength is not too long and not too short enough for the human eye to detect, but there are shorter and longer wavelength on the spectrum that exist, the naked human eye cannot pick them up
True or False: most low-mass stars that ever formed in the lifetime of the galaxy are still here.
True. stars that are less massive than the sun have lifetimes longer than 10 billion years -- the galaxy is just about 10 billion years old
On Earth, where did the gases come from that make up the atmosphere?
there was lots of oxygen, carbon, and nitrogen in the rocks
Name two dwarf planets
1. Eris 2. Pluto
What does Newton's 2nd Law of Motion (F = ma) have to do with exoplanet detection?
- According to Newton's 2nd Law of Motion, the accelerations are inversely proportional to the masses - So a planet will move fast in a big orbit and the star will move slower in the little orbit, both orbiting their own center of mass with the same period - basically, by Newton's Second Law, because the bass of the star is much bigger than the planet's mass, its acceleration due to the equal force applied to it by the planet (the tug) will be much less than the acceleration of the less massive planet (same principle that explains why a large man on a skateboard will not move all that much compared to a small girl on a skateboard who will move a great deal when she pushes off of him)
How does our atmosphere protect us from x-rays and ultraviolet radiation?
- All X-ray light is absored very high in the atmosphere - Ultraviolet light is absorbed in the ozone (O3) - visible light is able to make it through the ozone and the atmosphere
Since comets are so far from the Sun (they are found in the Kuiper Belt and the Oort Cloud), then how do we sometimes see comets with our naked eyes from Earth?
- Although a vast majority of comets are far from the Sun, there is a small subset whose orbits are SO elliptical that it takes them inside 5 AU, where they can grow tails as the Sun heats the icy surface
What are the following like compositionally: Asteroid Comet
- Asteroids are rocky - Comets are icy
How do Orbital Resonances affect asteroids?
- Asteroids in orbital resonance with Jupiter experience periodic nudges - eventually, those nudges move asteroids out of resonant orbits, leaving gaps in the asteroid belt
During a transit, at most wavelengths, how much of the star's light does a planet block?
- At most wavelengths, the planet blocks about 2.5% of the star's light during a transit, telling us the planet's size
why are Uranus and Neptune blue?
- Because of methane. - Methane gas in Neptune and Uranus absorbs red light, but transmits blue light - Blue light reflects off of methane clouds, making those planets look blue - light of all colors comes from the Sun - Methane gas absorbs red light and transmits blue light - methane clouds reflect the blue light back into space, which is what we see
Why can't starlight penetrate molecular clouds?
- Because they are so MASSIVE
With the Doppler shift, what do the colors blue and red correspond to?
- Blue light means that the star is moving towards us -- makes sense because if a star is coming towards us, the wavelengths are getting shorter -- shorter wavelengths correspond to blue (hot colors and more destructive capabilities) - red light means that the star is moving away from us -- makes sense because if a star is moving away from us, the wavelengths are getting longer -- longer wavelengths correspond to red (cooler colors and less destructive capabilities)
What is Callisto known for being?
- Callisto is known as the "cratered iceball."
What are 3 unique things about Callisto?
- Callisto is the furthest orbit out from Jupiter (makes sense because it is an iceball) - Because Callisto is the furthest out, it does not feel the effects of orbital resonances, and so it does not have an elliptical orbit, and does not have tidal heating, and thus there is little geological activity - Callisto is also heavily cratered, indicating an old surface that nonetheless may hide a deeply buried ocean
What is unique about Ceres?
- Ceres has many mysterious bright spots on crater floors that might be ice, salt, or something else all together - Ceres also has a mountain that is 4 km tall and rises above otherwise bland surroundings, offering no clue to its origins - Ceres is also the closest dwarf planet to the Sun, located in the Asteroid belt
What is Ceres?
- Ceres used to be called an asteroid, now it has been classified as a dwarf planet
Why is solar activity annoying?
- Charged particles streaming from the Sun can be disruptive to electrical power grids and can disable communication satellites
Where did liquid water on earth come from?
- Comet impacts probably brought liquid water to Earth
What are the orbits of comets like?
- Comets are on extremely elliptical orbits
What are the layers of the Sun, starting from the core out?
- Core - Radiation Zone - Convection Zone - Photosphere - Chromosphere - Corona - Solar winds - Sun spots
How accurate are current techniques in measuring or detecting motion?
- Current techniques can measure motions as small as 1 m/s (walking speed)
If fusion never occurs, and contraction must be stopped, what steps in to counter-balance gravitational contraction if the threshold temperature for fusion is never met?
- DEGENERACY PRESSURE
Generally, what do direct and indirect methods of exoplanet detection consist of?
- Direct: photos or spectra of the exoplanet itself - Indirect: measurements of the effects of the exoplanet on the properties of the star which the exoplanet is orbiting
what was the first ever detected exoplanet? how did we know?
