Astronomy II - test I (practice questions + quizzes + test questions)
Describe the conditions that lead to each of the three basic types of spectra. Which type is the Sun's visible-light spectrum, and why?
A continuous spectrum is seen when we have a hot solid, liquid, or dense gas emitting light across a broad range of wavelengths. We see an emission line spectrum when we look at a cloud of thin (low density) gas because we see only the wavelengths of light that correspond to the atomic transitions allowed in that gas. We see an absorption line spectrum when we look at a hot object (like a star) through a thin cloud of gas. The continuous spectrum loses photons of the specific frequencies that the atoms in the thin gas like to absorb. The spectrum at the start of the chapter shows a continuous spectrum from the Sun's hot "surface." However, before the light reaches us, it passes through the Sun's thin atmosphere and photons of certain specific wavelengths are absorbed by the gas. This creates the dark lines in the spectrum.
What is a photon? In what way is a photon like a particle? In what way is like a wave?
A photon is a particle of light. Like particles, light has a smallest unit that cannot be subdivided. However, light also has wavelike properties, such as having characteristic wavelengths and frequencies.
How is a star's apparent brightness related to its luminosity? Explain the inverse square law for light.
A star's luminosity measures how much energy it radiates into space. The apparent brightness tells us how bright it seems in our sky. The two concepts differ because objects that are farther away appear dimmer. This relationship is described by the inverse square law for light, which says that the brightness of a star follows an inverse square law with distance, getting four times dimmer every time we move twice as far away.
Define atomic number and atomic mass number. Under what conditions are two atoms different isotopes of the same element? What is a molecule?
An atom's atomic number is the number of protons it has in its nucleus. Its atomic mass number is the number of protons plus the number of neutrons. Two atoms can have the same number of protons (have the same atomic number) and have different numbers of neutrons. In this case, we say that these atoms are different isotopes of the same element. A molecule is a group of two or more atoms bound together.
How does a camera record light? How are images affected by exposure time? What are pixels?
Cameras record light by focusing light through a lens onto a detector, usually a CCD. A shutter controls the exposure time; the longer the exposure time, the more light is collected. Pixels are the individual "picture elements" on the CCD; in principle, more pixels means better resolution. Each pixel counts the number of incoming photons it collects.
Draw a sketch of a Hertzsprung-Russell (H-R) diagram. Label the main sequence, giants, supergiants, and white dwarfs. Where on this diagram do we find stars that are cool and dim? Hot and dim? Hot and luminous?
Cool and dim stars would be in the lower right. Hot and dim stars would be in the lower left. Hot and luminous would be in the upper left.
How can we use emission and absorption lines to determine the chemical composition of a distant object?
Each atom tends to absorb and emit different wavelengths of light. Similarly, every molecule absorbs or emits different bands of wavelengths. So when we look at an absorption or emission spectrum, we can see the "fingerprints" of the different atoms (or ions) or molecules. In this way, we can learn what an object is made of without ever sampling the object.
List the different forms of light in order from lowest to highest energy. Is the order the same from lowest to highest frequency? From shortest to longest wavelength? Explain.
From lowest to highest energy, the electromagnetic spectrum runs: radio, infrared, visible, ultraviolet, X rays, gamma rays. This is the same order we would get if we listed them in order of frequency (lowest to highest) since energy is directly proportional to frequency. However, it is the reverse of what we get if we list them in order of wavelength, because frequency and wavelength are inversely related.
what do we mean by a star's luminosity class? Briefly explain how we classify stars by spectral type and luminosity class.
Luminosity classes of stars are designated by Roman numerals and tell us what region of the H-R diagram the star falls in. We use both spectral type and luminosity class (which are determined by looking at absorption lines in stars' spectra) to completely classify stars as the spectral type tells us the temperature while the luminosity class tells us the radius. So, for example, our Sun is a G2 V, where G2 is the spectral type (it says that it's a yellow-white star) and V is the luminosity class (it tells us that it is a main-sequence star).
What do we mean by a star's spectral type, and how is spectral type related to surface temperature and color?
Spectral types are a way of classifying stars according to what spectral lines we see in their spectra. The spectral types run OBAFGKM, where O stars have the hottest surface temperatures and M have the coolest. This is related to color (appears reddish or blueish), which can also be used to estimate the surface temperature, just not as precisely.
