Ast 101 Test 2
Consider the four stars shown following. Rank the stars based on their surface temperature from highest to lowest.
(Highest Temperature) a blue white dwarf star Sun an orange main-sequence star a red supergiant star (Lowest Temperature) (Notice that temperature is related to color, and follows the order of the colors in the rainbow: Blue (or violet) stars are the hottest, while red stars are the coolest.)
The full Moon's apparent magnitude is
-12.5.
Stellar masses are measured directly by observations of the motions of
-eclipsing binary systems. -spectroscopic binary systems. -visual binary systems. All of the above can give us their masses.
What is required to maintain the narrow rings seen around Saturn, Uranus, and Neptune?
A pair of shepherd satellites
What is a reasonable description of the Great Red Spot?
A very large hurricane
Jupiter's bright zones are cloud streams made of _____ ice crystals.
Ammonia
What is a planetary nebula?
An expanding shell of gas around a white dwarf star
The surface of Europa is most like the Earth's
Arctic Ocean.
Some jovian storms such as Jupiter's Great Red Spot have been observed to last for years to decades. The reason why these large storms live so long is not well understood, but astronomers have begun to monitor these storms more closely with spacecraft and have discovered some common properties among them. Which of the following properties does not contribute to the longevity of large jovian storms?
Atmosphere composed mainly of hydrogen and helium
Why does star formation require a "triggering" event?
Atoms are too small and far apart for gravity to overrule their individual motions and bring them together.
Which of these stars would be the hottest?
B0
The following figure shows how four identical stars appear in the night sky as seen from earth. The shading is used to indicate how bright (white) or dim (dark gray) the star would appear in the sky from Earth.
Brightest is closest, dimmest (or darkest) is most distant
Listed following are several fictitious stars with their luminosities given in terms of the Sun's luminosity (LSunLSun) and their distances from Earth given in light-years (lyly). Rank the stars based on how bright each would appear in the sky as seen from Earth, from brightest to dimmest. If two (or more) stars have the same brightness in the sky, show this equality by dragging one star on top of the other(s).
Brightest: Nismo, then (overlapping because they're the same) Shelby and Ferdinand, then Enzo, then Lotus (dimmest)
Which of the following is NOT an intrinsic property of a star?
Distance
The following images show Earth and the four jovian planets of our solar system. Rank these planets from left to right based on their mass, from lowest to highest. (Not to scale.)
Earth Uranus Neptune Saturn Jupiter
Jupiter has a relatively fast rotation rate, which serves to maintain stable wind patterns. The alternating westward and eastward band patterns are known as zonal flow. The following figure illustrates the zonal flow pattern through the graph. Label the graph with the appropriate descriptions.
Equatorial Belt ------------------Low Velocity Region Equitorial Zone------------Large positive velocity region Largest Negative Velocity Peak---Largest Pos. vel. peak
Which of these moons are most interesting to exobiologists?
Europa and Titan
What is the gravitational force exerted on Uranus by Neptune, at closest approach?
FUranus−NepruneFUranus−Neprune = 2.8×10^17N
All nine planets in the solar system have been visited by spacecraft.
False
Emission nebulae get their red color from the red supergiants forming in them.
False
Hydrogen fusion is the process in the Sun in which hydrogen atoms stick together to form carbon, releasing energy.
False
In high-resolution photographs, the surface of the Sun appears to be perfectly smooth.
False
Most of our detailed knowledge of the jovian planets comes from the Hubble Space Telescope.
False
Our Sun will eventually become a nova.
False
The Sun's radius is one astronomical unit by definition.
False
The composition of the Sun (see Table 9.2) is the same throughout the Sun.
False
The following figures show four stages that occur during the formation of a one-solar-mass star. Rank these stages based on their rotation rate, from fastest to slowest. (Assume that the angular momentum of the forming star is conserved throughout the formation process, though in fact it may shed some angular momentum by ejecting material into interstellar space.)
Fastest to slowest rotation: -main-sequence star -protostar with jets -contracting cloud trapping with infrared light -molecular-cloud fragment
During a "helium flash," which occurs during the red giant phase of a low-mass star:
Helium fuses into carbon in the star's core
Listed following are some of the distinguishing geological characteristics of the moons orbiting Jupiter. Match each characteristic to the appropriate moon.
Io- source of ionized gas in the donut-shaped charged particle belt around jupiter - hot, glowing lava visible in some photos- volcanoes currently erupting Europa - surface features provide evidence of a subsurface liquid ocean - ice covered surface with few impact craters Ganymede - largest moon in the solar system- heavily cratered terrain adjacent to much younger terrain
A massive star will collapse when iron is produced in the core because
Iron will not fuse, so the core doesn't produce energy to oppose the inward gravitational pull of the star
What happens to light passing through even thin clouds of dust?
It dims and reddens the light of all more distant stars.
What is true of Jupiter's magnetosphere?
It has a tail that extends at least to Saturn's orbit. Submit
The most massive planet in the solar system is
Jupiter
The following images show four planets in our solar system. Rank these planets from left to right based on the number of moons that orbit them, from highest to lowest. (Not to scale.)
Jupiter Mars Earth Mercury
What is the luminosity, in solar units, of a brown dwarf whose radius is 0.1 solar radius and whose surface temperature is 600
L =1×10−6 solar units
The following figures show the spectral types of four main-sequence stars. Rank them based on the time each takes, from longest to shortest, to go from a protostar to a main-sequence star during the formation process.
Longest to shortest time: -M6 -G2 -A5 -O9
the farthest major planet from the sun is
Neptune
Why does fusion only occur under conditions of extremely high temperature?
Protons normally repel each other, so only in a hot gas are they traveling fast enough to approach each other closely. -The threshold temperature in a star is about 10 million K for fusion to occur.
A star radiates light across the electromagnetic spectrum in what is known as a spectral intensity distribution. Because each star's surface has a characteristic temperature, the resulting spectral intensity distribution approximates that of an ideal blackbody. In the figure, the theoretical blackbody curves for three stars of differing surface temperatures are plotted. Here, the sizes of the idealized stars can be assumed to be equal. Sort the following observable stellar characteristics with the correct star.
Star A: 30,000 K: -the star appearing bluest -the star with maximum intensity at ultraviolet wavelengths -the star appearing brightest Star B: 10,000 K: -the star whose equal intensities measured through yellow (V) and blue (B) filters Star C: 3,000 K: -the star appearing reddestthe star with maximum intensity at infrared wavelengths
An astronomer measures the light coming from two stars, star A and star B. They appear to be equally bright. From other measurements, she knows that star B is actually twice as far away as star A. What can she conclude?
Star B is actually four times as bright as star A.
What happens to the surface temperature and radius of a star like the Sun as it goes from the main sequence to the red giant branch?
Temperature decreases, radius increases
What would happen if the fusion rate in the core of the Sun were increased but the core could not expand?
