ASTR 2010
Which of the following actions would increase the gas pressure inside a balloon? Select the most complete answer with respect to the following options: (1) Add more gas inside the balloon (2) Remove gas from inside the balloon (3) Heat up the gas inside the balloon (4) Cool down the gas inside the balloon
(1) and (3)
A star at a distance of 42 parsecs has an apparent magnitude of +3.60. What is its absolute magnitude? Give your answer to 2 digits past the decimal point (ie in #.## format).
+0.48
A star Delilah is measured to have its blue (B) magnitude of 2.8, while its red (R) magnitude is measured to be 1.6. What is this star's B-R color index?
+1.2
A galaxy has an absolute magnitude of -20, and is at a distance of 10,000,000 parsecs (10 megaparsecs). What is its apparent magnitude?
+10
Star C is at a distance of 10 parsecs, and has an apparent magnitude of +3. What is its absolute magnitude? HINT: you don't need an equation for this one!
+3
The star Sirius has a magnitude of -1.44. What would the magnitude of a star be that appeared to be 100 times fainter than Sirius?
+3.56
A star has an apparent magnitude of +5, and is at a distance of 10 parsecs. What is its absolute magnitude?
+5
A star with absolute magnitude +2 is at a distance of 100 parsecs. What is its apparent magnitude? Answer
+7
A star with absolute magnitude +4.65 (the same as the Sun) is at a distance of 100 parsecs. What is its apparent magnitude?
+9.65
Star D has an apparent magnitude of +1, and is at a distance of 100 parsecs. What is its absolute magnitude?
-4
What would the magnitude of a star be which appeared to be 100 times brighter than Vega?
-5
Distance affects the appearance of a light in what way (if any)?
. As a light source gets further away, the light appears dimmer, with the light dimming by a factor of 4 if the distance doubles.
If the distance to a star is 23 parsecs, what is its parallax angle?
0.0434 arcseconds
The acceleration due to gravity on the surface of Mars is 3.7 m/s2. If one were located at a location 3 Mars radii away from the center of Mars (or 3 times further away), what would the acceleration due to gravity of Mars be at that location?
0.41 m/s^2
An incandescent light bulb produces 300 Watts of light (i.e. has a luminosity of 300 W). What is the brightness (flux per meter squared) at a distance of 20 meters from the bulb?
0.597 Watts per meter squared.
A space probe receives 2300 Watts per meter squared (flux) from the Sun. The Earth (at 1 AU) receives 1300 Watts per meter squared (flux) from the Sun. At what distance from the Sun is the space probe? Give your answer to AU, to 2 significant digits.
0.75
Place the phases of one solar-mass post-main sequence evolution in their proper order.
1. First Red giant phase 2.Helium flush 3 horizontal branch phase 4.second/asymptotic giant phase 5.Planetary nebula ejection 6.white dwarf
Put the following steps of post main-sequence evolution of a one solar-mass star in the proper order.
1. Main sequence 2. First red giant 3. Helium Flash 4. Horizontal branch 5. second red giant 6. Planetary nebula ejection 7. white dwarf
What is the lifetime of a star with mass 10 solar masses and luminosity of 10,000 solar luminosities?
10,000,000 years (or 107 years)
If a star has a parallax angle of 0.001 arcseconds, what is the distance to that star?
1000 parsecs
A star with an absolute magnitude of +3 is observed to have an apparent magnitude of +13. What is its distance?
1000 pc.
The absolute magnitude of a Type Ia supernova at peak brightness is -19.2. If a Type Ia supernova were observed to have a peak apparent brightness of magnitude 5.8, what would the distance to the supernova be?
106 or 1 million parsecs.
The most massive star still on the main sequence in a certain cluster of stars is 10 solar masses, with a luminosity of 10,000 solar luminosities. What is the age of the cluster?
107 years (10 million years)
if the wavelength of a wave is 14 meters and the frequency is 10 sec^-1, what is the speed of the wave?
140 meters/sec
The hydrogen emission line normally observed (in the lab) to be at 656.3 nm is seen at 659.4 nm in a stellar spectrum. How fast and in what direction is the emitting star moving? [The speed of light is 3*105 km/s]
1417 km/s away from us.
Match the following main sequence stars to the proper final result state (once all stellar evolution is complete).
2 solar-mass main sequence star=white dwarf 0.2 solar-mass main sequence star=helium ball 15 solar-mass main sequence star=neutron star 75 solar-mass main sequence star=black hole
If the frequency of a wave is 20 sec^-1 and the speed of the wave is 20 m/s, what is the wavelength of the wave?
20 meters
Star Vader is observed to shift by 0.1 arcseconds in comparison to distant galaxies between observations in July and January. This results in the star having a parallax angle (p) of 0.05 arcseconds (see the diagram in the notes). What is the distance to the star in parsecs?
20 parsecs.
Your car gets stuck in the snow in a parking lot. A friend attempts to push it out of the snowbank, applying 200 Newtons (kg m/s2) of force to the car. With what force does the car push on your friend?
200 Newtons
A given light source produces enough energy to give a brightness of 20 Watts per meter squared at a distance of 10 meters. At what distance will the brightness be 0.05 Watts per meter squared?
200 meters
The frequency of the BGSU radio station WBGU FM is 88.1 MHz (megahertz). What is the wavelength of the light emitted by the transmitter for this station in meters? The speed of light is 300,000,000 meters/second.
3.405 meters
You are listening to the BGSU radio station WBGU FM, which has a frequency of 88.1 MHz (88,100,000 Hz). How fast are the radio waves travelling from the transmission tower to your radio?
300,000,000 meters/second.
A star has a surface temperature of 9350K. At what wavelength does its spectrum have the highest intensity (i.e. what is the wavelength of peak emission)? Give your answer in nanometers (nm), to 2 significant figures
310.0 (with margin: 15.0)
Which is the hottest temperature, 32 degrees K, 32 degrees C, or 32 degrees F?
32 degrees C
How much force would be needed to accelerate a 20 kg. box at 2 m/s2?
40 N
Star Manning is observed to have a parallax angle of 0.025 arcseconds. What is the distance to the star in parsecs?
40 parsecs.
A lightbulb produces enough energy to give a brightness of 3.537 Watts per meter squared at a distance of 3 meters. What is the luminosity (total energy output) of the bulb?
400 Watts
An object is observed to be radiating light, with the peak of the emission occurring at 5800 nm. At what temperature is the emitting object?
500 K
The Earth receives 1300 Watts per square meter (flux) at its surface from the Sun. If we launch a space probe into orbit around Jupiter, at a distance of 5 times the Earth-Sun distance, how much light reaches the solar panels? Give your answer in Watts per square meter (flux), to 2 significant digits?