How do we use stellar parallax to determine a star's distance, and how can we then determine its luminosity?
Stellar parallax is the tiny change in position (RA, DEC) of stars in our sky due to Earth's motion around the Sun. Since more distant stars show smaller parallaxes than closer ones, we can measure the amount that stars move over 6 months (half of an Earth orbit) and find the distance to the stars. Once we know this, we can use the apparent brightness of the star along with the inverse square law for light to determine the star's luminosity.
What are the two key properties of a telescope, and why is each important?
Telescopes have two key properties: light-collecting area and angular resolution. One is light- collecting area. A telescope can collect a lot more light than the human eye can because it is larger. This is important because the objects astronomers want to look at are usually very faint. The other important property of telescopes is angular resolution: Telescopes can make out finer details than our eyes can. This is important because the objects we want to study appear small in our sky.
What are apparent and absolute magnitudes, and how are they related to apparent brightness and luminosity?
The apparent magnitude of a star is how bright it appears from here on Earth, measured on a special scale where a factor-of-100 increase in brightness corresponds to five magnitudes lower in value. The absolute magnitude is what the apparent magnitude would be if the star were at a distance of 10 parsecs. These two quantities are similar to the apparent brightness and luminosity; they are just measured on different scales, are computed using formulas with base 10 logarithms, and scale so that the smaller the magnitude, the brighter the star.
List at least three ways in which Earth's atmosphere can hinder astronomical observations. What problem can adaptive optics help with?
The atmosphere has three negative effects on observations. First, it blocks light of most wavelengths (UV, Xrays, etc.) from ever reaching the ground. Second, the atmosphere scatters human-generated light, creating light pollution that makes it more difficult to make observations. And finally, the constant movement of air in the atmosphere (the source of turbulence when flying) causes stars to appear to twinkle, which effectively blurs telescopic images. Adaptive optics is a technology that can essentially undo the blurring caused by twinkling. (Other problems could include clouds/weather, etc.)
How do reflecting telescopes differ from refracting telescopes? Which type is more commonly used by professional astronomers, and why?
The difference between a reflecting telescope and a refracting telescope lies in how the light is focused. In a refracting telescope, a lens is used to focus the light, whereas in a reflecting telescope we use mirrors. Today, we mainly use reflectors because they allow for larger mirrors.
How does your eye focus light? How is a glass lens similar? What do we mean by the focal plane of a lens?
The eye focuses light by bending (refracting) it so that rays of incoming light all meet up on the same point in the back of our eye. A glass lens does the same thing, but unlike the eye it cannot adjust its shape to change its focus. The focal plane of a lens is the place where an image appears in focus.
Describe how deeply each portion of the electromagnetic spectrum penetrates Earth's atmosphere. Based on your answers, why are space telescopes so important?
The only wavelengths that make it all the way to the ground are the narrow range of visible light (and a very small amount of the ultraviolet that is nearest in wavelength to visible light) and the radio wavelengths. A few other wavelengths can be detected from high mountains or from aircraft, but most wavelengths require us to put telescopes in space, which is why space-based astronomy is so important.
What are the three basic categories of astronomical observation, and how is each conducted?
The three basic types of observing are imaging, spectroscopy, and time monitoring. For imaging, the telescope functions like a camera, taking a picture of the object of interest. For spectroscopy, astronomers use a diffraction grating (or some other means) to spread the light into its component wavelengths and then measure the brightness of each wavelength. Finally, for time monitoring observations, astronomers use multiple images or otherwise measure the incoming light at known times to measure how the brightness varies.
What are the three basic of binary star systems? Why are eclipsing binaries so important to measuring masses of stars?
There are three kinds of binary star systems. The first is visual binaries, ones in which we can see both stars distinctly as they orbit each other. The second type of binary system is the eclipsing binary, which we see by examining the light curve. Light curves of eclipsing binaries show periodic dimming, corresponding to when one of the stars passes behind the other and its light is blocked. The final type of binary is the spectroscopic binary. For these systems, we detect the presence of two stars (rather than one) by the Doppler shifts in the spectral lines. Eclipsing binaries, which are also usually seen as spectroscopic binaries, are particularly important for finding stellar masses because we can measure the orbital periods of the stars and the velocities. (We can get the velocities in this case because we know that these systems orbit in the plane of our line of sight.) With this information, we can determine the orbital separation and then the masses via Newton's version of Kepler's third law.