The Sun's core would start to heat up, and the rate of fusion would increase even more. Submit
What two forces are in balance inside the Sun?
The Sun's gravity inward and the force of gas pressure pushing outward.
A moon orbits a planet because of the gravitational force between them. Likewise, each body also experiences a tidal force due to gravity. Consider how the magnitude of the tidal force changes as the distance between a planet and moon varies.
The gravitational force on a moon is greater the closer it is to the planet. As the gravitational force increases, so does the tidal force exerted on a moon by the planet's gravity.
As a low-mass main-sequence star runs out of fuel in its core, it actually becomes brighter. How is this possible?
The outer layers expand due to the faster rate of fusion in a shell around the dead core.
Why do sunspots appear dark?
They have relatively lower temperatures than the brighter, background photosphere
The time between successive sunspot maxima is about
decade
The Sun will eventually become a supernova.
false
A visual binary star is a pair of stars that have been demonstrated to be gravitationally linked.
true
Of all forms of electromagnetic energy, _____ radiation gives us the least access to our entire Milky Way Galaxy.
visible light
While the mantless of Jupiter and Saturn are made of liquid metallic hydrogen, the mantles of Uranus and Neptune are chiefly
water
The maria on Ganymede were formed by
water erupting and spreading over the surface.
Saturn's cloud layers are much thicker than those of Jupiter because Saturn has
weaker surface gravity. Submit
When does a newly forming star have the greatest luminosity?
when it is a shrinking protostar with no internal fusion
A star like the Sun will end up as a
white dwarf.
Which of these events is not possible?
white dwarfs and companion stars producing recurrent Type I supernova events
If stars A and B are both main-sequence stars and star A has a greater fusion rate than star B, which of the following statements hold(s)?
-Star A must be more luminous than star B. -Star A must be more massive than star B.
After the discovery of Uranus, astronomers calculated its orbit and predicted its position in the sky using Kepler's laws of planetary motion, which had been known since the early 17th century. However, they soon discovered a small discrepancy between the predicted and actual positions of Uranus. As a scientist, what should you do when presented with such a conflict between prediction and observation?
-consider that uranus may not be a planet-verify that your observations are correct-think about what else might cause the observed discrepancy-consider whether Kepler's laws need to be modified to account for the new observations
Compared to the size of the Sun, stars of all types range from
0.01 to 1,000 solar radii.
In what range of masses are most stars found?
0.1 to 100 solar masses
How far away is the star Spica, whose parallax is 0.012"?
D=83 pc
We have seen that starlight passing through the interstellar medium is dimmed and reddened. Look at the photo of a sunset on Earth. The Sun's light also appears reddish at sunset. Given your understanding of the reddening of starlight, why do you think sunsets appear red?
Dust particles in the atmosphere scatter short wavelength blue light, leaving mostly red light to reach our eyes.
The following images show Earth and the four jovian planets of our solar system. Rank these planets from left to right based on their size (average equatorial radius), from smallest to largest. (Not to scale.)
Earth Neptune Uranus Saturn Jupiter
The following images show Earth and the four jovian planets of our solar system. Rank these planets from left to right based on their distance from the Sun, from closest to farthest. (Not to scale.)
Earth Jupiter Saturn Uranus Neptune
Most of the interior of Io is molten because of heat given off by the extremely high concentration of radioactive isotopes found in this moon.
False
Our Sun will fade in luminosity as its supply of hydrogen drops in a billion years.
False
Pluto has a size and density comparable to the Earth's Moon.
False
Solar mass stars eventually become hot enough for carbon nuclei to fuse together.
False
The Cassini division in the rings of Saturn is caused by tidal forces from Saturn.
False
The Earth's atmosphere extends much farther into space than does Titan's atmosphere, because the Earth is much larger than Titan.
False
The Sun is about the same temperature all the way through.
False
The following images show five planets in our solar system. Rank these planets from left to right based on their average surface (or cloud-top) temperature, from highest to lowest. (Not to scale.)
Highest temperature to Lowest temperature: Mercury Earth Mars Jupiter Neptune
Provided following are four different ranges of stellar masses. Rank the stellar mass ranges based on how many stars in each range you would expect to be born in a star cluster, from highest number to lowest number.
Highest to lowest number: -less than 1 solar mass -between 1 and 10 solar masses -between 10 and 30 solar masses -between 30 and 60 solar masses
Provided following are the spectral types of four different main-sequence stars. Rank the stars based on the strength of the radiation pressure that pushes outward as they are forming, from highest pressure to lowest pressure.
Highest to lowest radiation pressure: -O9 -A5 -G2 -M6
The following figures show four stages that occur during the formation of a one-solar-mass star. Rank these stages based on the central temperature, from highest to lowest.
Highest to lowest temp: -main-sequence star -protostar with jets -contracting cloud trapping infrared light -molecular-cloud fragment
What is the solar constant?
How much solar energy is received per square meter of area every second at Earth's distance from the Sun Submit
Which of the following methods is useful for determining a star's approximate surface temperature?
Measuring its apparent brightness through two or more color filters and comparing these values
What is the source of Io's volcanic activity?
Tidal heating
The only moon with a thick atmosphere is
Titan
Which of these moons has the densest atmosphere?
Titan
Pluto is most similar to
Triton
The erupting geysers of nitrogen gas on Triton
are caused by a not yet determined internal energy source.
A star (no matter what its mass) spends most of its life
as a main-sequence star.
Compared to Saturn, Jupiter is about
three times more massive and denser.
To find the _____ velocity, we must combine proper motion and parallax data.
transverse
Most of the stars in the galaxy are members of multiple-star systems.
true
Most stars are considerably smaller in radius and dimmer than the Sun.
true
Once a star's temperature and luminosity are determined, it is possible to determine the star's size.
true
Ordinary novae occur in binary-star systems.
true
Pluto is probably one of the largest of the Kuiper Belt bodies beyond Neptune.
true
Radio emission at 21-cm wavelength is due to neutral atomic hydrogen in interstellar regions.
true
Saturn's ring particles are made up mainly of water ice.
true
Saturn's rings have narrow gaps caused by small moonlets orbiting within the rings.
true
Starlight passing through a dusty region of space appears dimmer and redder.
true
Stars leave the main sequence only when they run out of hydrogen in their cores.
true
Supernovae leave behind nebulae that provide the raw material to make new stars. Our Sun and the Earth itself are formed from such recycled material.
true
The H-R diagram for a star cluster that was formed 10 billion years ago would have no main-sequence stars with masses greater than the mass of the Sun.
true
The average density of interstellar matter is about 1 atom per cubic centimeter.
true
The central star of a planetary nebula is the exposed core of a red giant.
true
The composition of most emission nebulae, absorption nebulae, and dust clouds is primarily hydrogen and a smaller amount of helium gas.
true
The lighter mare on Ganymede was created by water that erupted from within the moon.
true
The number of neutrinos detected on Earth is substantially smaller than that predicted by the standard solar model.
true
Dark dust clouds are identified as individual objects because they occupy defined regions in the interstellar medium and have specific physical characteristics. Of the following statements, select those that correctly describe the physical characteristics of dark dust clouds.
