Stellar Astronomy - Test One
Kepler's second law of planetary motion
states that a line joining a planet and the Sun sweeps out equal amounts of area in equal intervals of time.
The electromagnetic spectrum of light can also be arranged in terms of wavelengths. Which of the following has the longest wavelength? visible light radio waves microwaves x-rays infrared light ultraviolet light gamma rays
radio waves have the lowest frequency and the longest wavelength
Consider a planet orbiting the Sun. If the mass of the planet doubled but the planet stayed at the same orbital distance, then the planet would take
the same amount of time to orbit the Sun.
Which of the following travels the slowest? A.radio waves B.visible light C.x-rays D.infrared light E.they all travel at the same speed
they all travel at the same speed
Which of the following types of light travels at the fastest speed? visible light radio waves microwaves x-rays infrared light ultraviolet light gamma rays
they all travel at the same speed
If a star existed that was only a hot, dense core and did NOT have a low-density atmosphere surrounding it, what type of spectrum would you expect this particular star to give off?
Continuous Spectrum
What type of spectrum is produced when the light emitted directly from a hot, dense object passes through a prism?
Continuous Spectrum
Energy is released from atoms in the form of light when electrons A.move from high energy levels to low energy levels. B.move in their orbit around the nucleus. C.move from low energy levels to high energy levels. D.are emitted by the atom. E.are absorbed by atoms.
D.are emitted by the atom.
The energy of a photon emitted by thermonuclear processes in the core of the Sun takes thousands of years to emerge from the surface because: A.it is circling the gravitational field of the Sun B.it loses energy due to convection, conduction, and radiation C.of the Sun's enormous radius D.it is absorbed and re-emitted countless times along the way
D.it is absorbed and re-emitted countless times along the way
Imagine that you are observing the light from a distant star that was located in a galaxy 100 million LY away from you. By analysis of the starlight received, you are able to tell that the image we see is of a 10 million year old star. You are also able to predict that the star will have a total lifetime of 50 million years, at which point it will end in a catastrophic supernova. How old does the star appear to be to us on Earth? How ling will it be before we receive the light from the supernova event? Has the supernova already occurred? If so, when did it occur?
10 Million LY 40 Million LY Yes. 60 Million LY ago.
3. What was the greatest amount of time that it took for any one of the pictures to travel from the child to you?
11.4 ly
Betelgeuse is a red star in the constellation Orion. Rigel is a blue star in the same constellation. If they were at the same distance, Betelgeuse would be brighter than Rigel. Explain how this info implies that Betelgeuse is larger in size than Rigel.
A blue star burns hotter than a red star making it more bright but it is still dimmer than this red star, so the blue star has to be smaller , otherwise it would be brighter than the red star.
Imagine that you observe the Sun while in your spaceprobe far above Earth's atmosphere. Which of the following spectra would you observe by analyzing the sunlight? A.dark line absorption spectrum B.bright line emission spectrum C.continuous spectrum
A.dark line absorption spectrum
Which of the following spectra is produced by the Sun? A.dark line absorption spectrum B.bright line emission spectrum C.continuous spectrum
A.dark line absorption spectrum
The energy emitted by the Sun is produced: A.in a relatively small region at the very center of the Sun B.uniformly throughout the whole Sun C.throughout the whole Sun, but more in the center than at the surface
A.in a relatively small region at the very center of the Sun
Stars like our Sun have low-density, gaseous atmospheres surrounding their hot, dense cores. If you were looking at the spectra of light coming from the Sun (or any star), which of the three types of spectrum would be observed?
Absorption because it passes through cool gas.
A solid, glowing-hot object will emit light over the full range of wavelengths resulting in a continuous spectrum. If a diffuse and relatively cool cloud of gas is located between the glowing, hot object and an observer, what type of spectrum will the observer detect coming out of the cloud? a) continuous spectrum b) absorption spectrum c) emission spectrum
Absorption spectrum, because the gas absorbs some of the photons.