- Doppler shifts of the star 51 Pegasi indirectly revealed a planet with a 4-day orbit period - This short period means that the planet has a small orbital distance - 51 Pegasi's planet was discovered in 1995
What produces the lines that we see in spectra?
- Electrons in atoms are restricted to particular energy levels - The only allowed changes in energy are those corresponding to a transition between energy levels - when an electron transitions from one energy level to another, a photon is emitted or absorbed -- that is what we see. If it is emitted, we see an emission line and if it is absorbed, we see an absorption line (i.e. a gap in the spectra)
What is a Coronal Mass ejection?
- Eruption of solar winds - Coronal mass ejections send bursts of energetic charged particles out through the solar system
What is Europa known for being?
- Europa is known for possibly being a water world
Describe how a star is made
- Gravity constantly wants to make a cloud or star contracted and compressed - As the molecular gas cloud is being compressed, it heats up, creating pressure that is soon able to counter-balance the inward force of gravity (i.e. the epic battle between gravity and pressure) - Gravity can create a star only if it can overcome this force of thermal pressure. Gravity is greater in regions where density is higher, because gravity depends on mass and the inverse square of size. Pressure is lower in colder regions, because remember that gas pressure is proportional to temperature (as seen in the fact that increasing thermal pressure was able to create enough pressure to oppose gravity) - So stars form in dense, cold clouds of molecular gas where pressure is not great enough to counter-balance gravity - As dense, cold clouds contract. gravitational potential energy is converted into thermal energy, but since the cloud is transparent (as seen in the infrared), heat radiation escapes and the cloud stays relatively cold. - since it is cold, pressure does not build enough to slow the collapse until the cloud becomes opaque to its heat radiation, which does not happen until the cloud ha shrunken to perhaps 10 times the diameter of the Sun. Then pressure can build fast enough to catch up with increasing gravity, and so contraction slows down -- this is called a Protostar
Describe the process of how a LOW-MASS star dies
- H fusion in the core ends - H shell fusion begins - As H shell fusion starts the core starts to collapse, raising the temperature - Because of this new source of energy and sudden raise in temperature, He fusion in the core begins - With He fusion in the core, outer layers of the star puff out - because of this expanding of the outer layers of the star, surface temperatures cool down and thus turn Red -- the star is now a Red Giant - He fusion in the core ends - When He fusion in the core ends, the outer layers of the star are discarded in a planetary nebula - Core collapses - if the mass of the collapsed CORE is less than 1.4 times the mass of the Sun, then it is considered a White Dwarf - STUDY FIGURE 9.25
Describe the process of how a HIGH-MASS star dies
- H fusion in the core ends - Shell fusion of both H and He starts - outer layers puff out, surface expands and cools -- the star is now a Red Supergiant - Because temperatures are now cool, the core contracts and temperatures heat up again and shell fusion re-starts -- this process happens over and over until there is no longer any more He or H in the shell - Once all of the H and He in the shell have been burned, iron core collapses (no fusion means no way to fight against gravity) - Outer layers explode (force of gravity pushing down, causing collapse, leads to "bounce" effect) - supernova - Core collapses - if the mass of the collapsed CORE is between 1.4 and 3.0 times the mass of the Sun, then we get a neutron star - If the mass of the collapsed CORE is greater than 3.0 times the mass of the Sun, then we get a black hole - STUDY FIGURE 9.25
What enables nuclear fusion? What must be present in order for nuclear fusion to be made possible?
- HIGH TEMPERATURES -
How does a coal poker and a fire exemplify color, temperature, and visible light on the electromagnetic spectrum?
- Held above the flames, it is hot and glowing in the infrared, but not yet hot enough to glow in visible light - held closer to the flames, and it gets hotter, now it is glowing in visible light, but only hot enough to be glowing in the color red - held in the flames / bottom of the fire and now it becomes hot enough to blow in the white and blue area
What was found on the surface of Titan in 2005?
- Huygens Probe found liquid methane lakes and "rocks" made of ice on the surface of Titan
What did the track and billiard balls demonstration in class show?
- IT demonstrated that at high speeds, nuclei (billiard balls) are able to overcome the electromagnetic repulsion force of atoms (hill in the track) in order to combine and fuse -With a slow roll, the ball could not make it over the large hump in the track (i.e. the electromagnetic repulsion of the other nuclei), but with a faster speed (due to higher temperatures that increase molecular activity and speed), the billiard ball (nuclei) was able to overcome that electromagnetic repulsion hump and fuse with the other ball (nuclei)
In general, how do we measure stellar masses?
- If we can measure the orbital period (P) and the average orbital separation of the system (a), then we can measure the mass of the stars
Where is Ceres located?
- In the Asteroid Belt
Why does the core of the Sun not as pressurized or solid as that of Jupiter because of its mass?