- They comprise mainly gas with some dust. - They are cold. - They have a higher density than the interstellar medium.
All four jovian planets have storm systems in their atmospheres. From the list below, select the atmospheric characteristics that are found on all four jovian planets.
-Banded atmospheric patterns consisting of light colored zones and dark colored belts -Small oval-shaped storm systems -Rapid winds
As astronomers continued to study Pluto and objects in the Kuiper belt, it became clear that Pluto has more in common with Kuiper belt objects than with the eight major planets in the solar system. With the discovery of Eris, an object even larger than Pluto, the International Astronomical Union introduced a new category of solar system objects called dwarf planets. Pluto was reclassified as a dwarf planet in 2006. Which of the following factors contributed to the evolution of scientific thinking that led to the reclassification of Pluto as a dwarf planet?
-Better technology led to improved understanding of objects in the solar system -Terminology and classifications changed as scientific understanding and knowledge evolved -more precise observations provided new information about the nature of pluto
You should now have some appreciation for the utility of stellar spectra and the modern spectroscopic sequence as important tools for determining the temperatures of stellar atmospheres. Now it's time to combine what you have learned in Parts A and B by investigating how the colors, spectral classes, and stellar surface temperatures relate to one another. From hottest to coldest, the classification sequence is O, B, A, F, G, K, and M. The sequence can be remembered by the following mnemonic: Oh Be A Fine Girl (or Guy) Kiss Me! In the following figure, drag the appropriately colored star to the corresponding temperature and spectral class.
-Blue -Yellow -Orange -Red https://i.gyazo.com/84df0e39bd63975b70b60fc471ce5637.png
Starting with the hypothesis that a planet near Uranus was the cause of the orbital discrepancy, scientists had to develop a plan to find the unidentified planet. They started with what they knew about the discrepancies in the orbit of Uranus. Rank the steps in the order that scientists would take to discover the planet.
-First:Calculate the mass, orbit, and likely position of theunidentified planet. -Use optical telescope tosearch a region of the skywhere the unidentifiedplanet is predicted to be. -Compare current observationsto existing star charts to locateany new objects -Make continued observationsto determine if the new objectchanges position relative to background stars.
Jupiter's differential rotation and complex atmospheric structure induce turbulent storms, such as the Great Red Spot. Identify the statements that correctly describe the characteristics of storm systems on Jupiter.
-On Jupiter, the larger the storm, the longer it can last. -Individual storm systems can interact, resulting in the storm growing or fading out. -Storms are localized features, confined and powered by zonal flow.
Since the early 1990s, observations of the solar system beyond Neptune, where Pluto resides, have revealed numerous objects orbiting the Sun. This collection of objects is known as the Kuiper belt. More Kuiper belt objects are being discovered each year, providing astronomers with a better understanding of their physical and orbital properties. From the list below, identify which properties are characteristic of Kuiper belt objects.
-about 25% of Kuiper belt objects have the same orbital period as Pluto -Kuiper belt objects have a low relative brightness when observed from Earth -Kuiper belt objects orbit the Sun at great distances -Kuiper belt objects are small, icy bodies
Estimate the life expectancy of a 3-solar mass, 30-solar luminosity star.
1 billion years
What is the main-sequence (hydrogen core-burning) lifetime for stars like the Sun?
10 billion years Submit
What is the typical age for a globular cluster associated with our Milky Way?
10-12 billion years
What temperature is needed to fuse helium into carbon?
100 million K
Determine the wavelength corresponding to the peak of the black-body curve in the solar convection zone (105^5 K). What form does the radiation take?
10^5K = 29nmUltraviolet Far UV
Roughly how many wavelengths are needed to circle the Sun?
1500 N
In Figure 8.11 (Titan's Atmosphere) in the textbook, the atmospheric temperature at the top of the main haze layer is approximately
150k
To how many orbits does this correspond?
2.7orbits
A star has a parallax of .05." Its distance is
20 parsecs
Given that the Sun's lifetime is about 10 billion years, estimate the life expectancy of a 0.2-solar mass, 0.010-solar luminosity red dwarf.
200 billion years
A maximum in solar activity should next occur about
2023.
The _____-year solar cycle is characterized by a variation in the number of sunspots through a reversal of the magnetic polarity of the Sun as a whole.
22
How far does such a wave move during one wave period?
3000 km
How long does it take for the Sun to convert one Earth mass of hydrogen into helium?
320,000 years
What is the surface temperature of the Sun?
5780 Kelvin
The temperature of the photosphere is about
5800 kelvin
Interstellar gas is composed mainly of
90% hydrogen, 9% helium by weight.
The surface of Saturn's moon Iapetus shows which of the following features?
A light and a dark hemisphere Submit
A nova produces a characteristic light curve, which provides astronomers with details about the nova event. Select the appropriate light curve that shows how a nova's brightness changes over time.
A light curve of a nova event shows a sudden increase in luminosity in a matter of days, followed by a gradual fade over several months, until the white dwarf's luminosity returns to normal. (big uneven middle hump going up an down)
Jupiter's moon Europa might harbor life because it has which of the following conditions?
A liquid water subsurface layer
Which of the following changes would cause the fusion rate in the Sun's core to increase?
An increase in the core temperature and A decrease in the core radius.
As the distance of a star doubles, what happens to its apparent brightness?
Apparent brightness is one-quarter of its previous value.
Jupiter's band structure is composed of contrasting regions known as belts and zones. On the diagram, label the belt and zone regions and their corresponding directions of convection.
Belts - Zones Cold Air - Warm Air
Listed following is the same set of fictitious stars given in Part A. Rank the stars based on how bright each would appear in the sky as seen from Jupiter, from brightest to dimmest.
Brightest: Nismo, then (overlapping because they're the same) Shelby and Ferdinand, then Enzo, then Lotus (dimmest)
How do we typically determine the radius of a star?
Calculation of radius after determining temperature and luminosity.
Place, in order from the center outwards, the regions of the Sun
Core, Radiation Zone, Convection Zone, Photosphere- This order also traces how energy is transported from the core to the surface.
The appearance of dark dust clouds can be attributed to their interaction with radiation. Sort the following statements, concerning how dark dust clouds interact with radiation, as either correct or incorrect.
Correct: -Obscures visible light -Radiates infrared -Radiates radio waves Incorrect: -Transparent to visible light -Radiates visible light -Radiates ultraviolet
The standard solar model is a mathematical model that uses observational data and theoretical insights to describe the inner workings of the Sun. Two key parameters used in the standard solar model are temperature and density. If we assume that the Sun is in hydrostatic equilibrium, the model predicts that the Sun's temperature should ______ and its density should ______ from its core to its surface
Decrease, Decrease
The Great Dark Spot of Neptune is probably just as long-lived as the more famed Great Red Spot of Jupiter; both lie at about the same latitudes, and are about the same size, relative to their planet.