52
We receive a flux of 10,000 photons per second from object #1, while we receive a flux of 160,000 photons per second from object #2. If the temperature of object 1 is 273 K, what is the temperature of object #2? Assume the objects are the same size. *Hint: Look at the ratio of the fluxes to figure out the temperature increase. You can't directly plug the flux into the F~T4 law because the flux in the equation is in photons per second per square meter and I don't give you the size of the object.
546 K
A star is moving at 1500 km/s directly towards us. Helium absorption lines are normally seen at 587.5 mn (yellowish light). At what wavelength will we observe the absorption line? [The speed of light is 3*105 km/s] [Hint: should the observed wavelength be shorter or longer than the normal (rest) wavelength?]
584.56 nm
A given box masses 60 kg. Pushing as hard as you can, you are able to accelerate the box at 2 m/s/s. Again pushing as hard as you can, how fast could you accelerate a box massing 20 kg? Answer
6 m/s/s = acceleration of 20 kg box
Star E has an absolute magnitude of +2.3, and is at a distance of 67 parsecs. What is its apparent magnitude?
6.43
A star has a surface temperature of 4,500 K. What is the wavelength of peak emission (i.e. the wavelength of light with the most emission)?
644.4 nm
A given light source produces enough energy to give a brightness of 20 Watts per meter squared at a distance of 10 meters. What will be the brightness at a distance of 5 meters?
80 Watts per meter squared
We see a lamp known to have a 100 watt light bulb at a distance of 20 feet. We see another lamp at a distance of 60 feet. How many 100-watt light bulbs must be in the second lamp to make it appear to be the same observed brightness as the first lamp (so both lamps appear to the observer to be the same brightness)? You may assume that each 100-watt light bulb produces the same fixed amount of light.
9.0 (with margin: 0.1)
We are building a model of the Solar System, and choose to use an object which is 10 inches across to represent the Earth. How large of an object should we use to represent Saturn? The Earth has a diameter of 12,756 km, while Saturn has a diameter of 116,464 km. Give your answer to 1 decimal place, or ##.#; do not include units in your answer (your answer should be in inches).
91.3 (with margin: 2.0)
The hydrogen emission line normally observed to be at 656.3 nm is seen at 658.3 mn. How fast and in what direction is the emitting object moving? [The speed of light is 3*105 km/s]
914 km/s away from us.
What kind of star system is most likely to result in a Type Ia supernova?
A 1.8 solar-mass star orbited by a 1.2 solar-mass star at a spacing of 0.04 AU (i.e. much closer than Mercury is to our Sun).
The normal light detector used in astronomy research today is
A CCD camera.
Two stars (A&B) produce the same amount of light (so have the same absolute magnitude), but A is further away than B. Which of the following statements must be true?
A appears dimmer, and thus has a higher apparent magnitude, than B
Which of the following light bulbs, all 100 Watt, will appear the faintest to the eye?
A bulb 300 feet away
What is a sunspot?
A dark spot on the surface of the Sun, caused by a kink in the Sun's magnetic field interrupting the convection flow in the Sun.
What are twoe differences between a globular cluster and an open cluster?
A globular cluster is formed of old stars and is located in the galactic halo, while an open cluster is formed of young stars and is located in the galactic disk. Remember that open clusters are the remnants of recent star formation, being the cluster of stars left behind when the remaining molecular cloud is blown away.
What is located at the center of the Milky Way?
A large black hole.
Which of the following molecular clouds could have formed the Sun?
A molecular cloud with about 98% hydrogen and helium, and 2% heavier elements.
Astronomers are able to determine that a star is moving away from us at a speed of 27 km/s simply by taking a spectrum of the star. How is this possible?
A set of absorption lines due to a specific element are found to all be red-shifted by the same amount as compared to the positions in the lab.
Which is the dimmest star?
A star with magnitude +4.65
Which is the brightest star?
A star with magnitude -5
Based only on the spectral classification, what can we say for certain about A stars as compared to M stars?
A stars are hotter than M stars.
Which of the following events is thought to trigger the initial collapse of a previously-stable giant molecular cloud?
A supernova explosion in the close neighborhood of the cloud.
What fills the space between the stars?
A thin (few atoms/cubic centimeter) distribution of primarily hydrogen and helium.
How does the appearance of an young cluster's H-R diagram differ from that of an old cluster?
A young cluster will have high-mass main sequence stars (spectral type OBA), while the low-mass stars may not yet have settled onto the main sequence. An old cluster will have only low-mass (GKM) main sequence stars.
: If the acceleration due to gravity on the surface of the Earth is 10 m/s/s., what would the acceleration due to gravity be at a location 5 Earth radii from the center of the Earth?
A(g) = 10 / (5^2) = 10/25 = 0.4 m/s
A spectrum is observed to show most colors of light, but a few colors are missing (leaving black bands across the rainbow of colors). Which type of spectrum is this?
Absorption spectrum
Two objects (A and B) are dropped from a high building at the same time. They have similar sizes and shapes, but object A is twice as massive as object B. Which of the following statements about how they fall is true?
All objects under the influence of gravity accelerate at the same rate; therefore (neglecting air resistance, which in this problem is negated by saying the two objects have the same shape) the two objects will hit the ground at the same time. The force on object A is higher (by F=m*a) but the higher force is pushing on a more massive object so it doesn't accelerate more quickly.
Why are type Ia supernovae useful as standard candles?
All of the other answers are correct.
Which phase or phases of one solar-mass post main-sequence evolution involve a degenerate core?
All phases after main sequence except for the horizontal branch phase.
Which of the following stars has the longest main-sequence lifetime?
An M-class star, much cooler and dimmer than the Sun.
[Returning to normal questions now] Of the following stellar properties, which can be directly measured by astronomers, with no other information or interpretation needed?
Apparent brightness in magnitudes
What is the Big Bang Theory?
As science is limited to looking at nature to understand nature, the Big Bang theory is 'a scientific explanation of what happened after the Universe came into existence.' Since space/nature did not exist at/'before' the 'beginning' of expansion, science cannot say anything about the cause of the Big Bang or what happened before time and space untangled at 10^-43 seconds. There IS, however, good evidence supporting the Big Bang theory from after that time.
Why is astrology not considered to be a science? Give 2 specific reasons as covered in class.
Astronomy does not yield objective truth, astrology ascribes a qualitative dimension to time which is not acknowledged by science. Astronomy has not objective and testable mechanisms to explain how it works and it is hard to prove something through the standards set by science.
As a star is forming, matter continues to fall inwards onto it and thus increases the mass of the star. When does this process of mass infall stop?