- In the core of the Sun, the density is more than 10 times that of iron, but it is so hot that it is a gas
Why is the Radiation Zone an ineffective way for energy to be radiated? Why does it take so long for energy from the core to be radiated out by photons?
- In the radiation zone, the photons are redirected and diffused = think drunken walk - it takes around 100,000 years just for a photon to make it to space. - this points to the importance of the convection zone
what does iridium tell us about dinosaur extinction?
- In the upper layers of rock (i.e. the younger rock layers), there are no dinosaur fossils - Beneath the younger layer, thin 65 million year old later, contains iridium, which is rare on Earth but not in meteorites (which is believed to have killed the dinosaurs) - Right below the 65 million year old iridium layer, in the older rock layers, we have found dinosaur fossils
What is Io known for being?
- Io is known for being the most volcanically active body in the solar system - volcanoes are constantly changing the surface of Io
Why wouldn't we be here if weren't for these major impacts?
- It was, most likely, a major impact of a comet that brought water initially to Earth - probably a major impact of a mateorite that killed the dinosaurs and made space for mammals like us to rise and dominate in their place
what happens when a comet becomes "active" i.e. when it starts to develop jet streams?
- Jets of dusty water and CO2 vapor form if the comet approaches the Sun within the orbits of the terrestrial planets (i.e. inside the Frost Line) - If a comet is showing a long jet stream, you can infer that it is inside the Frost Line and close to the Sun
Are jovian planets all alike?
- Jupiter and Saturn are mostly H and He gas - Uranus and Neptune are mostly H compounds - there is less H and He on Uranus and Neptune
What is Pluto's moon? What is unique about it?
- Pluto's moon is called Charon - Charon is nearly as large as Pluto itself (probably made by a major impact)
How long has the Sun been shining?
- Radioactive dating of meteorites tell us that the solar system (including the Sun) formed 4.6 billion years ago - There is extensive evidence that the Sun has been shining at approximately its current luminosity (within 50%) since then
what color is associated with longer wavelengths? What color is associated with shorter wavelengths? What color represents the shortest wavelength?
- Red is associated with longer wavelengths, blue is generally associated with shorter wavelengths - violet is associated with the shortest wavelength (hence, ultraviolet is the next shortest wavelength after visible light)
Why isn't judging stellar temperatures solely by color not an always effective or reliable way of measurement?
- Reddening from interstellar dust can redden the color of a star, so it is hard to get a precise temperature read from color alone
Why does Jupiter have bands?
- Reddish clouds of ammonium hydrosulfide blanket the entire planet at low altitudes - Rising air forms white ammonia clouds at higher altitudes - Jupiter's strong Coriolis Effect diverts the north-south air flow into strong east-west winds - Ammonia "snow" falls from these high altitude clouds - So descending air therefore lacks ammonia and ammonia clouds, allowing us to see down to the reddish clouds below - Red bands that we see are lower-altitude clouds, which are warmer and therefore brighter in the infrared - White bands that we see are higher-altitude clouds, which are cooler and therefore emit less light in the infrared
If Uranus and Neptune are smaller than Saturn, yet more dense than Saturn (because of less H and He), then why aren't Uranus and Neptune denser than Jupiter?
- Remember: the greater the mass, the more compressed. The more compressed, the greater the density - Adding mass to a jovian planet compresses the underlying gas layers, creating density - Imagine: adding pillows to a stack may at first increase its height, but eventually, it just compresses the overall stack, making its density greater and compression greater at the bottom of the stack. Similarly, adding mass to a jovian planet eventually will increase its density rather than increasing just its radius - Thus, although one may reasonably conclude that Uranus and Neptune are denser than Jupiter because they have less H and He than Jupiter, they would be wrong just because of the sheer size of Jupiter that makes it denser than both Uranus and Neptune -- Saturn is not nearly as massive as Jupiter and thus does not have this issue
Why does Venus lack oceans?
- Runaway Greenhouse Effect
What explains why the Sun is stable, rather than exploding apart like a bomb?
- SOLAR THERMOSTAT
What is unique about Saturn and Neptune's internal heat? Where do they get their energy?
- Saturn also radiates twice as much energy as it receives from the Sun -- this energy probably comes from differentiation (helium rain) - Neptune also emits nearly twice as much energy as it receives, but the source of that energy remains a mystery
How did interior cooling of Mars kill it?
- Since Mars is among the smallest planets in the solar system, it cooled very quickly and when it cooled, it lost its magnetic fields (that protect the atmosphere from the damaging effects of the solar winds -- as well as the harmful ultraviolet and gamma rays from the sun that would kill humans) and thus it lost most of its atmosphere. There is still a very thin, barely noticeable layer of atmosphere on Mars, but it is slowing being stripped away by the solar winds because there is no conduction in the interior to create magnetic fields to protect the little atmosphere that it does have - the cooling of the interior of Mars also meant that volcanic activity died down and was therefore unable to release gases into the atmosphere to replenish it.