False
The Sun's innermost region is called its convection zone.
False
The average intensity of solar energy at the radius of Earth's orbit is about 1 watt per square meter.
False
The full cycle of Solar activity takes about 11 years to complete.
False
The helium flash increases the star's luminosity.
False
The less internal heat a jovian planet emits, the more it stirs up its clouds.
False
The main reason that stars evolved off the main sequence is because they are becoming less massive as energy is lost into space from the proton-proton cycle.
False
The most common chemical components of the Sun are hydrogen, helium, ammonia, and methane—just like Jupiter.
False
Triton at Neptune has a thick atmosphere similar to that of Titan at Saturn.
False
Triton at Neptune shows evidence of active geysers of liquid water.
False
Triton is increasing in the distance of its orbit around Neptune and will eventually escape.
False
Two stars have the same absolute magnitude, but one lies twice as far from Earth as the other. It will appear half as bright.
False
When two sunspots appear close together to form a spot pair, the two spots have the same magnetic field polarity.
False
In a binary-star system that produces a nova, the white dwarf pulls matter from the companion star. The matter forms an accretion disk that orbits the white dwarf. Then a specific sequence of events must take place for a nova event to occur.
First a) Material accumulates onto the white dwarf's surface, increasing in temperature and density. c) At a temperature of 10 million K, the accumulated surface hydrogen begins nuclear fusion. b) Nuclear fusion reactions cause an enormous but temporary increase in luminosity. d) As nuclear fuel is burned up or blown into space, fusion ceases and the star dims. Last (Once nuclear fusion starts for the material on the surface, it proceeds at a furious rate. The white dwarf flares up, then fades away as some of the nuclear fuel is exhausted. The rest of it is blown into space. Neither the companion nor the white dwarf is destroyed in the nova process, so once fusion ceases, they return to their original states and repeat the process. Astronomers have observed many such scenarios, called recurrent novae.)
The following figures show four stages that occur during the formation of a one-solar-mass star. Rank these stages based on the order in which they occur, from first to last.
First to last to occur: -molecular-cloud fragment -contracting cloud trapping infrared light -protostar with jets -main-sequence star
No nuclear reactions occur in the interior of a white dwarf. Its brilliance comes from stored heat. Therefore, the fate of an isolated white dwarf is to slowly lose its stored energy and dim over a long period of time. However, if a white dwarf is a member of a binary-star system with specific properties, the white dwarf can become explosively active. Label the components of such a binary-star system capable of producing a nova event.
For a white dwarf to become explosively active, the distance between the dwarf and the companion must be small enough that the white dwarf's gravitational field can pull matter away from the surface of the companion. Due to the rotation of the binary system, the matter flowing through the mass-transfer stream from the companion star forms a flattened disk, called an accretion disk, which orbits around the white dwarf. Main Sequence or giant star ----------------white dward mass transfer stream------------------------accretion disk
What eventually stops the collapse of the core of a very high-mass star?
Fusion of iron into even heavier elements in the core.
Gas and dust are the primary components of the interstellar medium. They differ in structural form, elemental composition, and the density with which each is distributed across the interstellar medium. Complete the table by placing the physical descriptions of gas and dust in the appropriate column.
Gas: Structural Forms - Atoms and small molecules Elemental Composition - Composed mainly of hydrogen and helium Density- Low density Dust: Structural Forms - Clumps of atoms and large molecules Elemental Composition - Composition varies Density - Extremely low density
Following are the four fundamental forces. Rank these forces from left to right based on their relative strengths between two protons located within the nucleus of an atom, from weakest to strongest.
Gravity; weak; electromagnetism; strong
Listed following are characteristics that describe either high-mass or low-mass stars. Match these characteristics to the appropriate category.
High Mass Stars: -late in life fuse carbon into heavier elements -end life as a supernova -have higher fusion rate during main sequence life Low Mass Stars: -the Sun is an example -have longer lifetimes -end life as a planetary nebula -final corpse is a white dwarf
In Part A, you considered the spectral intensity distributions emitted by stars of differing surface temperatures. The stellar spectra, when examined in greater detail, contain a wealth of information that can be used to describe various physical properties of the star (see figure). Most stellar spectra contain absorption lines that are produced by certain atoms and molecules in the stellar atmospheres, such as helium, hydrogen, heavy elements, and molecules. The width of a spectral line indicates the relative prominence of a given atom or molecule. A thin line is a "weak" line, meaning a relatively small presence, and a thick line is a "strong" line, meaning a relatively big presence.
Hot stars (temperatures exceeding 25,000K): -the bluest colors -very few lines of hydrogen and helium Intermediate-temperature stars (temperatures between 6,000K and 10,000K): -strong hydrogen lines -metal lines but no molecular lines Cool Stars (temperatures below 4,000K): -lots of metals and molecular lines -the reddest colors
Place the evolutionary stages of low-mass stars in order from earliest to latest in the star's life:
Hydrogen-> helium burning in core Red giant Planetary nebula Cooling white dwarf
The medium-sized Jovian moons are mostly made of what materials?
Ice and rock
Which of the following must occur for a star's core to reach equilibrium after an initial change in fusion rate?
If the fusion rate initially increases, then the core expands.If the fusion rate initially decreases, then the core contracts.
Rank the following steps that lead to a Type II supernova event in order of when they occur from first to last.
Initial State - Fusion Ceases - Photodisintegration of Core Atoms - Neutronization Begins - Core Rebound - Neutron Core Final State
Rank the following steps that lead to a Type I supernova event in order of when they occur from first to last.
Initial State -accretion disk on growing WD -WD at Chandrasekhar limit -carbon fusion begins -detonation Final State
Which are the four Galilean moons of Jupiter?
Io, Europa, Ganymede, and Callisto
What is so unusual about Pluto's orbit?
It is more inclined to the ecliptic than any of the eight planets.
You observe a low-mass helium white dwarf. What can you conclude?
It is part of a binary star system.
Evidence that Triton probably did not form around Neptune is
It orbits around Neptune in retrograde (backwards), opposite to the rotation of Neptune.
Why does a star like the Sun leave the main sequence?
It runs out of hydrogen fuel for nuclear fusion in its core.
Which of these is true about the seasons of Uranus?
Its strange tilt produces extreme seasonal variations, especially at the poles.
Watch the red dot representing the protostar in the video. After it reaches its highest point on the diagram, how do the protostar's surface temperature and luminosity change as it approaches the main sequence?
Its surface temperature increases, but its luminosity decreases.
Which of the following statements is NOT true about Saturn's moon Titan?
Its surface temperature is about the same as that of Earth.