Describe the phase changes of water as you heat it, starting from its solid phase, ice. What happens at very high temperatures? What is a plasma?
We begin with ice, water's solid form. In this state, the molecules of water are bound to their neighbors and cannot move significantly. As we heat it up (apply more energy), the molecules vibrate faster until they have so much energy that they break the bonds between themselves and their neighbors ("melting"). At this point, molecules can slip past each other and we have a liquid. In this state, the molecules are not directly bound to their neighbors, but they are attracted to each other enough to stay grouped together. As the liquid is heated further, the molecules move faster and faster. Eventually, even the attraction felt between molecules in the liquid state is not enough to overcome the molecules' random motions and the water becomes a gas ("evaporation"). In the gas state, the individual molecules fly about freely without feeling attractions to each other (although they do collide with each other). If we keep heating the water vapor, eventually we will give it so much energy that the molecules will break apart ("dissociation"), and we no longer have water, just hydrogen and oxygen (or, initially, H and OH ions). If we apply even more energy, the electrons will be removed from their atoms ("ionization"), and we will have a hot plasma, an electrically charged gas.
How do we convert a spectrum shown as a band of light (like a rainbow) into a graph of a spectrum?
We convert the rainbow-like spectrum into a graph by plotting the intensity (brightness) of the light at each wavelength as a function of the wavelength. This sort of graph is easier to interpret than the rainbow-like spectrum is.
Why do we say that light is an electromagnetic wave? Describe the relationship among wavelength, frequency, and speed for light.
We say that light is an electromagnetic wave because light is a vibration of electric and magnetic fields. Because all electromagnetic waves travel at the speed of light, the product of their frequencies and wavelengths is always the speed of light. (This is because the product of frequency and wavelength is always the speed of the wave. For light, that speed is constant.)
Atoms in a thin, hot gas emit light at: a. specific wavelengths, depending on the element b. all wavelengths, with the shape of the continuum distribution depending on the temperature of the gas c. only visible wavelengths
a
Compared to an atom as a whole, an atomic nucleus is a) very tiny but has most of the mass. b) quite large and has most of the mass. c) very tiny and has very little mass.
a
Compared to red light, blue light has a higher frequency and a) higher energy and shorter wavelength. b) higher energy and longer wavelength. c) lower energy and shorter wavelength.
a
Compared to the Sun, a star whose spectrum peaks in the infrared is a) cooler. b) hotter. c) larger.
a
How are wavelength, frequency, and energy related for photons of light? a. Longer wavelength means lower frequency and lower energy b. Longer wavelength means higher frequency and lower energy c. Longer wavelength means higher frequency and higher energy
a
How does angular resolution for a given diameter of a telescope depend on wavelength? a. it worsens as wavelength increases b. it improves as wavelength increases c. it may improve or worsen as wavelength increases, depending on other factors such as intensity and spectral range
a
How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope? a. the 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope b. the 8-meter telescope has 4 times the light-collecting area c. the 8-meter telescope has 8 times the light-collecting area
a
Ionization is the process by which a) electrons escape from atoms. b) liquid material enters the gas phase. c) molecules break apart into individual atoms.
a
Suppose a photon has a frequency of 300 million hertz (300 megahertz). What is its wavelength? a. 1 meter b. 1/300,000 c. 300 million meters
a
To achieve the same angular resolution as a visible-light telescope, a radio telescope would need to be a) much larger. b) slightly larger. c) in space.
a
What is a CCD? A) It is an electronic detector that can be used in place of photographic film for making images. B) It is an abbreviation for the world's largest operating telescope. C) It refers to any kind of instrument that can be hooked up to a telescope. D) It is a unit used by astronomers to measure angular resolution.
a
What is a CCD? A) It is an electronic detector that can be used in place of photographic film for making images. B) It is an abbreviation for the world's largest operating telescope. C) It refers to any kind of instrument that can be hooked up to a telescope. D) It is a unit used by astronomers to measure angular resolution.