At the point of the development of strong winds from the forming star which halt the flow of material onto the core.
Temperature is a measure of what property of a substance?
Average kinetic energy of the molecules within the substance.
Which of the indicated stars on the picture below is the coolest?
B (2nd from left)
If a star is producing 2.5 times as much red light than it is blue light, what will its B-R color index be? Hint: what is the magnitude difference for a brightness difference of 2.5?
B-R = 1.0
The Milky Way galaxy is what class of galaxy?
Barred Spiral
The helium flash in a solar-mass star generates a tremendous amount of energy within the star in a very short time. Why does this not destroy the star?
Because much of the energy goes to lift electron degeneracy in the core, the rest expands the inner portions of the envelope against gravity.
How do we know that interstellar gas exists?
Because of optical emission lines (produced by hot hydrogen), radio emission (produced by cold gas), and absorption features in stellar spectra added by cold interstellar gas.
Why are Cepheid variable stars useful distance indicators for measuring the distances to stellar clusters?
Because the period of their variability is directly related to their luminosity.
Two skydivers jump out of a plane. One masses (with equipment) 80 kg. while the other masses 100 kg. How does the acceleration due to gravity and the force due to gravity compare for the two skydivers? Note: Neglect air resistance in this problem.
Both accelerate at the same rate; the force due to gravity on the 100 kg skydiver is 25% more (1.25 times) than the force on the 80 kg. skydiver.
Two objects are dropped off the roof of the Student Union. The first masses 12 kg., while the second masses 60 kg. Assuming no effects of friction/air resistance, how do the accelerations due to gravity of the two objects compare, and how do the forces on the two objects compare?
Both objects accelerate due to gravity at the same rate. so the 12 kg. object feels 1/5th the force of the 60 kg object, or the 60 kg. object feels 5 times the force that the 12 kg. object feels.
How is galaxy luminosity related to galaxy type?
Both spiral and elliptical galaxies vary widely in total brightness (luminosity). There seems to be no trend of type of galaxy vs. luminosity, unlike in the case of main sequence stars where hotter stars are always brighter.
What are the two visible properties of stars?
Brightness and color
Two stars (Calvin and Hobbes) are known to have the same temperature, and thus the same light output per unit surface area. However, Calvin puts out 9 times more light than does Hobbes. How is this possible (or is it)?
Calvin has a radius 3 times larger than does Hobbes, thus a surface area 9 times larger to emit light.
A hot dense material which gives off light (like the filament of a lightbulb) emits what type of spectrum?
Continuum spectrum
What process transports energy through the upper layers (say top 25% of the radius) of the Sun?
Convection helps move energy through the upper layers of the sun
Three stars emit known amounts of light (luminosity): Star "Larry" has the same luminosity as the Sun, star "Moe" has 0.1 times the luminosity of the Sun, and star "Curly" has 10 times the luminosity of the Sun. Assuming all three stars are on the main sequence, rank the stars in order of mass, from highest to lowest mass.
Curly, Larry, Moe
What effect of light passing through glass is problematic for astronomers using large refracting telescopes?
Different colors of light are bent different amounts, and thus are brought to focus at different places.
Two stars are observed. One star (Dilbert) has an apparent magnitude of 4.6, while the second star (Dogbert) has an apparent magnitude of 6.6. How much brighter does Dilbert appear as compared to Dogbert (i.e. how much more light do we receive from Dilbert)?
Dilbert is 6.25 times brighter than Dogbert.
Where does most star formation take place in spiral galaxies?
Disk (in the arms).
Two stars (Dilbert and Dogbert) have the same apparent magnitudes, but Dogbert is 2 times further away than Dilbert. Which of the following statements gives both possible explanations for this?
Dogbert is hotter or larger than Dilbert
What is the cause of astronomical 'reddening'?
Dust absorbing blue light more easily than red light is the cause of interstellar reddening, making stars appear redder than they otherwise would. Motion of stars away from us would also cause stars to appear redder than they otherwise would (they would be moving VERY fast for us to actually see the effect with our eyes), but this is called the Doppler shift of light.
Galaxy collisions are thought to be able to form what type of galaxy?
Elliptical galaxies (from the collision of two spirals).
Which type of galaxy is no longer forming stars?
Ellipticals.
What is responsible for heating the corona of the Sun to a temperature far higher than the photosphere?
Energy is transferred to the thin gases of the corona by the Sun's magnetic field.
Why is the corona of the Sun so hot?
Energy is transferred to the thin gases of the corona by the Sun's magnetic field.
What property of the atom is responsible for the specific colors of emission lines?
Energy levels of the electrons
How is energy carried from the center of the Sun to the surface?
First by radiation (direct transfer of energy by photons), then by convection (transfer of energy by bulk motion of matter).
If a star is twice as large as another (with both having the same surface temperature), how much more light is the larger star producing?
Four times as much
Which of the following types of light has the highest frequency?
Gamma rays
What keeps the Sun balanced against its own gravity?
Gas pressure from the heat of the Sun balances gravity.
Which of the following is typically NOT found in the disk of the Milky Way?
Gas/dust traces star formation, so gas/dust will be associated with young stars, which are often found in open clusters. So all of these answers are pointing to the same region, leaving only the old globular clusters out. The disk of the Milky Way is where star formation occurs, so this is where the gas/dust, young stars, and open clusters are found. Therefore, globular clusters are the object not typically found in the disk.
What property of a cluster of galaxies can be determined by using gravitational lensing?
Gravitational lensing is a property of the mass of the lensing object, so we can use the lensing effects of a cluster of galaxies on background objects to determine the cluster mass.
What is the original source of energy which heats up the core of a collapsing cloud?
Gravitational potential energy of the cloud.
What is the original source of the energy that heats up the core of a collapsing interstellar molecular cloud?
Gravitational potential energy of the cloud.
Stars are made of gas, and any gas will try to spread out under its own pressure. So why do stars not expand over time?
Gravity balances the gas pressure, stabilizing the star.
Why don't stars collapse under their own gravity?
Gravity must be balanced by something or the star would collapse on a human-short time scale. If rotation did the balancing, the poles of the star would fall in (since they are not moving due to rotation; like the Earth's north south poles don't move as the Earth spins) and the star would become a disk. The only thing left is gas pressure, which is trying to expand the gases of the star. The balance between gravity and gas pressure is what keeps the star stable in size.
Four lights (white, red, green, blue) are shone (in succession) on a red shirt. Under which lights will the shirt NOT reflect any light, and thus appear black?
Green and Blue
A galaxy at 50 Mpc will be observed to be moving away from us at what speed (assuming pure Hubble expansion with a Hubble constant of 75 km/s/Mpc)?