Astronomers have detected storms in the atmospheres of the jovian planets, including giant storms that are larger than the entire planet Earth. Listed below are characteristics of storms. Sort these characteristics according to whether they are associated with jovian storms only, terrestrial storms only, or both jovian and terrestrial storms.
Jovian storms only -Associated with oppositely directed high speed atmosphereic flows and hosted by rapidly rotating plater Terrestrial Storms only - short lived and powered by solar radiation both - involve circulating winds and involved upwelling gasses
Of the two primary components of the interstellar medium, dust and gas, the interstellar gas does not obscure background light passing through to any great extent. Rather, the dark patches in the interstellar medium are caused by the effects of dust grains. Rank the dust grain sizes in the following hypothetical regions (A, B, and C) using the longest wavelength of light that each obscures as a measure of the grain size. Region A obscures all wavelengths of light shorter than ultraviolet light. Region B obscures all wavelengths of light shorter than visible light. Region C obscures all wavelengths of light shorter than infrared light. Rank from left to right the largest grains to smallest grains. To rank items as equivalent, overlap them.
Largest Grains - Dust in region C - Dust in region B - Dust in region A Smallest Grains
How do the properties of long-lived stars compare to those of short-lived stars?
Long-lived stars begin their lives with less mass and a smaller amount of hydrogen fuel. Long-lived stars are less luminous during their main-sequence lives.
From coolest to hottest, the seven letters for the star types are _____.
MKGFABO
Elements like oxygen, magnesium, and silicon are produced by
Massive stars only
Consider the orbiting system around Saturn. Within close proximity to Saturn are rings of material that are composed of hundreds of thousands of small particles. Outside of the rings is a multitude of orbiting moons, ranging in size from tens of kilometers in diameter to thousands of kilometers. Select the statements that correctly describe what would happen if a large moon passed inside of the Roche limit and what does happen to small clumps of material inside Saturn's rings.
Material inside the Roche limit will be restricted by tidal forces from forming into larger clumps or moons If a large moon passed inside of the Roche limit it would be torn apart by Saturn's large tidal forces.
The Sun's surface vibrates from internal pressure waves reflecting off of the photosphere and passing through the solar interior. Since these waves penetrate deep inside the Sun, an analysis of the vibrations these waves cause at the surface can reveal unique information about the solar interior. The science of studying the vibrations on the surface of the Sun is known as helioseismology. If you were a helioseismologist, which of the following observational methods could you use to obtain information about the solar interior?
Measure Doppler shifts in solar spectral lines & Determine the wavelengths and frequencies of individual pressure waves
Saturn's rings show signs of being an active and dynamic system, with many features changing on short timescales. Scientists believe that the rings are quite young. If the rings are indeed so young, then either they are the result of a relatively recent, possibly catastrophic event in the planet's system, or they are replenished from time to time. Select the statements that could explain how Saturn's rings were created or are replenished.
Medium-sized moons are torn apart as they pass into Saturn's Roche limit. Meteoritic impacts chip off debris from the moons just outside the Roche limit. A large comet collides with a moon near the Roche limit, breaking apart the moon. A collision occurs between two moons near the Roche limit, shattering both
Historically, the term nebula was used by astronomers to refer to any "fuzzy" patches seen in observations. They were described as "fuzzy" or hazy extended objects, in comparison to stars, which appear as points of light, and star clusters, which are extended groupings of many stars. A nebula can either be a light patch or a dark patch, depending on its internal characteristics and how it interacts with external radiation. Sort the following images as either a nebula or not a nebula.
Nebula: 2 pink photos that look likes clouds and 1 dark mass Not a nebula: 3 others Explanation: Nebulae can take on various appearances, depending on their physical shapes in space or the ways they interact with light. A nebula might take on interesting dark and light patterns depending on the presence of smaller emission and absorption features. The colors of nebulae are determined primarily by whether the light has been reflected by a nearby star, which makes the nebula appear bluish, or has been generated by atoms in the nebula, which usually makes the nebula appear reddish.
What was the first planet discovered by mathematical prediction?
Neptune
The following images show five planets in our solar system. Rank these planets from left to right based on the amount of time it takes them to orbit the Sun, from longest to shortest. (Not to scale.)
Neptune Jupiter Mars Earth Mercury
The modern spectral classification system enables astronomers to readily "typecast" a star's spectrum and thus determine the star's surface temperature. But why is that so? The key lies in the differing temperature sensitivities of ions, atoms, and molecules. Like Goldilocks and the Three Bears, each ion, atom, and molecule has a preferred range of temperatures for its existence, excitation, and consequent spectral manifestation. Which spectral classes refer to the following physical conditions?
O stars: Too hot for most neutral atoms but okay for some ions B, A stars: Cool enough to host neutral hydrogen and hot enough to excite its electrons to levels that can absorb optical photons F, G, K stars: Cool enough to host neutral heavier elements (metals) and hot enough to excite their electrons to levels that can absorb optical photons M stars: Cool enough to host intact molecules
Which of the following statements correctly describes the motion of the particles in Saturn's rings?
Particles in the inner rings orbit Saturn at a faster speed than particles in the outer rings.
The photos show the same region of space. Which photo do you think was taken with visible light and which do you think is an infrared image?
Photo 1 was taken with visible light; (dark middle) Photo 2 is an infrared image (See through middle)
Pluto was first observed in 1930, and its largest moon, Charon, was discovered in 1978. A few years after Charon's discovery, astronomers were able to observe a series of eclipses as Pluto and Charon passed in front of one another. By studying how the brightness of Pluto and Charon changed as they eclipsed each other, astronomers were able to measure the masses and radii of both Pluto and its moon. What did these measurements imply about the average densities of Pluto and Charon?
Pluto and Charon have average densities that are expected for objects made mostly of water ice
Compare the wave period with the orbital period in the solar photosphere.
PwavePorbitalPwavePorbital = 3.0×10−2
Interstellar dust clouds are best observed at what wavelength?
Radio and infrared
Emission nebulae are distinguished by their bright reddish hue. This characteristic appearance is produced primarily by the excited hydrogen atoms in HII regions. Label the figure with the appropriate components of an emission nebula.
Red wavy line emitted toward observer from outside of cloud: Re-emitted visible light Center cross shapes in middle of nebula: Hot stars Label on red cloud shape: HII region Blue wavy line emitted from inside center of cloud: UV radiation Explanation: The two primary components to an emission nebula are a cloud of hydrogen gas and one or more hot O- or B-type stars. The hot stars emit ultraviolet radiation, which heats the hydrogen gas to the point where electrons are ejected from the hydrogen atoms, thus ionizing the gas. As some of the now free electrons recombine with the hydrogen nuclei, they emit visible radiation, causing the gas to glow in the red part of the visible spectrum.
Listed following are events or phenomena that occur during either the part of the sunspot cycle known as solar minimum or the part known as solar maximum. Match these items to the correct part of the sunspot cycle.