Use: slow, fast, accelerating, slowing down At C, the planet is going ________, and at A it is going _______, which means that in D, it is _________, and at B it is _________.
At C, the planet is going fast, and at A it is going slow, which means that in D, it is slowing down, and at B it is accelerating.
In which case does an atom emit more energy? A) An electron drops down from the first excited state to the ground state. B) An electron drops down from the third excited state to the ground state.
B, because more energy is released
Sunspots appear dark because they are: A.Holes in the photosphere through which you can see deeply into the stellar interior B.A bit cooler and thus dimmer than the rest of the photosphere C.Large opaque structures that block light from the glowing solar surface D.Causing retinal damage
B.A bit cooler and thus dimmer than the rest of the photosphere
The temperature of the layer of gas from which visible light is emitted from the Sun is: A.a few hundred degrees K B.a few thousand degrees K C.a few million degrees K D.several hundred million degrees K
B.a few thousand degrees K
The Hubble Space Telescope has revolutionized astronomy with its 2.4 meter mirror. This achievement is due to its significantly better _______________ compared to Earth-based telescopes.
B.magnifying power
If Betelgeuse and Rigel were at the same distance, which one would be larger?
Betelgeuse
The diameter of each of the two Keck telescopes in Hawaii is 10 m. Hubble Space Telescope has a 2.4 meter mirror. Which of the following statements is correct: A.Hubble has more light gathering power because it is in space B.The light gathering power of each Keck telescope is about 16 times more than that of Hubble C.The Keck telescopes have more magnification than Hubble because they have much larger mirrors
C.The Keck telescopes have more magnification than Hubble because they have much larger mirrors
Which of the following would be true about comparing gamma rays and radio waves? A.The radio waves would have a lower energy and would travel slower than gamma rays. B.The gamma rays would have a shorter wavelength and a lower energy than radio waves. C.The radio waves would have a longer wavelength and travel the same speed as gamma rays. D.The gamma rays would have a higher energy and would travel faster than radio waves. E.The radio waves would have a shorter wavelength and higher energy than gamma rays.
C.The radio waves would have a longer wavelength and travel the same speed as gamma rays.
How would sunspots appear if you could magically remove them from the Sun? A.They would appear blue-white, like Sirius but brighter. B.Because sunspots are dark spots, they would be invisible against the blackness of space. C.They would shine bright orange in color, like Arcturus. D.They would not appear any differently than on the surface of the Sun. E.They would shine only with reflected sunlight, appearing similar to Venus.
C.They would shine bright orange in color, like Arcturus.
You overhear a student saying: "one light year is equal to the time it takes light to travel from the Sun to the Earth. Do you agree or disagree? Explain your reasoning.
Disagree, because one light year is equal to the time it takes light to travel in one year.
What type of spectrum is produced when the light emitted directly from a hot, low-density cloud of gas passes through a prism?
Emission Spectrum
Imagine that you are looking at a neon sign in a store window that says "OPEN." This sign can be thought of as a tube filled with a gas of neon atoms that have electrons changing from one energy state to a different energy state and in the process are giving off mostly red light. Which type of spectrum would you observe coming from the "OPEN" sign? a) continuous spectrum b) absorption spectrum c) emission spectrum
Emission spectrum, because only gas gives off light.
Of all the types of light the Sun gives off, it emits the greatest amount of light at visible light wavelengths. If the Sun were to cool off dramatically and as a result start giving off mainly light at wavelengths longer than visible light, how would the frequency, energy, and speed of this light given off by the sun also be different?
Frequency = less Energy = less Speed = same
Sun's Interior
Gravity pulls inward gas Pressure pushes outward
Describe in detail the source of light and the path the light must take to produce an absorption spectrum.
Hot, dense energy source, passes through a cool, low-density cloud
You are shown an image taken of the Andromeda Galaxy, which is located about 2.5 million LY away from us. Is this an image showing how the Andromeda Galaxy looks right now, how it looked in the past, or how it will look in the future? Explain.