Hubble's Law: velocity = H * distance So: velocity = 75 km/s/Mpc * 50 Mpc velocity = 3750 km/s
A galaxy is measured (via the Doppler shift) to be moving away from us at 2250 km/s. Using Hubble's Law and a Hubble term of 75 km/s/Mpc, how far away from us is this galaxy?
Hubble's Law: velocity = H * distance. So: 2250 km/s = 75 km/s/Mpc * Distance (in Mpc) 2250/75 = 30 Mpc
When does hydrogen fusion completely stop in a one solar-mass star?
Hydrogen fusion does not completely stop in a one solar-mass star until the outer layers are removed in the planetary nebula phase. Hydrogen fusion in the core stops earlier, but a shell of hydrogen continues to fuse in all later stages until all fusion stops.
The Sun is made of what materials?
Hydrogen, helium, and small amounts of other materials.
What is the Sun made of?
Hydrogen, helium, and small amounts of other materials.
What is the specific difference (as covered in the class notes) between a scientific hypothesis and a scientific theory? [1 point]
Hypothesis-Proposed explanation for some property of the universe. Must fit current observation/evidence Not well tested or supported Scientific theory-Hypothesis that has been thoroughly tested and verified Never absolute-always subject
What can we say about an M-class main-sequence star in comparison to the Sun?
In terms of main sequence stars only, hotter stars always have more mass (as it turns out, that why they are hotter), are somewhat larger (more mass requires more space), but has a shorter lifetime (the very large increase in luminosity means that it runs out of fuel faster) as compared to cooler stars.
Where is the Sun located within the Milky Way?
In the disk, ~halfway from center to edge.
How does the appearance of an old cluster's H-R diagram differ from that of a young cluster?
In the old cluster, the hot OBA stars have had time to evolve off the main sequence, and thus only the cool stars (with longer main-sequence lifetimes) are still on the main sequence.
If the temperature of an object increases by 20% (i.e. goes up by a factor of 1.2), by how much does the flux (light emitted per unit area) change?
Increases by a factor of 2.07
Why does iron not fuse in a massive star?
Iron is the fusion limit because no fusion (or fission) process can occur with iron which releases energy, so it does not take place normally (except in very special circumstances where insane amounts of energy are available in the region as well).
Which type of galaxy has the most gas/dust in it?
Irregulars
A supernova explodes in an open cluster. What type is it and how do we know?
It is a Type II supernova (death of a massive star), it cannot be a Type Ia supernova because that is an exloding white dwarf and open clusters haven't been around long enough to form white dwarf stars yet.
If we increase the temperature of an object, what must happen to the wavelength of peak emission and the overall color of the object?
It must decrease, resulting in a bluer color.
What is the final fate of a 1 solar-mass star?
It sheds it outer layers as a planetary nebula and leaves behind a white dwarf (a ball of degenerate carbon/oxygen).
If in a fixed volume of gas the pressure increases, what must happen to the temperature?
It will increase.
Three friends walk into a bar. Jill is wearing a white shirt, Jack is wearing a red shirt, and James is wearing a green shirt. When the dancing starts, a green light is used to illuminate the dance floor. Who's shirts match?
Jill and James' shirts match.
What is light?
Light is energy, and has both wave and particle properties (each total wavelength is equivalent to one photon). It needs no 'surface' or material across which to travel.
A hot (30,000K, or 5 times solar temperature) but very dim (0.01 times solar luminosity) star would be located in which corner of the H-R diagram?
Lower left.
First: what would we expect to see if we created an H-R diagram based on a cluster of different mass stars all known to have formed 10 million years ago? A good way to approach this is to look at a range of specific stellar masses (0.1 solar mass, 0.5 solar mass, 1 solar mass, 3 solar mass, 10 solar mass, 50 solar mass). For each stellar mass, assume that the star first reached the main sequence 10 million years ago. Now figure out where they would be located on the H-R diagram: i.e. are they still main sequence, post-main sequence (you may estimate that the post-main sequence phase lasts about 10% of the main sequence lifetime for any star), or at their end-point of evolution?
Mass is a crucial indicator in determining the fate of a star. Starting with the 0.1 and 0.5 solar mass stars, we would expect to see very little movement in an HR diagram from 10 million to 10 billion years. They are slow-burning, with lifetimes that far exceed that range. Their residency status, so to speak, on the main sequence will be the longest tenured. For the 1 and 3 solar mass stars, at 10 million years on the main sequence, these stars are in the prime of their lives, just sitting there fusing hydrogen into helium, doing their thing. By the time we get to 10 billion years, both of these stars are beginning their demise. The 1 solar mass star is just beginning to run out of hydrogen in its core, and the 3 solar mass star will be just a little further along in this process due to its slightly higher mass. It will be moving into the red giant phase with a helium core. Both of these stars will make the transition through red giants, helium flash, planetary nebulae, and ultimately to dwarfs. On to the 10 and 50 solar mass stars...these immense mass of these stars leads to a relatively short life cycle. The 10 solar mass star will have already transitioned into a red supergiant at 10 million years, and quite possibly already experienced its supernova explosion. The 50 solar mass star would have already gone through its supernova explosion and is being returned to interstellar medium. At 10 billion years these stars are long gone, and left over matter is potentially in the forming stages of new stars.
Which of the following particles, all generated by the fusion process in the core of the Sun, is the only one we can directly observe here at Earth?
Neutrinos
What direct evidence do we have about the fusion process which powers the Sun?
Neutrinos emitted by the first step of the proton-proton chain, which travel through the Sun unimpeded and come straight to the Earth.
The Sith Lords (e.g. Darth Vader, etc) have developed a new weapon system which instantly compresses a star into an object the size of the Earth, but leaves its mass unchanged. What happens to the orbits of the planets circling a targeted star?
Nothing would change, the planets would continue to orbit normally since the mass of the star didn't change.
How does the Sun generate energy?
Nuclear fusion.
Object 1 is observed to be emitting most of its light at a wavelength of 320 nm (ultraviolet). Object 2 is observed to be emitting most of its light at a wavelength of 960 nm (infrared). How much hotter is object 1 than object 2?
Object 1 is three times as hot as object 2.
Assuming that the objects are all the same size and at the same distance, which of the following objects has the highest temperature?
Object 5, which glows very brightly
Object A is twice as hot as object B. How does the light emission per unit area of object A compare to the light emission from object B?
Object A emits 16 times as much light per unit area than does Object B.
Which of the following sites would be the best for siting a new astronomical research telescope?
On a high-altitude mountain in a desert far away from large cities.
Which of the following is the hottest object?