Solar Maximum: -Occurs about 11 years after a solar maximum (on average) -Solar flares are most common -Auroras are most likely in Earth's skies -Sunspots are most numerous on the Sun -Orbiting satellites are most at risk Solar Minimum: -Occurs about 5 to 6 years after a solar maximum (on average)
Our most detailed knowledge of Uranus and Neptune comes from
Spacecraft Exploration
Suppose Star A and Star B have the same absolute brightness. Star A is located some distance away from you, and Star B is twice as far away. You would expect that
The parallax angle of Star B would be smaller than that of Star A.
Why does the surface of the Sun appear to have a sharp edge?
The photosphere is thin compared to the other atmospheric regions.
Match the words in the left-hand column to the appropriate blank in the sentences in the right-hand column. Use each word only once.
The radius of a white dwarf is determined by a balance between the inward force of gravity and the outward push of "electron degeneracy pressure." A(n) "nova" occurs when hydrogen fusion ignites on the surface of a white dwarf in a binary system. A(n) "massive star supernova" occurs when fusion creates iron in the core of a star. A white dwarf in a close binary system will explode as a supernova if it gains enough mass to exceed the "white dwarf limit (1.4 solar masses)". A(n) "accretion disk" consists of hot, swirling gas captured by a white dwarf (or neutron star or black hole) from a binary companion star. A(n) "white dwarf supernova" can occur only in a binary system, and all such events are thought to have the same luminosity.
What causes the blue color associated with reflection nebulae?
The reflection nebula is a cloud of dust. When light from a star encounters this cloud, the short wavelength blue light "bounces back" from the cloud towards us, and the longer wavelength red light passes through.
Following are the four fundamental forces. Rank these forces from left to right based on their relative strengths between two protons separated by a few centimeters, from weakest to strongest. If you think two (or more) forces have equal strength (or essentially zero strength) in this case, show the equality by dragging one on top of the other(s).
The strong and weak forces generally have effects only within atomic nuclei; on larger scales — meaning anything larger than about the size of an atom (which is thousands of times larger than a nucleus) — both the strong and weak forces have essentially zero effect, which is why they are ranked equally here. Gravity and the electromagnetic force both follow an inverse square law with distance; however, for two individual charged particles, the electromagnetic force is far stronger than gravitational force. The strong and weak forces generally have effects only within atomic nuclei; on larger scales — meaning anything larger than about the size of an atom (which is thousands of times larger than a nucleus) — both the strong and weak forces have essentially zero effect, which is why they are ranked equally here. Gravity and the electromagnetic force both follow an inverse square law with distance; however, for two individual charged particles, the electromagnetic force is far stronger than gravitational force.
Which of the following is NOT true of the Jovian planets when compared to Earth?
They all have greater density.
Why are dark dust clouds largely misnamed?
They contain much more gas than dust.
Why are the most common stars among the most difficult to observe?
They have low luminosities. Submit
Which statement about Jupiter's rings is true?
They lie inside Jupiter's Roche Limit. Submit
What makes Titan unique among the moons of the solar system?
Thick, cloudy atmosphere
The arrows point to two of Neptune's moons. Neptune's largest moon, Triton, shown at the left arrow, is in a retrograde orbit. As a result, Triton is slowly moving closer to Neptune. Which of the following will NOT be the distant future fate of Triton?
Triton will stop moving toward the planet when it reaches the Roche limit.
600 million metric tons of hydrogen is converted to energy each second by the Sun.
True
All four jovian planets spin faster than any of the terrestrials.
True
All stars have roughly the same luminosity after the helium flash.
True
Dark dust clouds are optically invisible, but give off radio energy.
True
Despite the gradual decrease in density and temperature of the Sun with distance from its center, the Sun's photosphere shows a reasonably sharp "edge."
True
Elements heavier than iron are formed mainly in supernovae.
True
Fusion occurs at the center of the Sun because that is where the temperature is highest.
True
Jupiter puts back into space twice the energy it gets from the Sun.
True
Most naked-eye stars would fall to the top left on the H-R diagram.
True
Most of the solar wind is generated by material escaping the Sun from coronal holes.
True
Neptune has a larger fraction of methane in its atmosphere than Uranus.
True
Saturn is less dense than water.
True
Sunspots are localized cool spots on the surface of the Sun.
True
The Moon does not block all of the light from the Sun during total solar eclipses.
True
The Sun produces energy by fusing hydrogen into helium.
True
The Sun rotates faster at the equator and slower at its poles, just like Jupiter and Saturn.
True
The Sun will get brighter as it begins to run out of fuel in its core.
True
The average density of the Sun is the same as that of Jupiter.
True
The most abundant element in the Sun is hydrogen.
True
The pressure in the photosphere affects the width of spectral lines.
True
The solar wind is constantly removing mass from the Sun.
True
We have observed a comet strike Jupiter.
True
Young open clusters contain a lot of hot, young blue-white stars.
True
Which of the planets below has the greatest tilt of its rotation axis?
Uranus
In brightness, Jupiter is second only to the planet _____ most of the time.
Venus
The magnetic fields in all planets are generated by the dynamo effect, caused by rapidly rotating and conducting material flowing in the interiors of the planets. We have just seen that all four of the jovian planets have magnetic fields. Earth also has a planetary magnetic field, but Venus does not, although it is very similar to Earth in mass. Which of the following would be a reason why Venus does not have a magnetic field?
Venus's very slow rotation rate does not allow a magnetic field to form.
Which statement is true about the interstellar medium?
We know more about the gas than the dust.
Following are the four fundamental forces. Rank these forces from left to right based on their relative strengths acting between Earth and the Sun, from weakest to strongest. If you think two (or more) forces have equal strength (or essentially zero strength) in this case, show the equality by dragging one on top of the other(s).
Weak and Strong (on top of each other) are weakest; then Electromagnetism, then Gravity (strongest)
Stellar nurseries, such as the Orion nebula, contain hundreds or more fragmenting and contracting regions, as well as many protostars and stars. What condition would allow a protostar to become a stable star?
When a protostar becomes hot enough for nuclear fusion to start, thermal pressure can balance the force of gravity.
What are the characteristics of an open cluster of stars?
a few hundred, mostly main-sequence stars
Many scientific discoveries are made by chance. While studying one phenomenon, a scientist may discover a different one. Such was the case when William Herschel discovered the planet Uranus in 1781. Herschel was charting faint stars in the sky, when he discovered something that was not a star. How can astronomers tell the difference between a star and a planet?
a star b star c star d planet
Of the following star colors, which one indicates the hottest star?
blue
According to Figure 7.9 (Jupiter's Atmosphere) in the textbook, if ammonia and ammonium hydrosulfide ice were transparent to visible light, Jupiter would appear
bluish
A cloud fragment too small to collapse into a main sequence star becomes a
brown dwarf.