How it looked in the past. We are seeing it as it was 2.5 million LY's ago.
Two students are looking at a brightly lit full Moon, illuminated by reflected light from the Sun. Consider the following discussion between the two students about what the spectrum of moonlight would look like. Student 1: I think moonlight is just reflected sunlight, so we will see the Sun's absorption line spectrum. Student 2: I disagree. An absorption spectrum has to come from a hot, dense object. Since the Moon is not a hot, dense object, it can't give off an absorption line spectrum.
I agree with Student 1 because the Moon is dense and doesn't have an atmosphere.
Student 1: I think that all you need to do to get signs to give off light of different colors is to use tinted glass of different colors. If you electrify a gas, white light is emitted so the color of glass gives the sign its color. Student 2: That can't be it because the electrons will always move between the same energy levels for atoms in a neon sign and so the will mostly give off red light. I think the yellow sign is filled with a different type of atoms with energy levels that are farther apart, so when the electrons drop down from a higher energy level to a lower energy level, the atoms will give off yellow light instead of red light.
I agree with Student 2 because different gases will give off different light.
Scientific theories do not have to be
Perfect
Which of Galileo's observations disproved the Ptolemaic (geocentric) model?
Phases of Venus
There are dark lines in the absorption spectrum that represent missing light. What happened to this light that is missing in the absorption line spectrum?
It was absorbed
4. If each child was 12 years old when he or she sent his or her picture to you, how old was each of the children when you received their picture? Jon _______ Peter _______ Celeste _______ Savannah _______ Inga _______ Ron _______
Jon 21.5 Peter 18 Celeste 20.6 Savannah 16.3 Inga 22.8 Ron 23.4
Which of the following best describes what would happen if Mercury and Jupiter were to switch places in their orbits about the Sun?
Jupiter, the larger planet, would have a shorter orbital period than before.
How are wavelength, frequency, and energy related to photons of light?
Longer wavelength means lower frequency and lower energy
2. Which child lives closest to the Sun? How far away does he or she live?
Savannah. Lives 4.3 ly from the sun
Which of the following would cause the force on the Moon by Earth to increase by the largest amount?
Move the Moon two times closer to Earth.
Will an atom emit light if all of the atom's electrons are in the ground state?
No, because it doesn't have any energy to give.
6. Imagine that the six pictures were broadcast by satellite to you and that they arrived at exactly the same time. For this to be true, does that mean that all of the children sent their pictures at the same time? If not, which child sent his or her picture first and which child sent his or her picture last?
No, the children did not send their pictures at the same time. The child farthest sent their picture first. The child closest sent their picture last.
During how many portions of the planet's orbit (A, B, C and D) would the planet be speeding up the entire time?
Only during one of the portions shown. Portion B.
Kepler's second law says "a line joining a planet and the Sun sweeps out equal areas in equal amounts of time." Which of the following statements means nearly the same thing?
Planets move farther in each unit of time when they are closer to the Sun.
Briefly explain the main differences between Ptolemy's and Copernicus' models of the solar system.
Ptolemy had the Earth as the center of the solar system, while Copernicus had the Sun. They both had perfectly circular orbits for the planets. Copernicus' model was not immediately accepted because it was less accurate at predicting compared to Ptolemy's.
The visible light portion of the electromagnetic spectrum of light is often subdivided into the colors of red, orange, yellow, green, blue, indigo, and violet. Using the words greatest, least, highest, lowest, fastest, slowest, longest, and shortest, write a sentence or two that describes how light at the red end of the visible portion of the spectrum and light at the violet end of the visible portion of the spectrum compare in terms of their energy, frequency, speed, and wavelength.
Red has the lowest frequency, while violet has the highest. Red has the longest wavelength, while violet has the shortest.