One glowing a bluish color
A new weight-loss program claims to be able to decrease your weight substantially by simply having you travel to a "distant location". On further inquiry, you discover that the "distant location" is actually the surface of the Moon. Does this process actually change your body mass? Why or why not?
Ones mass would stay the same but one would weigh differently on the moon. The moon has less mass than the earth so it requires less gravity than the earths. So one would weigh less on the moon than the earth but mass would stay the same.
A group of stars contains only young stars, and is located within the galactic disk. What type of cluster is it?
Open Cluster.
Star 'Pinky' is at a distance of 10 parsecs, while Star 'The Brain' is at a distance of 20 parsecs. They give off the same amount of light. How do the apparent brightnesses of Pinky and The Brain compare?
Pinky appears to be 4 times brighter than The Brain.
Which of the following is NOT important to astronomers in placing a new research telescope?
Proximity to a nearby airport (closer the better)
Two stars (Batman and Robin) have the same apparent magnitude of +3.0, but Robin is 4 times further away than Batman. Explain how we could use this information to conclude that Robin must be hotter than Batman. You may assume that the two stars are the same size; you do NOT need to do any actual calculations here, just describe the process. Tip: there are two steps to the logical process, thus the assigned point value. [2 points]
Robins apparent magnitude would be higher because if it was two times farther away it would appear to be 1/4th brighter than batman. Because they have the same apparent magnitude and one is farther away it would mean that star has more energy to be able to have the same apparent magnitude at a farther distance.
Which phase or phases of one solar-mass post main-sequence evolution involve shell fusion of helium?
Second red giant phase and planetary nebula phase.
Which of the following statements about the final fates of individual stars is correct?
See the last slide from this week's 2nd presentation for the summary.
Why does carbon not ever begin to fuse in a one solar-mass evolving star?
Since carbon has 6 protons in the nucleus, the temperature necessary to overcome the electric proton-proton repulsion is higher (for faster particles) for carbon fusion than it is for helium fusion. The temperature in the core simply never gets hot enough to start this process in a one solar-mass star.
4: An astronaut working on the Space Station tosses a hammer to a coworker. The astronaut (plus suit) masses 75 kg., while the tool masses 3 kg. How does the force on the hammer compare to the force on the astronaut, and how does the acceleration of the hammer compare to the acceleration of the astronaut?
So the acceleration of the hammer is 25 times that of the astronaut, and since the force applied is in the opposite direction the acceleration is in the opposite direction also.
How does the escape velocity from the surface of Mars compare to the circular orbit velocity at the surface of Mars?
So the escape velocity is sqrt(2) higher than the circular velocity at any given location.
How does the force of gravity due to the Earth on a given object change if we move the object from the surface of the Earth to a distance equivalent to the distance of the Moon (60 Earth radii from the center of the Earth)?
So the force of gravity at 60 earth radii is 1/3600 the force of gravity at 1 earth radius.
The escape velocity for an interplanetary space probe (like the Mars Rovers) from the surface of the Earth is 11.2 km/s. What would the escape velocity be for a space probe massing 9 times the mass of the Mars rover?
So the mass of the rocket is irrelevant, the escape velocity doesn't change.
Star A is twice as far from us as star B. How does Star A's parallax angle compare to Star B's?
Star A's parallax angle is 1/2 that of Star B.
Star A emits light with a wavelength of peak emission two times the wavelength of peak emission of Star B. How does the total light emission per unit area (flux) compare for the two stars?
Star B emits 16 times more light per unit area as compared to Star A.
Star A appears very red, and is known to have a surface temperature of 3000 K. Star B appears blue-white, and is known to have a surface temperature of 24,000 K. What can we say about the amount of red light emitted by the two stars per unit surface area?
Star B emits more red light than Star A, even though star A appears redder than star B.
Which of the following is NOT a method used to determine the distances to galaxies?
Stellar parallax.
What can we learn from the spectrum of a star?
Temperature, composition, and motion towards or away from us
Given what we have learned, which of the possible fates of the Universe do you like the best (most likely, most appealling, etc)? Note: there is no right answers, just thought-provoking discussion expected. :-)
The "Great Attractor" is the theory I am most interested in. After doing more research and reading plenty of articles it became my favorite theory. It is interesting to me to think about some massive force out there that is pulling everything closer and nearer to it. As I read more articles about this theory it was put into very good perspective. One article had this quote "The only force that acts over such immense distance scales and through cosmic periods of time is gravity, so whatever it is, it's massive and unrelenting." I think what fascinates me the most about this theory is just the mystery behind it. This "Great Attractor" is not necessarily a thing but it is more of a focal point of our patch of the universe.
What differentiates an Sb galaxy from an E0 galaxy?
The 'S' refers to spiral, while the 'E' refers to elliptical.
How is the 'color index' of a star defined?
The 'color index' of a star is defined by determining the magnitude of the star in two colors (i.e. measuring blue light and red light) and subtracting the redder light's magnitude from the bluer light's magnitude.
A star of magnitude +4 compares to a star of magnitude +5 how?
The +4 star is 2.5 times brighter than the +5 star
How does the angular resolution of a 3 meter telescope compare to the angular resolution of a 1 meter telescope?
The 3 meter telescope has an angular resolution 3 times better, meaning that it can distinguish between objects 1/3 the distance apart compared to the 1 meter telescope.
Two people on a frozen pond are blown by the same wind (therefore assume the same force is applied to each person). One person masses 60 kg, while the other masses 80 kg. How does the acceleration of the two people compare? Assume there is no friction with the ice.
The 60 kg person accelerates at a rate 1.33 times that of the 80 kg. person.
How much brighter (energy produced per second, or flux) is an object at 6000 K than an object at 2000 K? Assume both objects are the same size.
The 6000 K object is 81 times as bright as the 2000 K object.
What is the main fusion process in a 30 solar mass main sequence star, and why?
The CNO cycle of fusion of hydrogen to helium. This dominates because the core of a high-mass star is extremely hot, much hotter than the core of the Sun. This makes the CNO cycle run much faster and be the main fusion process.
What is the dominant fusion process in a 10 solar mass main sequence star, and why?
The CNO cycle of fusion of hydrogen to helium. This dominates due to the much higher temperatures in the core of the more massive star, which makes the CNO cycle happen at a much higher rate than the proton-proton chain fusion cycle.
What differentiates an E0 galaxy from an E7 galaxy?
The E0 galaxy appears nearly circular on the sky, while the E7 galaxy appears quite elongated.
In a science experiment, you compute the force of gravity between two objects (A & B) with defined masses and spaced with their centers of mass a fixed distance apart. What would happen to the gravitational force if you cut the mass of object A in half without changing its center of mass location?