Why are small Jovian moons different from Medium and Large Jovian moons?
- Small Jovian moons are far more numerous than the medium and large moons - they do not have enough self-gravity to be spherical: most are "potato-shaped" - They are captured asteroids or comets, so their orbits DO NOT follow usual patterns of planets and large moons (i.e. not circular or uniform to other planets)
What is the status of geological activity across the three main types of Jovian moons?
- Small Moons: no geological activity - Medium-sized Moons: geological activity in the past - Large Moons: ongoing geological activity
Why can't we always see molecular clouds?
- Solar dust can sometimes block our view of molecular clouds -- we can see through the dust using infrared vision
What are solar flares? What causes them?
- Solar flares are caused by magnetic activity that sends bursts of X-rays and charged particles into space
In general, how do stars form?
- Stars form in massive, dense, cold molecular clouds where gravity is strong enough to overcome thermal pressure - such a cloud contracts and clumps, getting denser and hotter as it contracts and as gravitational potential energy is converted to thermal energy - becomes a protostar, with energy provided by the slowed down contraction
What is the Corona of the Sun? How hot is it?
- The corona is the outermost layer of the solar atmosphere - Temperatures are around 1 million K - very weak layer of the Sun - The corona cannot be seen in visible light except by eclipsing the Sun (meaning blocking out the light emitting core of the Sun)
what is a solar prominence?
- a solar prominence is a large, bright feature extending outward from the Sun's surface - do not confuse this with the bright loops of gas that connect sunspots. Solar prominences look like worms sticking out of the Sun.
How, exactly, does a comet tail / jet stream form?
- Stars out far from the Sun looking like a normal comet - As it approaches 5 AU in its elliptical orbit, the nucleus warms and begins to sublimate - gas coma begins to form around the nucleus when the comet is about 5 AU from the Sun - The tail forms when the nucleus is about 1 AU from the Sun -- the tail points away from the Sun at all points during this process / "orbit" around the Sun - Dust tail is pushed up by the sunlight while the plasma tail is swept back by solar wind. so that it separates from the dust tail -- largerparticles are unaffected by sunlight or solar wind - solar heating diminishes as the nucleus moves further from the Sun; coma of gas and tail disappear as the nucleus moves out to 3 and 5 AU from the Sun
How does solar activity vary with time? What is an example?
- Sun spots, for example, rise and fall in an 11-year cycle. There are additional variances over longer periods
What are Sun Spots? How hot are they?
- Sunspots are cooler than other parts of the Sun's surface - Sunspots are around 4,000 K compared to the 6,000K temperature of the surface of the Sun - Sun spots are regions with strong magnetic fields
Why is Io the most volcanically active body in the solar system?
- TIDAL HEATING
How can temperature be determined?
- Temperature can be determined from color and spectral type, though spectral type is a much more reliable method
why haven't any exoplanets been detected by the Astrometric Method?
- The Astrometric Method aims at measuring the change in a star's position in the sky - However, these tiny motions are very difficult to measure (about 0.001 arcseconds distance of change)
what happens in the Convection Zone of the Sun?
- The Convection Zone is a more efficient way to transport energy than radiation in the radiation zone - Conditions in the convection zone are just right for convection (rising hot parcels of gas and sinking of cooler parcels of gas) to transport energy more efficiently and more quickly than radiation in the radiation zone - Rising of hot plasma carries energy through the convection zone to the photosphere
what else, besides the existence of an exoplanet, can the Doppler Method tell us?
- The Doppler Method can tell us about an exoplanet's mass, distance from its star (via its period), and shape of its orbit
In what ways is the Doppler method biased?
- The Doppler method favors detection of exoplanets that are: 1. Massive (accelerate star more) 2. Closer to a star (accelerates star more)
Why are there more impact craters on Mars than there are on Earth?
- The Earth's atmosphere and continuous volcanic activity has allowed for the weathering down of craters while resurfacing has erased many craters and given new surfaces
What is the Moon's atmosphere like? What are the temperatures like?
- The Moon has no atmosphere and thus the temperatures on both ends are very extreme
How big is the radius of the Sun compared to the size of the Earth?
- The Sun has a radius that is about 100 times the radius of the Earth
How much more massive is the Sun than the Earth?
- The Sun is about 300,000 times more massive than the Earth
How is the Sun able to keep the Sun shining at such high luminosity for so long? Where does it get all of this energy?
- The Sun is fueled by Nuclear Energy
What must fuse in order for the Sun to release energy?
- The Sun releases energy by fusing 4 H nuclei into 1 He nucleus
How hot is the Sun's surface and core?
- The Sun's surface is about 6,000 K - The Sun's core is about 15,000,000 K
what else, besides the existence of a an exoplanet, can the Transmit Method tell us about exoplanets?
- The Transmit Method reveals distance from the star (via the period) and size (diameter) of the exoplanet
What is the relationship between apparent brightness and distance?