a
What is the angular resolution of a telescope? a. its ability to distinguish two adjacent objects in the sky b. its ability to collect a large amount of light c. the amount of magnification d. its ability to separate light into various wavelengths
a
What is the purpose of adaptive optics? a. it reduces blurring caused by atmospheric turbulence for telescopes on the ground b. it allows several small telescopes to work together like a single larger telescope c. it allows ground-based telescopes to observe ultraviolet light that does not penetrate the atmosphere
a
What is the purpose of adaptive optics? a. it reduces blurring caused by atmospheric turbulence for telescopes on the ground b. it allows several small telescopes to work together like a single larger telescopes c. it is a special technology that allows the hubble space telscope to adapt to study many different types of atrsonomical objects
a
When an electron in an atom goes from a higher energy state to a lower energy state, the atom a. emits a photon of a specific frequency b. absorbs a photon of a specific frequency c. absorbs several photons of a specific freqency
a
Where should you put a telescope designed for ultraviolet observations? a) in Earth orbit. b) on an airplane. c) on a high mountaintop.
a
Which of the following is always true about images captured with X-ray telescopes? a. they are always shown in colors taht are not the true colors of the objects that were photographed b. they are always made with adaptive optics c. they always have very high angular resolution
a
Which of the following is true about low-mass stars compared to high-mass stars on the main sequence? A) Low-mass stars are cooler and less luminous than high-mass stars. B) Low-mass stars are hotter and more luminous than high-mass stars. C) Low-mass stars are cooler but more luminous than high-mass stars. D) Low-mass stars are hotter but less luminous than high-mass stars. E) Low-mass stars have the same temperature and luminosity as high-mass stars.
a
Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope? a. a refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light b. a refracting telescope produces refracted images while a reflecting telescope produces reflected images c. it is much easier to make a large refracting telescope than a large reflecting telescope
a
Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope? a. a refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light b. a refracting telescope produces refracting images while a reflecting telescope produces reflected images c. reflecting telescopes make much clearer images than can refracting telescopes of the same size
a
Which of the following statements best describes the two principal advantages of telescopes over eyes? a. telescopes can collect far more light with far better angular resolution b. telescopes have much more magnification and better angular resolution c. telescopes can collect far more light with far greater magnification
a
Which of the following terms is given to a pair of stars that appear to change positions in the sky, indicating that they are orbiting one another? A) visual binary B) eclipsing binary C) spectroscopic binary D) double star E) none of the above
a
Which of the following wavelength regions can be studied with telescopes on the ground? a. radio, visible, and very limited portions of the infrared and ultraviolet region b. all light with wavelengths longer than ultraviolet wavelengths c. all light with wavelengths shorter than infrared wavelengths d. infrared, visible, and ultraviolet light
a
Which of these stars in the most massive? a) a main-sequence A star b) a main sequence G star c) a main sequence M star
a
Which technology can allow a single ground-based telescope to achieve images as sharp as those from the Hubble Space Telescope? a) adaptive optics. b) grazing incidence mirrors. c) interferometry.
a
the wavelength of a wave is: a. the distance from one crest to the next b. the time from one crest passing to the next crest passing c. the number of crests that pass a point in a certain amount of time
a
which of the following is not one of the three main categories of observation generally used by astronomers? a. filtering to look at just a single color from an object b. timing to track how an object's brightness changes over time c. spectroscopy to spread an object's light into a spectrum d. imaging to get a picture of an astronomical object
a
From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nm. What can we conclude? a. the star is moving toward us b. the star is moving away from us c. the star is getting hotter
b
From lowest energy to highest energy, which of the following correctly orders the different categories of electromagnetic radiation? a. infrared, visible, UV, x-rays, gamma rays, radio b. radio, infrared, visible, UV, x-rays, gamam rays c. visible, infrared, x-rays, UV, infrared, radio
b
From the lowest energy to highest energy, which of the following correctly orders the different categories of electromagnetic radiation? a. infrared, visible light, UV, x-rays, gamma rays, radio b. radio, infrared, visible light, ultraviolet, X-rays, UV, gamma rays c. visible light, infrared, x-rays, ultraviolet, gamma rays radio
b
How much greater is the light-collecting are of a 6-meter telescope than that of a 3-meter telescope? a) two times b) four times c) six times
b
If Alpha Centauri were moved to a distance 10 times as far from Earths as it is now, its parallax angle would a) get larger b) get smaller c) stay the same
b
In a lab, the hydrogen Balmer alpha line has a wavelength of 656.30 nm. A star's spectrum reveals the same line to have a wavelength of 656.50 nm. a. the star must be cooler than the hydrogen in the lab b. the star is moving away from Earth c. the electrons in the H atoms in the tar have just dropped down two energy levels
b
Suppose you look at two stars that are separated in the sky by 0.1 arcsecond using a telescope with an angular resolution of 0.5 arcsecond. What will you see? a) two distinct stars b) one point of light that is the blurred image of both stars c) nothing at all.