Which of the following layers of the Sun can be seen with some type of telescope? Consider all forms of light, but do not consider neutrinos or other particles.
chromosphere, photosphere, corona
The following figures show various stages during the life of a star with the same mass as the Sun. Rank the stages based on when they occur, from first to last.
contracting cloud of gas and dust, protostar, main sequence G star, red giant, planetary nebula, white dwarf
Provided following are various stages during the life of a high-mass star. Rank the stages based on when they occur, from first to last.
contracting cloud of gas and dust, protostar, main sequence star, red supergiant, supernova, neutron star
Compared to a high-luminosity main-sequence star, stars in the upper right of the H-R diagram are __________.
cooler and larger in radius
In which of the following layer(s) of the Sun does nuclear fusion occur?
core
Rank the following layers of the Sun based on the pressure within them, from highest to lowest.
core, radiation zone, convection zone, photosphere
Rank the following layers of the Sun based on their temperature, from highest to lowest.
core, radiation zone, convection zone, photosphere
Rank the layers of the Sun based on their density, from highest to lowest.
core, radiation zone, convection zone, photosphere, chromosphere, corona
From inside out, which is in the correct order for the structure of the Sun?
core, radiative zone, convective zone, chromosphere
Listed following are the different layers of the Sun. Rank these layers based on their distance from the Sun's center, from greatest to least.
corona, chromosphere, photosphere, convection zone, radiation zone, core
Alternating zones of rising and sinking gas in Jupiter's atmosphere
create light and dark bands.
How far would a spacecraft moving in a circular orbit 500 km above Pluto's surface travel during that time?
d = 2.9×104kmkm
What causes the striking red color associated with some parts of many emission nebulae?
electrons in hydrogen atoms making transitions from their n = 3 to n = 2 atomic states
The red/pink color associated with star-forming regions is due to what kind of process?
emission
When an electron in a hydrogen atom changes its spin from the same to the opposite direction as the proton, it
emits a radio wave photon.
A blue star on the main sequence will live a long time compared to our Sun, because it is so massive.
false
A star's absolute magnitude is dependent on its distance from the observer.
false
A star's proper motion is the motion observed due to the movement of the Earth around the Sun.
false
All four ring systems orbit the equators of Jovian planets outside their Roche limits.
false
All stars with the same surface temperature are approximately the same in brightness.
false
As a star evolves away from the main sequence, its surface becomes hotter.
false
Brown dwarfs are the coolest red dwarfs.
false
Callisto has a smooth surface, indicating that it is very young.
false
Compared to other stars, the Sun's mass is about average.
false
Dust grains tend to destroy interstellar molecules.
false
Europa is especially interesting because of the evidence that there is life there.
false
Helium from the intermediate stages of stellar nuclear burning collects at the surface of the hydrogen layers of a main-sequence star, due to its lower density.
false
Hot interstellar clouds will form into stars more quickly than the cold clouds because the required reactions will occur more quickly at higher temperatures.
false
In very massive stars, the helium flash is so violent that the star is blown apart in an event known as a supernova.
false
Interstellar matter is quite evenly distributed throughout the Milky Way Galaxy.
false
Jupiter is nearly large enough to have become a star.
false
Once they have reached the main sequence, stars evolve along this track in sequence from M, K,...through O.
false
Pluto's moon Charon is one of the smallest in the solar system.
false
Recurrent nova outbursts are caused by the repeated cycling of supergiant stars from carbon-burning to helium-burning phases.
false
Reflection nebulae occur when two identical nebulae are located near each other.
false
Supernovae can be detected visually only if they occur within a few parsecs of Earth.
false
The "dust lanes" and other dark patches that block light from parts of many emission nebulae as viewed from Earth are generally due to other separate interstellar clouds that lie between us and those nebulae.
false
The Doppler effect is used to determine a star's transverse velocity.
false
The Galilean moons of Jupiter are quite similar to each other in density, size, and surface cratering.
false
The densities of the larger moons of Saturn suggest they are composed mostly of rock and metal.
false
The density of the photosphere is about the same as the density of the Earth's atmosphere.
false
The different spectral classes of stars are due to the differences in composition between the different stars.
false
The dust particles have exactly the same chemical composition as the gases of the interstellar medium.
false
The spectra of the youngest (i.e., most recently formed) stars show fewer heavy elements than do those of older but otherwise similar stars.
false
The typical spectrum of a star is an emission or bright-line spectrum.
false
Titan is able to retain an atmosphere in spite of its size because it is very dense, causing a strong surface gravity.
false
We can only measure the sizes of stars in eclipsing binary systems.
false
Solar energy is produced by
fusion of light nuclei to make heavier ones
The energy generated in the core of the Sun is transported to the surface by radiation in the radiation zone and then by convection in the convection zone. Radiation occurs when atoms in the interior of the Sun transfer energy by absorbing and reemitting photons in random directions. Convection occurs when energy is transported by a region of hot gas rising up and a region of cooler gas sinking down to take the place of the hotter gas. Since radiation takes place deep within the Sun's interior, it cannot be directly observed. However, convection can be observed due to its effects on the solar surface. Which of the following surface features provide evidence for solar convection?
granulation & supergranulation
When a newly forming star is at its greatest luminosity, what is its energy source?
gravitational contraction
A white dwarf can dramatically increase in brightness only if it
has another star nearby.
Cometary impacts with Jupiter
have been observed from Earth at least twice.
Hydrogen-shell burning proceeds increasingly faster due to which of the following?
heat released from the core's contraction
Provided following are various elements that can be produced during fusion in the core of a high mass main sequence star. Rank these elements based on when they are produced, from first to last.
helium, carbon, oxygen, iron
Compared to a low-luminosity main-sequence star, stars in the lower left of the H-R diagram are __________.
hotter and smaller in radius Submit
As a clump of interstellar gas contracts to become a main-sequence star, its changing position on the H-R diagram tells us __________.
how its outward appearance is changing
Of the elements in your body, the only one not formed in stars is
hydrogen
The strongest lines present in spectral class A stars are absorption lines of
hydrogen
Small deviations in a planet's orbital motion
imply the nearby presence of a massive body. Submit
When a star's inward gravity and outward pressure are balanced, the star is said to be
in hydrostatic equilibrium.
Most stars in our part of the Galaxy are formed
in open clusters of a few dozen.
What kind of light would be the best to use to look inside a cold dark cloud and see the warm stars forming inside?
infrared
Studying the magnetospheres of the jovian planets has allowed us to measure their
interior rotation rates.
During a period of high solar activity, the corona
is more irregular.