- The apparent brightness decreases as inverse square of the distance from the source -- the more distance increases, the more the apparent brightness decreases
what is the Chromosphere of the Sun? How hot is it? Why is it hotter than the Photosphere?
- The chromosphere is the middle layer of the solar atmosphere - the chromosphere's temperatures are about 100,000 to 1 million K - the chromosphere is what you would see in an eclipse when the light emitting core of the Sun is blocked out by there is still a thin circle of light around the outer edges of the transisting moon, that is the chromosphere. - The chromosphere is actually hotter than the photosphere, even though the photosphere is on the actual Sun - This is because lighter gases in the chromosphere burn where they wouldn't in the photosphere. - Magnetic energy from the Sun's magnetic fields acts out in the Chromosphere, not in the Photosphere: think of a whip, the whip lashes out and has the most impact at the end, therefore the most energy at the end, furthest from the handle
what is the color and surface temperature of the coolest stars?
- The coolest stars are red and have surface temperatures of around 3,000 K
What happens in the core of the Sun?
- The core is where the nuclear fusion occurs that supplies the Sun with the nuclear potential energy that has kept it luminous and hot for around 10 billion years - it is around 15 million K - Density is 10 times more than that of lead - Hot and dense enough for nuclear fusion - Source of energy for the Sun
What is the Solar Thermostat? How does it work?
- The solar thermostat explains why the Sun is stable and not explosive like a bomb - a decline in core temperature causes the fusion rate to drop (cooler temperature means less atom activity and slow speeds, which means less ability to get over that electromagnetic repulsion hump and fuse with another nuclei), so the core contracts and heats up (things that contract heat up -- cotton ball), which increases the fusion rate again - there is a decline in core temperature only because of core contraction that heats up the core, increasing the fusion rate, and expanding the core (when things heat up, they expand), when it expands, it cools, slowing down the fusion rate, which in turn causes the core to contract again and heat up again and so on - this is a cyclic pattern and keeps going so that the Sun will never cool down or never heat up and explode, i.e. it is stable
What did the 2005 UMD-led mission to a comet do?
- The spacecraft released a 400 kg "impactor" that traveled at 10 km/s and hit the comet - There was an explosion, where kinetic energy thermalized into heat, blasting a crater in the comet - the impactor removed some of the surface layers, and revealed a primordial material from the birth of the solar system
Why can't fire be a reasonable explanation for the source of the Sun's energy?
- The sun is so luminous that its chemical energy would be used up in just 10,000 years
Generally, how do exoplanets compare with planets in our own solar system?
- There are exoplanets with a wide variety of masses and sizes and densities - many of these exoplanets are orbiting close to their stars and with large masses
What else do we know about Ganymede in terms of heating and geological activity
- There is clear evidence of geological activity - There is clear evidence of tidal heating - Possibly heat from radioactive decay
What do sunspots, solar flares, solar prominences, sand coronal mass ejections have in common?
- They are all considered solar activity and are all phenomena that are related to magnetic fields
How do the Jovian planets affect impacts of meteorites on Earth?
- They can influence smaller bodies through their gravity because of their large masses - a Jovian planet can "nudge" an asteroid in the Asteroid Belt, sending it towards Earth and other planets - the gravity of a Jovian planet (especially Jupiter) can redirect a comet into the inner solar system - Jupiter has directed some comets toward Earth in the past, but has ejected many more into the Oort Cloud
What happens to stars that are less massive than .08 times the mass of the Sun?
- They cannot sustain fusion, and so they cool off and quickly become dim
in terms of geological activity, what are the medium moons of Uranus like>
- They have varying amounts of geological activity
What is an Absorption Line Spectrum? How is it characterized? What is one example?
- Think if you are absorbing something, you are taking it in, i.e. the graph has dips Example - a cold cloud of gas between us and a light bulb can ABSORB light of specific wavelengths, leaving dark absorption lines in the spectrum. By observing what wavelengths are absorbed, we can deduce the composition of the absorber
Why don't oxygen and nitrogen, the bulk of the atmosphere, contribute to the greenhouse effect?
- Though oxygen and nitrogen comprise the bulk of the atmosphere, they do not absorb in the infrared so they do not contribute to the greenhouse effect
So generally, how does the energy from fusion get out of the Sun?
- Through the radiation zone and the convection zone - But, the radiation zone is so massive and opaque that it can take up to a million years for photons to escape - The convection zone is a more efficient way for photons to escape through convection cells
Why are Jupiter's Moons so geologically active?
- Tidal heating drives geological activity, and ice melts at lower temperatures than rock, leading to Io's volcanoes and to icy geological activity on the other moons
What is Titan?
- Titan is the largest moon of Saturn
What is unique about Titan?
- Titan is the only moon in the solar system to have a thick atmosphere
what is the composition of Titan's atmosphere?