b
Suppose you measure the parallax angle for a particular star to be 0.1 arcsecond. The distance to this star is A) 10 light-years. B) 10 parsecs. C) 0.1 light-year. D) 0.1 parsec. E) impossible to determine.
b
We can learn a lot about the properties of a star by studying its spectrum. All of the following statements are true except one. Which one? a. the peak of the star's thermal emission tells us its temperature b. the total amount of light in the spectrum tells us the star's radius c. we can identify chemical elements present in the star by recognizing patterns of spectral lines that correspond to particular chemicals
b
What do astronomers mean by light pollution? a. light pollution is a type of air pollution created by lightweight gases such as hydrogen and helium b. light pollution is light from human sources that makes it difficult to see the stars at night c. light pollution means contamination of light caused by chemical sin Earth's atmosphere
b
What do astronomers mean by light pollution? a. light pollution is a type of air pollution created by lightweight gases such as hydrogen and helium b. light pollution is light from human sources that makes it difficult to see the stars at night c. light pollution means contamination of light caused by chemicals in the Earth's atmosphere
b
Which of the following has the highest energy? a. blue light b. UV c. microwaves d. violet light
b
Which of the following is a form of electromagnetic radiation? a. electricity b. radio waves c. sound waves d. water waves
b
Which of the following is always true about images captured with X-ray telescopes? a. they are always made with adaptive optics b. they are always shown with colors that are not the true colors of the objects that were photographed c. they always have very high angular resolution
b
If two objects are the same size but one object is 3 times hotter than the other object, the other object emits a. 3 times more energy b. 9 times more energy c. 81 times more energy
c
The Hubble Space Telescope obtains higher-resolution images than most ground-based telescopes because it is a) larger. b) closer to the stars. c) above the Earth's atmosphere.
c
The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see? a. the two stars will appear to be touching, looking rather like a dumbbell b. the stars will not show up at all in your photograph c. the photo will seem to show only one star rather than two d. you will see two distinct stars in your photograph
c
The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see? a. two stars will appear to be touching, looking rather like a small dumbbell b. the stars will not show up at all in your photograph c. the photo will seem to show only one star rather than two
c
The spectral sequence in order of decreasing temperature is A) OFBAGKM. B) OBAGFKM. C) OBAFGKM. D) ABFGKMO. E) BAGFKMO.
c
The twinkling of stars is caused by a) variations in stellar brightness with time. b) light pollution. c) motion of air in our atmosphere.