The Force of Gravity equation is F(g) = G * M1 * M2 / d2. So, if we double the first mass while leaving everything else unchanged, the force must double. You can see this as follows (this is a good way to approach these problems): Let M1 = M2 = d = 1. Now solve for the force of gravity F(g). You will get F(g) = G. (G is the gravitational constant, we won't need to know what it is to get the answer). Now cut M1 in half (i.e. divide the mass of object A by 2). Now M1=0.5, M2=d=1. Plug these in to the force of gravity equation, you will get F(g) = G * 0.5, which is half of what it was before we cut the first mass.
Discuss the following two questions about H-R Diagrams:
The H-R diagram tells us how a stars luminosity and its temperature are related. I believe the 72 nearest stars are common stars with their size, temperature, and luminosity. The other 21 brightest stars are less common since there is a lot less of those stars they are spread out through space in different sections as shown in the diagram. Such as Red Giants, Red Super giants, Blue giants. The different stars are put into different categories on the H-R diagram based on their different properties. Stars in the upper right corner are much larger and brighter than ones that are in the lower left corner which are much smaller and less bright. The larger stars emit much more light than smaller ones.
How does the structure (in terms of energy transport) of an M-class star compare to the Sun?
The M-class star is fully convective, which means it transports energy from the core to the surface only by convection (bulk motion of matter carrying energy).
How does the structure of an M5 spectral type star differ from the structure of the Sun (if at all)?
The M5 star is fully convective, which means it transports energy from the core to the surface only by convection (bulk motion of matter carrying energy).
What differentiates an Sa galaxy from an Sc galaxy?
The Sa galaxy has a large core in comparison to its disk versus the Sc galaxy having a small core in comparison to its disk.
What differentiates an Sb galaxy from an SBb galaxy?
The Sb galaxy has a round core, whie the SBb galaxy has a elongated straight feature across its core.
In what ways does the Sun interact with the Earth?
The Sun interacts with the Earth by sunlight, solar wind (producing the aurorae through the interaction of charged particles from the Sun hitting our atmosphere) and gravity (keeping the Earth in orbit).
How (at the atomic level) is the light seen in the above spectrum generated?
The above spectrum looks as it is from Argon with the red green blue and violet light generated. These lights are generated by an atom containing one or more electron orbiting a nucleus cell. In different elements only some orbits are allowed and specific amount of energy when an electron jumps from one orbit to another.
Two similar stars have the same surface temperature and are not moving with respect to us, yet one appears considerably bluer than the other as seen from Earth. How is this possible?
The bluer star is seen in clear space, while the redder star is behind an interstellar dust cloud, which absorbs some of the blue light.
Why does carbon fusion not happen in a one solar-mass evolving star?
The carbon never becomes hot enough to overcome the repulsive forces between the atoms, therefore it cannot fuse.
What two things will happen to an interstellar dust/gas cloud when a supernova explodes nearby?
The cloud will be enriched in heavy elements by the materials ejected by the supernova, and the cloud will begin to collapse due to the shockwave from the explosion.
A light source emits only a specific color of green light. If the source is moving towards you, how will the apparent color of the light change (if at all)?
The color will shift towards the blue.
What effect does the change to degeneracy in the core of a star have on the future evolution of that star?
The degenerate core supplies an additional electron-degeneracy pressure to balance gravity, so the lack of energy production in the core is no longer a factor in the size of the core.
What event sets the final mass of a forming star during the process of star formation?
The development of strong winds from the forming star halts the flow of material onto the core, which fixes the mass of the soon-to-be star.
Which of the following is the shortest/smallest distance?
The diameter of the Earth.
Which of the following is a neutron star?
The earth-sized object is a white dwarf, the single point is a black hole. Neutron stars are degenerate neutrons,degenerate carbon forms a white dwarf.
Which of the following is NOT a reason that modern research telescopes are always reflectors?
The effects of the passage of light through glass
An emission spectrum is given off by which of the following situations?
The emission spectrum is produced when electrons are able to fall from high energy levels to lower ones, thus giving off energy (photons). The hot thin gas is the setup for which this happens, as the gas much be hot for the electrons to be in higher energy levels. In the hot, dense gas, collisions and particle motion result in emission of all colors of light (continuum spectrum), while the cool gas with light passing through it yields the absorption spectrum, as the electrons in the low energy levels (in the cool gas) absorb photons and move to higher energies.
If the mass of a black hole doubles, how does the event horizon radius change? (Hint: consider the escape velocity equation)
The event horizon radius doubles.
As an object gets hotter, what happens to its brightness per unit surface area (flux)?
The flux increases rapidly as the temperature increases.
One box masses 300 kg., while a second box masses 75 kg. The boxes are pushed so as to accelerate at the same rate. Neglecting friction, how do the forces compare?
The force on the 300 kg box is 4 times the force on the 75 kg box.
Iron does not fuse normally in nature. Why is this?
The fusion of iron with any other element does not give off energy.
In astronomy, what does the 'Milky Way' refer to?
The galaxy of stars in which the Sun is located.
A star is observed to have hydrogen absorption lines in its spectrum. Astronomers determine that the star is moving towards us at a rate of 320 km/s. How do they know?
The hydrogen lines are all observed to be shifted slightly towards bluer wavelengths than they should be due to the Doppler effect.
Why doesn't all the hydrogen in the Sun (and elsewhere) fuse into helium instantly?
The hydrogen nuclei must be moving fast enough to overcome the repulsive effects of the charge and get close enough for fusion to take place, therefore only in very hot regions will fusion occur.
What powers the aurorae (northern lights) see in the atmosphere of the Earth?
The impact of high-energy particles from the Sun on the Earth's atmosphere as guided by Earth's magnetic field.
How does the light-gathering power of a 2-meter telescope compare to that of a 0.5-meter telescope?
The light-gathering power of the 2-meter telescope is 16 times that of the 0.5-meter telescope.
The most luminous standard candle is a Type Ia supernova. If two such supernovae are observed at their peak brightness, and one has an apparent magnitude of m = +23 and the other has an apparent magnitude of m = +27, which one is further away?
The m = +23 supernova is further away.
How does the brightness of a star of magnitude +8 compare to a star of magnitude +3?
The magnitude +3 star is 100 times brighter than the magnitude +8 star
The B magnitude of a star refers to what?
The magnitude of the star in only blue light
Which part (i.e. what color) of the metal bar pictured is hottest? Explain how you know this based on specific principles of light as discussed in class. [2 points]
The middle part of the metal bar the one that is glowing the brightest is the hottest part of the metal. We know this because we can translate what we learned with stars that the brighter the star the lower the B-V color index and therefore the hotter the star is.
An object begins at a temperature of 3,000K. If we were to double the temperature, what is the new wavelength of peak emission (as compared to the old)?