- Titan's atmosphere consists of mostly nitrogen, with some argon, methane, and ethane
what is needed to have strong magnetic fields?
- To have a strong magnetic field, a planet must be geologically active, with a hot, conductive, molten iron core, AND rotating - Mercury, the Moon, and Mars are not geologically active enough (because their cores have cooled off) and thus they cannot have a magnetic field to shield their atmospheres (or hat is left of them) from the destructive solar winds - Venus is not rotating fast enough for it to have a protective magnetic field.
How can changes in a star's brightness reveal the presence of exoplanets?
- Transit Method - for the small percentage of solar systems where we happen to be in the plane of system, the planet can "transit" in front of its star and block some of the star's light that we see - Before transit, the star has its full visible light brightness - during transit, the planet blocks some of the star's visible light - before eclipse, the system's infrared brightness comes from both the star and the planet - During an eclipse (i.e. when the planet goes behind the star), the star blocks the planet's infrared distribution (small shallow dip -- just taking away the system's infrared brightness coming from the planet, still have it from the star, hence why the dip is not as large -- in other words the brightness we is a result of both the planet and the star, when the planet is eclipsed, we don't lose as much light (don't have such a large dip) as when we have a transit and the planet moves in front of the star
Which is more commonly used, the Transmit Method or the Doppler Method?
- Transit Method, though the Doppler method has been used to detect many exoplanets
What is Triton?
- Triton is the largest moon of Neptune - Triton is likely a captured Kuiper Belt object -- makes sense because Neptune is the last and furthest planet out in the solar system and thus the one closest to the Kuiper belt, where a lot of comets are.
Why does a star leave the main sequence?
- a star leaves the main sequence once it has finished fusing H to He in its core
Why is the lack of rain so detrimental to a planet's greenhouse effect, like Venus?
- Venus is too close to the Sun for there to be rain. - rain is simply the byproduct of the ability of water to condensate (which requires cooler temperatures). On earth, rain is what constantly removes CO2 from the Earth's atmosphere. Yet since it is too hot on Venus (because it is so close to the Sun), for H2O to condensate and form rain, there is no natural way for all of that CO2 in Venus' atmosphere to be removed. - Thus, over time, the more CO2 that builds up in Venus' atmosphere, the thicker the atmosphere became because there was nothing to remove it. Add another greenhouse gas to the mix (evaporated water), and you have a massive greenhouse effect that made Venus so hot that eventually all of the primordial water (water that was originally brought over, perhaps from a comet,) evaporated into the atmosphere until there was none left
without the greenhouse effect, how different would the temperatures on Venus, Earth, and Mars be?
- Venus would be 510 C colder without its intense greenhouse effect - Earth would be 30 C colder without its moderate greenhouse effect - Mars would be 6 C colder - All would have an average temperature below freezing -- Earth would be -6 C (3 F) -- thus, some greenhouse effect is essential for life
What is the photosphere of the Sun? How thick is it? How hot is it?
- Very think layer above the convection zone - this is what we see from earth - It is about 5,000 km thick, which is very thin and so from 1 AU away, it looks like a sharp edge of surface - Temperature is around 6,000 K (surface temperature)
name the layers of Uranus and Neptune, going in order from surface to core
- Visible clouds - gaseous hydrogen - core: rock and metals, hydrogen compounds
Name the layers of Jupiter and Saturn, going in order from surface to core
- Visible clouds - gaseous hydrogen - liquid hydrogen - metallic hydrogen (which is still hydrogen, but because of all the added mass and compression for being so massive, it has been compressed so tightly that it is like a solid, metallic material) - core or rock, metals, and hydrogen compounds
What do volcanoes do that gives us our atmosphere? What are two ways this happens?
- Volcanoes vent gases, which gives us out atmosphere 1. Sudden eruption, like Mr. Saint Helens 2. Volcanic vents with pockets of gas coming out of the Earth is an example of more gradual outgassing
Through direct detection of exoplanets, specifically through photos and radar images, how can we tell if a star is young or not?
- We can tell if a star is really young or not based on how bright it shows up on the monitor. If a star is relatively young, it will still have its heat from when it was first formed, thus it will be glowing brighter in the infrared
what is the difference between a transit and an eclipse
- a Transit is when a planet crosses in front of a star, resulting in a large dip in brightness - an Eclipse is also sometimes seen, when the planet passes behind the star, resulting in a smaller dip in brightness -
What happens in nuclear FISSION? What are some examples?
- a big nucleus is split into smaller pieces - examples: uranium or plutonium nuclear power plants split the nucleus of an atom to create nuclear power
What is a binary system?
- a binary system is where two stars orbit around a mutual center of mass and thus share the same system
what happens to a brown dwarf over time?
- a brown dwarf's luminosity gradually declines with time as it loses thermal energy
What does a change in spectrum tell us?