c
The two ranges of electromagnetic radiation for which the Earth's atmosphere is reasonably transparent are a. uv and radio waves b. x-rays and visible radiation c. visible and radio radiation d. visible and far infrared radiation
c
Visible light occupies which position in the whole electromagnetic spectrum? a. between radio and infrared radiation b. between ultraviolet and x rays c. between infrared and UV d. between infrared and microwaves
c
What do we need to measure in order to determine a star's luminosity? a) apparent brightness and mass b) apparent brightness and temperature c) apparent brightness and distance
c
What is the purpose of interferometry? a. it is designed to prevent light pollution from interfering with astronomical observations b. it allows two or more small telescopes to achieve a larger light-collecting area than they would have independently c. it allows two or more small telescopes to achieve the angular reolsution of a much larger telescope
c
What type of spectrum would hot lava from a volcano emit? a. absorption line b. emission line c. continuous
c
When an atom loses an electron, it becomes a. sublimated b. dissociated c. ionized d. an isotope
c
When an atom loses an electron, it becomes.... a. sublimated b. dissociated c. ionized d. a plasma
c
Which of the following terms is given to a pair of stars that we can determine are orbiting each other only by measuring their periodic Doppler shifts? A) visual binary B) eclipsing binary C) spectroscopic binary D) double star E) none of the above
c
Which of these stars has the coolest surface temperature? a) an A star b) an F star c) an K star
c
Which of these stars has the largest radius? a) a supergiant A star b) a giant K star c) a supergiant M star
c
Which of these stars has the longest lifetime? a) a main-sequence A star b) a main sequence G star c) a main sequence M star
c
Why is a sunflower yellow? a) It emits yellow light. b) It absorbs yellow light. c) It reflects yellow light.
c
You observe the same spectral line in two stars that are identical in every way except that one rotates faster than the other. How does the spectral line differ between the two? a. there is no difference b. the line in the faster rotating star is blueshifted c. the line in the faster rotation star is broader
c
if two objects are the same size but one object is 3 times hotter than the other object, the hotter object emits (hint: energy is equal to óT^4) a. 3 times more energy b. 9 times more energy c. 81 times more energy
c
the frequency of a wave is: a. the distance from one crest to the next b. the time from one crest passing to the next cress passing c. the number of crests that pass a point in a certain amount of time d. the height of the crest from the node
c
when white light passes through a cool cloud of gas, we see a. visible light b. thermal radiation c. an absorption line spectrum d. an emission line spectrum
c
Star A has a surface temp of 3000K and star B has a surface temp of 9000K. Which of the following is true? a. Star A is brighter than Star B b. star A is "bluer" than star b c. star A is closer than Star B d. star A is 'redder' than star B
d
The primary reason for spreading many radio telescopes across a large area and combining signals at the central station is to: a. ensure that cloudy weather only affects a few of the telescopes b. avoid interference between signals from the separate telescopes b. collect more radiation than would be possible with the same telescopes clustered together d. produce a better angular resolution for radio sources
d
What is the primary advantage of the Hubble Space Telescope over ground-based telescopes? a. it is the largest telescope ever built b. its mirror is the most perfect ever built c. its instruments are more sophisticated than any on earth d. it is above the atmosphere
d
Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes? a. it never has to close because of cloudy skies b. it can observe infrared and ultraviolet light, as well as visible light c. stars do not twinkle when observed from space d. it is closer to the stars
d
Which of the following is the better angular resolution? a. 1.5 arcsec b. 15 arcsec c. 0.15 arcsec d. 0.015 arcsec
d
1) A star's luminosity is the A) apparent brightness of the star in our sky. B) surface temperature of the star. C) lifetime of the star. D) total amount of light that the star will radiate over its entire lifetime. E) total amount of light that the star radiates each second.
e
Which of the following luminosity classes refers to stars on the main sequence? A) I B) II C) III D) IV E) V
e
Which of the following statements about apparent and absolute magnitudes is true? A) The magnitude system that we use now is based on a system used by the ancient Greeks over 2,000 years ago that classified stars by how bright they appeared. B) A star with apparent magnitude 1 is brighter in the sky than one with apparent magnitude 2. C) The absolute magnitude of a star is another measure of its luminosity. D) A star's absolute magnitude is the apparent magnitude it would have if it were at a distance of 10 parsecs from Earth. E) All of the above are true.
e
What are the four major ways light and matter can interact?
emission, absorption, transmission, reflection/scattering
True or False: A radio telescope and an optical telescope of the same size have the same angular resolution
false
True or False: a radio telescope and an optical telescope of the same size have the same angualr resolution
false
True or False: the atomic mass number of an atom is equal to the number of protons in its nucleus
false
The star Vega has a higher surface temperature than the Sun. Then with IR indicating infrared and UV indicating ultraviolet, Vega emits _____ IR and _____UV flux than the Sun
more; more
TRUE/FALSE: If the distance between us and a star is doubled, the apparent brightness is decreased by a factor of four.
true