The new wavelength of peak emission must be 1/2 that of the old wavelength of peak emission.
Fundamentally, what causes the emission/absorption of light by individual atoms?
The nucleus has no significant interaction with light. Only the electrons typically emit/absorb photons, and then only at the allowed energies determined by the allowed electron energy levels as set by the atomic structure.
If nothing pushes or pulls on an object, how does its motion change (if at all)? Assume that the object begins in motion relative to the observer.
The object will continue moving in the same way it was.
What is important about Cepheid variable stars which makes them important to astronomers?
The period of variation in brightness is directly related to the luminosity of the star, making them useful as standard candles.
Which photon has more energy: one emitted by an electron dropping from the 4th energy level to the 1st energy level(ground state) or one emitted by an electron dropping from the 2nd energy level to the 1st energy level?
The photon emitted by an electron dropping from the 4th energy level to the 1st energy level(ground state).
A photon of red light (of a specific color) has a wavelength of 600 nanometers(nm), 1.5 times the wavelength (400 nm) of a photon of a specific color of blue light. How do the energies of the two types of light compare?
The photon of blue light has 1.5 times the energy that the photon of red light contains.
What is the specific, complete fusion process which powers the Sun?
The proton-proton chain, in which 6 hydrogen nucleii are fused through a process resulting in a helium nucleus and 2 hydrogen nucleii.
The Sun is radiating energy into space all the time in the form of light. Any hot object will cool down over time unless the energy is replaced, so what replaces the lost energy from the Sun?
The release of energy due to nuclear fusion in the core of the Sun.
A police car is driving towards you with its siren sounding. As it passes you, how (if at all) does the sound change?
The siren drops to a lower pitch.
What do we mean if we say that a star has a B-R color index of -1.0?
The star is emitting 2.5 times more blue light than red light.
You see a star that appears red to your eye. What does this say about the relative amount of light of various colors (e.g. red, yellow, blue) produced by the star?
The star produces light of all colors, but produces more red light than any other color.
Which of the following observations about a star forms the basis for our classification of that star?
The strength (or absence) of specific absorption lines in comparison to each other as determined by the temperature of the star.
A child pushes on a swing with a force of 10 N. With what force (and in which direction) does the swing push on the child?
The swing pushes on the child with a force of 10 N in the opposite direction that the child is pushing.
What is the significance of the helium core becoming degenerate in a one solar-mass evolving star?
The switch to degeneracy in the helium core allows the core of the star to stop collapsing since electron degeneracy supplies a new outward pressure to balance gravity.
An object has a wavelength of peak emission of 10,000 nm. Which of the following statements is correct?
The temperature of the object is 290K, or 17C (i.e. ~room temperature)
Classification of stars is currently based on which of the following?
The temperature of the star as revealed by the presence or absence of absorption lines.
What would happen if two white dwarf stars of 0.5 solar masses collided?
The two objects would combine into a 1.0 solar-mass white dwarf.
Consider two stars, each with a mass of 3 solar masses, that are separated by a distance of 8 AU. Which of the following situations results in a stronger gravitational force between the two stars than the situation above?
The two stars (still of 3 solar masses each), are separated by a distance of 4 AU.
Object A is twice as hot as object B. How does the wavelength of peak emission of object A compare (numerically) to that of object B?
The wavelength of peak emission of object A is 1/2 the wavelength of peak emission of object B.
Object A is three times as hot as object B. How does the wavelength of peak emission (i.e. wavelength of the peak of the emission curve) of object A compare to that of object B?
The wavelength of peak emission of object A is 3 times that of the wavelength of peak emission of object B.
As seen in the OpenOffice assignments, what is the relationship between absolute magnitude and (B-V) color index for stars, if any?
There is a very good relationship between absolute magnitude and color index, stars of dimmer (higher) magnitude essentially always have a higher color index.
The light from a bright object is different from the light from a dim object in what way?
There is more energy (more photons) coming from the bright object.
As seen in the OpenOffice assignments, how is the apparent magnitude of a star is related to the (B-V) color index (or is it)?
There is no relationship between apparent magnitude and color index, stars of the same color index can be of very different apparent magnitudes.
What is the energy source for a white dwarf star?
Thermal energy (heat) stored within the star.
In a universe where helium fusion were not normally possible (as is the case for iron in reality), what would be the final state of one solar-mass stars?
These stars would end with a degenerate core of helium, possibly surrounded by a layer of hydrogen which never reached fusion temperature.
Why are type Ia supernovae useful as standard candles?
They all are triggered by a white dwarf crossing 1.44 solar masses, so the explosions are virtually the same.
What is the root cause of stars not existing as main sequence stars forever?
They all run out of hydrogen in the region above 10 million Kelvin, so they lose their energy source.
What is common across all the stars located on the main sequence (running roughly from Star W to star Z)?
They are fusing hydrogen to helium in their core.
What is the difference between visible light and radio waves?
They have different wavelengths (radio being longer) but are both types of light.
The pink glow in the central region of this image is generated by what astronomical material? If we were to take a spectrum of that material, what type of spectrum (absorption, emission, continuum) would it be?
This is interstellar reddening that is caused when dust absorbs blue light more easily than red light and this is what causes this to happen. We know this gas and dust exist because of optical emission lines which is produces by hot hydrogen, radio emission produced by cold gas. We are looking at a nebula, the pink glow is generated by hot interstellar hydrogen. A spectrum of the pink area would show a hydrogen emission-line spectrum.
How do we detect the presence of black holes?
Through detection of the effects of the black hole's gravity on passing light.
How do we detect the presence of dark matter in the Galaxy?
Through its gravitational influence of stellar orbit speeds as seen on rotation curves.
What is the main function of a telescope?
To gather together light from a large area to a focus in a small area for detection.
What is the purpose of a telescope?
To gather together light from a large area to a focus in a small area for detection.
In which cluster type would we expect to find Type 1a and Type II supernovae?
Type Ia would occur only in globular clusters, while Type II would occur only in open clusters.
The star Polaris (the North Star) has a magnitude of 2.0. How much brighter than Polaris is the star Vega?
Vega is 6.25 times brighter than Polaris.
How can you change the velocity of your car without changing its speed?
Velocity is speed with direction, speed is just how fast you are moving. Changing either speed or direction would change ones velocity. So one could maintain the same speed and just change its direction which would change the cars velocity.
Assume that the star Vulcan is similar in all ways to the star Vega, but has an apparent magnitude of +5. How far is Vulcan away from the Sun (assume Vega is 10 pc from the Sun)?
Vulcan is at a distance of 100 parsecs from the Sun.