- a change in spectrum, during a transit, tells us about the composition of a planet's atmosphere
What exactly is a protostar
- a contracting mass of gas that represents an early stage in the formation of a star - it looks like a nebula disk
What does a decrease in infrared radiation tell us?
- a decrease in infrared radiation when a planet is eclipsed by its star (when the planet goes behind the star) tells us the temperature of the planet - in other words, the amount of infrared radiation from the planet, that is now blocked by the eclipsing star, tells us how much infrared light the planet is able to emit
How can the Transmit Method tell us the size of an exoplanet?
- a large planet blocks out more of the star light and a smaller planet blocks out less of the star light - the percent of the star light, given on the y-axis, that is blocked, tells us the area (size) of the exoplanet
how can we use eclipsing binaries to infer the masses of each star in a binary star system?
- a larger dip coming after a small dip means that one of the stars is bigger than the other
When does a Protostar become a main-sequence star?
- a protostar becomes a main-sequence star when the core of the star becomes hot enough to start fusion - slow contraction continues until the core becomes hot enough for nuclear fusion, so that contraction is no longer needed to provide luminosity - Contraction stops when the energy released by the core fusion balances out energy radiated from the surface
What happens in nuclear FUSION? What are some examples?
- a small nuclei sticks to another small nuclei to, together, make a bigger one - Examples: the Sun, stars -- still trying to develop this on Earth for power. This would give us the ability to create our own energy source instead of burning fossil fuels and creating massive carbon emission rates
Transit and Doppler Methods have strong biases against detecting planets beyond...
1 AU
what are the 2 reasons that explain why it is so hard to detect exoplanets?
1. A Sun-like star, for example, is about a billion times brighter than the light reflected from its planets. In other words, the star is so bright that from a distance, it is hard to see the planets around it because the light from the star overpowers the light from the surrounding planets 2. Stars are so far away, and at those great distances, planets appear extremely close to their stars and are very hard to see (again, because the stars are so bright compared to the planets)
What are 2 tools that are used to separate light into its component wavelengths?
1. A glass prism 2. Diffraction grating
What are 3 methods of INDIRECT detection of exoplanets?
1. Astrometric Method 2. Doppler Method 3. Transit Method
What are the primary greenhouse gases?
1. Carbon dioxide 2. Water vapor
What are the 3 basic types of spectra?
1. Continuous Spectrum 2. Emission Line Spectrum 3. Absorption Line Spectrum
What 3 components do all Terrestrial planets have in common in their interiors?
1. Core 2. Mantle 3. Crust
What are the four main kinds of erosion and how does it help to wear away impact craters?
1. Flowing Water - the Colorado River has been carving the Grand Canyon for millions of years 2. Glaciers - Glaciers created Yosemite Valley during the ice ages 3. Wind - wind erosion wears away rocks and builds up sand dunes 4. River Delta - a river delta is built from sediments that were worn away by wind and rain and then carried downstream by water. The delta looks like an outgrowth of the shores because of the deposited sediments
What are the two reasons that explain why the the Sun stopped contracting and maintain its radius and luminosity for billions of years?
1. It came into a gravitational equilibrium 2. It's in Energy Balance
What are the two major factors that allow for earth to remain geologically active and have oceans?
1. Mass 2. Distance from the Sun
In summary, what are the 3 ways in which atmospheres affect conditions on earth?
1. erosion: wind, water 2. Protect the surface from harmful radiation (from the Sun) 3. warm the surface through a modest greenhouse effect
Review: What are the two main sources of INTERNAL heat?
1. gravitational potential energy converted to thermal energy as planets form -- most important source of heating at birth of planet 2. Radioactive decay -- most important source of heating for a planet today
What are the corresponding frequencies of the following impacts? 1. Small impacts 2. Large impacts
1. small impacts happen almost daily 2. impacts large enough to cause mass extinction happen many millions of years apart (around 100 million years apart)
What are the process that re-shape a terrestrial planet's surface?
1. smaller impacts after the period of heavy bombardment that partially covered the craters left over from the larger impacts of comets, meteorites, and asteroids during the period of heavy bombardment 2. large craters were worn down by micrometeorite impacts. This process is basically the same as "sandblasting" the impact craters, but occurs much less frequently, yet still happens over billions of years 3. Tectonics - recycling of planet surfaces 4. Volcanism - eruption of molten rock onto the surface, creating new surface that goes over the cratered surfaces 5. Erosion - surfaces changes caused by wind, water, or ice
What is the difference between an asteroid, a comet, and a dwarf planet?