Imagine that you have received six pictures of six different children who live near some of the closest stars to the Sun. Each picture shows a child on his or her 12th birthday. The pictures were each broadcast directly to you (using a satellite) on the day of the child's birthday. Notes the abbreviation "ly" is used below to represent a light-year. John lives on a planet orbiting Ross 154, which is 9.5 ly from our Sun. Peter lives on a planet orbiting Barnard's Star, which is 6.0 ly from our Sun. Celeste lives on a planet orbiting Sirius, which is 8.6 ly from our Sun. Savannah lives on a planet orbiting Alpha Centauri, which is 4.3 ly from our Sun. Inga lives on a planet orbiting Epsilon Eridani, which is 10.8 ly from our Sun. Ron lives on a planet orbiting Procyon, which is 11.4 ly form our Sun.
See questions 1 - 6
Imagine that you are looking at two different spectra of the Sun. Spectrum #1 is obtained using a telescope that is in high orbit far above Earth's atmosphere. Spectrum #2 is obtained using a telescope located on the surface of Earth. Label each spectrum as either Spectrum #1 or Spectrum #2.
Spectrum 1 has no atmosphere Spectrum 2 has an atmosphere
The graph shows the blackbody spectra for three different stars. Which of the stars is at the highest temperature?
Star A
Light and Atoms
Student 2's Drawing is the correct one
What do Kepler's Laws tell us about the orbits (shapes and speeds) of the planets?
The orbits are elliptical rather than perfectly circular and the closer to the sun, the faster the speed of the planet's orbit.
Complete the following sentence describing the relationship between the energy, frequency, and wavelength of light, using the words highest, lowest, longest, and/or shortest.
The portion of the electromagnetic spectrum of light with the greatest energy has the HIGHEST frequency and the SHORTEST wavelengths
In what direction would the net (total) force point if a space probe were moving very quickly toward the Moon when at Position B (midway between Earth and Moon)?
Toward Earth
Of all the types of light the Sun gives off, it emits the greatest amount of light at visible light wavelengths. If the sun were to cool off dramatically and as a result start giving off mainly infrared radiation, how would the wavelength, frequency, energy, and speed of this light given off by the Sun also be different?
Wavelength: longer Frequency: lower Energy: lower Speed: same
5. Is there a relationship between the current age of each child and his or her distance away from Earth? If so, describe the relationship.
Yes, there is a relationship. The child farthest away, their picture would take the longest to get to us, so they would be the oldest compared to the other children.
The Orion Nebula is a hot, thin cloud of glowing gas, so its spectrum is
a few bright lines against a dark background
1. Describe in detail what a light-year is. Is it an interval of time, a measure of length, an indication of speed, or some other quantity?
a measure of length
For each statement provided, choose the word that correctly describes how the two forms of light compare. a) infrared light greater/less energy than ultraviolet light b) x-ray photons have longer/shorter wavelengths than gamma ray photons c) visible electromagnetic radiation has a higher/lower frequency than radio wave electromagnetic radiation d) infrared light has a faster/slower/same speed than microwave light
a) infrared light less energy than ultraviolet light b) x-ray photons have longer wavelengths than gamma ray photons c) visible electromagnetic radiation has a higher frequency than radio wave electromagnetic radiation d) infrared light has the same speed as microwave light
Imagine that you take images of two main sequence stars that have the same mass. From your observations, both stars appear to be the same age. Consider the following possible interpretations that could be made from your observations. a) Both stars are the same age and the same distance from you. b) Both stars are the same age but at different distances from you. c) The stars are actually different ages but at the same distance from you. d) The star that is closer to you is actually the older of the two stars. e) The star that is farther from you is actually the older of the two stars. How many of the five choices are possible? Explain.
all
Another property of light is the energy. Which of the following has the greatest energy? visible light radio waves microwaves x-rays infrared light ultraviolet light gamma rays
gamma rays
The electromagnetic spectrum of light is often arranged in terms of frequency. Which of the following has the highest frequency? visible light radio waves microwaves x-rays infrared light ultraviolet light gamma rays
gamma rays have the highest frequency and the shortest wavelength
What are constellations?
groups of stars making an apparent pattern in the sky