Which of the following stars could be an O-class main-sequence star?
W
Wave A has a wavelength 5 times that of wave B, but both move at the same speed. How does the frequency of Wave A compare to the frequency of wave B?
Wave A has a frequency 1/5th that of Wave B.
Referring to the H-R diagram above, what is the physical reasoning behind our ability to know that Star X must be much larger than star Y? Your explanation should be based on the physical properties of the star as shown on the graph, NOT simply the location on the graph.
We know from previous work that Star x is in the red giant club. We can see this by noticing that red giants are large, cooler, and highly luminous. We can see this corresponds on the H-R diagram. cooler, so less bright per unit surface, but brighter, so therefore needs more surface area to be that bright.
If the circular velocity for an orbit around the Earth at the surface is 8 km/s, what will the circular velocity for an orbit around the Earth at a distance of 4 Earth radii from the Earth's center?
We will use the circular velocity formula for this problem: v(circ) = (G*M/d)0.5. *Note: raising a number to the 0.5 power is equivalent to taking the square root, so 40.5 = 2. Now, what we know is: v(at d=1 earth radius) = 8, d = 1 (earth radius). So 8=(G*M/1)0.5=(G*M)0.5. Now at a distance of 4 earth radii: d=4. So v(at d=4 earth radii)=(G*M/4)0.5=(G*M)0.5/(4)0.5. [*This is mathematically equivalent and does not violate order of operations]. We know from before that (G*M)0.5 = 8, so: V(at d=4 earth radii) = 8/40.5 = 8/2 = 4 km/s. Basic approach used here is to use what we know (distance and speed at d=1 earth radius) to get a simple way to write the part of the formula that doesn't change from one case to the other (in this case the (G*M)0.5 part) so we don't need to actually know what the individual numbers are.
Do individual low-mass stars (1 solar mass or below) return significant amounts of heavy elements such as carbon and oxygen to the interstellar medium? Explain your reasoning.
We would expect to see very little moment in an H-R diagram with these kinds of stars. They are slow burning and have long life times. They are in the main sequence the longest. In the final phase of this mass star it will shed its outer layer as a planetary nebula and leave behind a white dwarf. The composition of this star in this phase is 75% hydrogen and 25% helium and it has very small amounts of heavier elements. Low-mass stars do not contribute to an increase in the amount of heavy elements to the interstellar medium. The lowest-mass stars never fuse materials beyond helium, and anyway have not have enough time to evolve off the main sequence. Slightly higher-mass stars (like the Sun) do form carbon and oxygen in their cores, but that material mainly remains trapped in the white dwarf remnant and thus is not returned to the ISM.
When does hydrogen fusion completely stop in a one solar-mass star?
When the star has blown off its outer envelope as a planetary nebula. The remaining remants of hydrogen, now exposed to space, will never get hot enough to fuse.
The above image is of a portion of the surface of the Sun. What physical property of the gases in the central region makes them appear dark as compared to the surrounding gas?
Why is the gas dark? [It is cooler due to the interrupted convection.]
Which star is a white dwarf?
Y
Which star will have the highest absolute magnitude?
Y
On the above diagram, which star location is most likely to correspond to an M5 main sequence star?
Z
Which of the following will become a cataclysmic variable system?
a close binary pair of ~1 solar-mass stars.
Which of the following correctly fills in the blank in the following statement: "A more-massive main sequence star must have ___________________ than a lower-mass main sequence star. "
a higher temperature, larger size, and higher luminosity
A certain engine can exert 150,000 kg m/sec/sec of force. Assuming that all the force is used to accelerate the vehicle on which the engine is mounted, how fast will the vehicle accelerate assuming that it masses 5,000 kg? Neglect friction/air resistance
a=30 m/s/s
The source of the periodic pulses of light observed from a pulsar is:
beams of radiation radiating away from the magnetic poles of a spinning neutron star sweep across space.
What causes the pulses we observe from a pulsar?
beams of radiation radiating away from the magnetic poles of a spinning neutron star sweep across space.
Photons of which color of light carry the most energy?
blue
In comparison to a cooler object, a hotter object will appear:
brighter and bluer.
A red giant star (first red giant phase) of one solar mass is _____ and ______ than the Sun.
cooler, brighter
Which of the following properly lists the fusion reactions and locations taking place in a horizontal branch star?
core helium fusion, shell hydrogen fusion.
For the next 4 questions covering your conceptual understanding of some of the math relations covered to date, assume that any parameter not specifically mentioned is held constant. If the wavelength of light increases, the frequency __________.
decreases.
If a star's magnitude changes from +0.7 to +1.2, the star's magnitude had increased, so the star:
gets dimmer
If a star gets dimmer by decreasing its energy output (luminosity, or total photons generated per second), its absolute magnitude __________. incr
increases.
If the distance to a light source decreases, the apparent brightness (photons per second observed) of the light source ____________.
increases.
If the temperature of an object increases, the amount of light generated by that object ________.
increases.
What is the last fusion product in a high-mass star (i.e. where does the fusion sequence stop)?
iron
Which of the following is NOT something that we can learn about a star by taking a spectrum?
mass
Give an example of a NON-scientific question and explain (based on the definitions in the class notes) why that the question is not scientific. Tip: pick a specific aspect of the definition and write a question that is in violation of that part of the definition. [2 points]
ow was the universe formed? This is a non scientific question, we can form a hypothesis about how the earth was formed but we can test it. There would be no way to text our hypothesis because we would have to use the way we though the universe was formed and try to form another one. This is not possible. This directly violates what is a scientific question because our hypothesis is neither testable nor disprovable. No expirment that we could create here on earth would be able to validate our hypothesis so this can not be a scientific question.
Which color of light has the longest wavelength?
red
A spacecraft is in a circular orbit of radius 50,000 km around an asteroid (A), and has an orbital speed of 5 meters/second. A similar spacecraft is in a circular orbit or radius 50,000 km around another asteroid (B), but is moving at 10 meters/second. How do the masses of the two asteroids compare?
so the mass of asteroid B is 4 times the mass of asteroid A
A pattern of emission lines is observed to have two yellowish lines in close proximity and no other light at all. Looking at the slide 'Emission lines for other elements' in the first presentation for this week, what element is emitting this light?
sodium.
A light year is ____________.
the distance light travels in one year.
Spectra of two stars are aquired. The first emits most of its light in the ultraviolet (wavelength of peak emission = 200 nm) while the second emits most of its light as visible light (wavelength of peak emission = 500 nm). From this information we can conclude ___________.
the first star is hotter.
What is the composition of the materials blown off a one solar-mass star during the planetary nebula phase?
~75% hydrogen, ~25% helium, and small amounts of heavier elements.