Asteroids: are left-over inner solar system planetesimals Comets: are left-over outer solar system planetesimals Dwarf Planets: are either of these massive enough to be round and make spherical by gravity
How do we measure the mass of an exoplanet? a.) from the fraction of star light that is blocked in transit b.) using the Doppler Method to measure the variations in speed of its star c.) measuring the exoplanets orbital period and distance
B
Suppose a star is 100,000 AU from Earth. We measure its apparent brightness to be 10 billion times fainter than the sun's apparent brightness. How does the star's luminosity compare with that of the Sun's? a.) its luminosity is 1,000 times less b.) it has the same luminosity c.) its luminosity is 1,000 times greater d.) its luminosity is 10 billion times fainter
B
What would happen inside the Sun if a slight rise in core temperature led to a rapid rise in fusion energy? a.) the core would expand and heat up slightly b.) the core would expand and cool c.) the sun would blow up like a hydrogen bomb
B
Which of the following is NOT a reason most of the large and medium Jovian moons are more geologically active than Mercury? a.) Ice melts at lower temperatures than rock b.) the lower mass of moons compared to planets make escape from gravity easier c.) tidal heating by the Jovian moon heats the moon's interior
B
what would happen to earth's surface temperature if earth's atmosphere contained more carbon dioxide? a. it would go up b. it would go down c. it would not change
Correct Answer: A
Why can't our eyes see people in the dark? a. people do not emit any kinds of light b. people are too cool to emit visible light c. people are too small to emit enough light for us to see d. people do not contain enough radioactive material
Correct Answer: B. An object has to be hot enough to at least register in the red section of visible light. Think of the picture of the man with the garbage bag. In normal vision, we cannot see anything. This shows that yes, you do glow in the dark, but in the infrared, not in visible light -- the reason is the same logic as the coal poker and the fire -- we are not hot enough to register in visible light, but hot enough to register in the infrared
Earth and Venus have more geological activity than Mercury and Mars. This is because: a.) Earth is younger than Mars b.) Earth is closer to the Sun that Mars c.) Earth has more volcanic activity than Mars d.) Earth is more massive than Mars
Correct answer: D
What contributes to making Earth habitable? a.) it is massive enough to retain atmosphere and have geological activity b.) it is at the right distance from the Sun c.) it does not (yet) have a runaway greenhouse effect d.) all of the above
D.
what are the shortest and most powerful wavelengths on the electromagnetic spectrum?
Gamma rays. Gamma rays are the shortest, most hard hitting, impactful and destructive wavelengths
Review: what is the difference between Gravitational equilibrium and energy balance?
Gravitational Equilibrium - energy supplied by hydrogen fusion in the core counter-balances the pressure from the inward crush of gravity Energy Balance - the rate at which energy is radiated from the surface of the Sun is equal to the rate at which it is released by fusion in the core
What is the Runaway Greenhouse effect?
If earth moved into venus' orbit close to the Sun... - there would be more intense sunlight that would raise the surface temperature on earth by about 30 C - higher temperatures would increase evaporation, and warmer air holds more water vapor (one of two main greenhouse gases). This additional water vapor would further strengthen the greenhouse effect - result: all the oceans would evaporate and carbonate rocks would decompose, releasing CO2 into the atmosphere and making Earth hotter than Venus - Eventually, atmospheric H2O would be broken down into H and O by solar radiation, and H would escape into space or would be carried away by solar winds (because it is the lightest gas / element in the universe), so Venus will never have much water ever again, if any
what/where are the two places that an atmosphere can lose it gasses? how does it happen?
In the air: - as temperature increases, molecular activity of gas particles increases as well - thermal escape occurs when atoms or molecules get fast enough to eventually achieve escape velocity that is greater than that of the planet's - the solar wind can sweep these now loose particles into space - these loss processes are permanent On the ground: - condensation returns gas to the surface as rain, snow, or frost - chemical reactions can incorporate gas into surface materials - these loss processes could be reversed
- What is the formula for calculating the period or mass of a binary system?
Newton's form of Kepler's 3rd Law! p^2 = 4(pi)^2 / G(M1+M2)^a^3 where p = period, and a = average SEPARATION
what are the longest and least powerful wavelengths on the electromagnetic spectrum?
Radio waves. radio waves are the longest, least destructive, most spread out wavelengths
How does mass allow for earth to remain geologically active and have oceans?
Small terrestrial planets: - interiors have cooled off - cold, solid interiors - tectonic and volcanic activity ends rather quickly - little outgassing, atmosphere lost due to low gravity, low escape speed, lack of replenishment from volcanic outgassing, loss of magnetic fields due to no conductive, hot core - no atmosphere, therefore no erosion Large terrestrial planets - warm, convecting interior - ongoing tectonic and volcanic activity - most ancient craters have been erased because of weathering and volcanic activity - lots of outgassing - strong gravity, high escape speeds, retains atmosphere -- magnetic fields still protect atmosphere, erosion possible In short, a planet needs to be massive enough to still have the geological activity needed for volcanoes to vent water and carbon dioxide into the atmosphere. Presence of magnetic fields and escape speeds also depend on planet mass
what is the formula for the speed of light?
Speed of Light = wavelength x frequency
Does Venus have lava?
Yes. Venus evidently has lava flow and weathering