Callisto is different from the other Galilean moons of Jupiter in that ________.
it doesn't have an iron/iron sulfide core
Provided following are stages that occurred during the formation of our solar system. Rank these stages from left to right based on when they occurred, from first to last.
large cloud of gas and dust, contraction of solar nebula, condensation of solid particles, accretion of planetesimals, clearing the solar nebula
Infrared radiation has a longer wavelength than visible light. Compared to visible light, do you expect infrared radiation to be affected more, less, or the same by interstellar dust?
less
Compared to a main-sequence star with a short lifetime, a main-sequence star with a long lifetime is __________.
less luminous, cooler, smaller, and less massive Submit
Estimate the life expectancy of a 10-solar mass, 2000-solar luminosity blue giant.
lifetime = 5×10^-2 billion years
Saturn's rings look bright because __________.
light from the Sun reflects off the material in the rings
To explain its magnetic field, Europa must have an ocean of
liquid water
Which of the Galilean moons is densest and most geologically active?
lo
Saturn's rings are composed of __________.
lots of individual particles of ice and rock
What property of a star cluster helps determine its age?
main-sequence turnoff
Compared to the underlying photosphere and chromosphere, the corona is _____ in temperature.
much hotter
A main-sequence star twice as massive as the Sun would last __________.
much less than half as long as the Sun
Which of the following is a particle produced in the proton-proton fusion reaction?
neutrino -These neutrinos are detected here on Earth as evidence that these nuclear reactions are taking place in the center of the Sun.
Black dwarfs are
not found yet; the oldest, coldest white dwarf in the Galaxy has not cooled enough yet.
What best explains the darkness of the rings beyond Saturn's?
old, sooty debris and radiation darkening
What would Spica's parallax be if it were measured from an observatory on Neptune's moon Triton as Neptune orbited the Sun?
parallax = .36 Arc Seconds
Which of these evolutionary paths is the fate of our Sun?
planetary nebula
The balance between gravity and _____ creates the internal structure of stars.
radiation pressure Submit
While many elemental spectral lines are visible, almost all molecular lines lie in the _____ portion of the spectrum, since they are at much lower energy.
radio
What is the primary visible color of an emission nebula?
red due to the Hα line of hydrogen
Which of these is not a consequence of dust in the interstellar medium?
red light from the emission nebulae
In general, the more massive the star, the _____ its lifetime.
shorter
The "dust" component of the interstellar medium is mostly particles of about what size?
smoke particles
Which observation reveals the presence of certain elements in the star's atmosphere?
spectral absorption lines
Assume that all four H-R diagrams below represent a star in different stages of its life, after it starts to fuse hydrogen in its core. Rank the HR diagrams based on when each stage occurs, from first to last.
star in the sequence a little outside more outside then below the line
In a very young star cluster, while the most massive stars are swelling up into giants, the least massive stars are
still on the zero-age main sequence.
What is the round-trip travel time of light from Earth to Pluto (at a distance of 40 AU)?
t = 11hours
What physical property of a star does the spectral type measure?
temperature
Which of the following rings of Saturn lies closest to the planet?
the C ring
Which of the following is true?
the deeper you dive into the atmospheres of the outer planets, the higher the temperature.
Generally, you would expect that the closer a moon is to a large planet,
the warmer its interior
A protostar becomes a true star when its central temperature reaches 10,000,000 K, high enough to ignite nuclear fusion.
true
A protostar can develop a photosphere even if it does not initiate nuclear fusion.
true
A star can become a nova more than once, but it can become a supernova only once.
true
A star spends much more time on the main sequence than it spends forming initially.
true
A star with a parallax of 0.25 arc seconds is twice as far away from us as one with a parallax of 0.5 arc seconds.
true
A star's luminosity and its absolute magnitude are two different ways of expressing the power output of a star.
true
A star's size is determined by the equilibrium established by the inward force of gravity and the outward pressure generated by a hot gas.
true
A supernova ejects material into the interstellar medium that has different relative amounts of heavy elements than the stuff out of which the star originally formed.
true
After the Sun leaves the main sequence, it will evolve into a red giant.
true
Although sunspots are cooler areas in the photosphere, when they increase in number that tells us the Sun is becoming more active.
true
Apparent magnitude refers to the brightness of stars as seen from Earth.
true
As an interstellar cloud fragment collapses to form a star, its internal temperature increases steadily.
true
Binary stars are the only class of stars for which we can determine stellar masses directly.
true
Both Europa and Ganymede may have liquid water beneath their surfaces.
true
Dark dust clouds may appear bright in the radio region of the spectrum.
true
Eclipsing binaries give us data on the sizes of stars.
true
Emission nebulae are associated with star formation.
true
Fewer than 100 stars lie within 5 parsecs of the Sun.
true
Ganymede appears to have "maria" similar to those on Earth's Moon.
true
Heavier stars move more quickly through the evolutionary stages that lead to their formation than do lighter ones.
true
High-mass stars generate sufficient temperatures to burn their residual carbon ash during later stages of their evolution.
true
Io has a volcano that emits more energy than all the volcanoes on Earth combined.
true
Isolated stars with masses less than 8 times that of our Sun never reach sufficiently high temperatures and pressures to burn carbon at their cores.
true
It is possible to determine the temperature of a star by measuring the star's apparent brightness at two different wavelengths.
true
It is possible to estimate the age of a star cluster from its H-R diagram.
true
The rings of Uranus are dark, narrow, and widely spaced from each other.
true
The stars in a given cluster all formed at the same time and have the same composition.
true
The surfaces of some stars, even some very bright ones, are cool enough to allow molecules to form.
true
The total mass of all the objects in the Kuiper Belt may be dozens of times the mass of the entire asteroid belt.
true
There is as much mass in the voids between the stars as in the stars themselves.
true
Titan has lakes of liquid methane and even streams of liquid methane.
true
Two of the Galilean moons of Jupiter are the size of Mercury, and the two others are about as big as our own Moon.
true
Uranus has no large moons.
true
When the Sun becomes a red giant, its photosphere may reach the orbit of Mercury.
true
White dwarfs do not produce new energy; they just radiate away excess energy as they cool.
true
Each supernova type is distinct in initial components, process, and observational properties. Sort the following characteristics as to whether they describe a Type I or Type II supernova.
ype I: - low-mass star - hydrogen-poor - carbon-detonation supernova - graph with green line (initial increase followed by steady decrease) Type II: - high-mass star - hydrogen-rich - core-collapse supernova - graph with red line (higher initial luminosity but luminosity constant from 25 to 100 days before decrease)
Determine the wavelength corresponding to the peak of the black-body curve just below the solar photosphere (10^4 K). What form does the radiation take?
λ10^4K = 290nm Near UV
Given that the solar spectrum corresponds to a temperature of 5800 KK and peaks at a wavelength of 500 nmnm, use Wien's law to determine the wavelength corresponding to the peak of the black-body curve in the core of the Sun, where the temperature is 10^7 K. What form does the radiation take?
λ10^7K = 0.29nm Hard X-ray
Compare your answer with the Sun's gravitational force on Uranus.
• F Uranus- Sun / F Uranus - Neptune = 4600
