ASTR121 Exam 1
Imagine that a brilliant but quirky scientist in the biology department manages to put you in a deep freeze and you wake up in a million years. Which of the following statements about the sky you would see in that future time is correct? a)because of proper motion, a number of the familiar constellations will look somewhat different in a million years b)all the stars and constellations would look exactly the same as they do now c)all the stars we can see in the sky today will have died in a million years d)at the present time, astronomers do not know enough about the universe to say what the sky might be like in a million years e)if you could see them up close, almost all the stars in the sky today will have changed their color significantly in a million years
a
Two stars have the same diameter and are at the same distance from us (but in different parts of the sky.) Star A has a temperature of 4000 K, while star B has a temperature of 8000K. Which of the following statements is true: a) star B has 16 times the energy flux (luminosity) that star A has b) the two stars have the same total energy flux (luminosity) c) Sorry, professor, we don't have enough information to compare the energy flux (luminosity) of the two stars d) star B has twice the energy flux (luminosity) that star A has e) star B has one half the energy flux (luminosity) that star A has
a
Which of the following can astronomers NOT learn from studying the spectrum of a star? a)you can't fool me, all of the above can be learned from studying the spectrum b)its surface temperature c)whether it is rotating slow or fast d)whether it is a star the size of the Sun or a giant star e)its motion toward or away from us
a
Which of the following characteristics of a single star (one that moves through space alone) is it difficult to measure directly? a)its mass b)its chemical composition c)its apparent brightness d)its temperature e)you can't fool me, all of these are quite easy to measure directly
a
Which of the following statements about electromagnetic radiation is FALSE? a) the radiation consists of tiny charged particles given off by the nuclei of atoms b) it is given off by all objects that are not at a temperature of absolute zero c) it always spreads out at the speed of light d) different waves of electromagnetic radiation differ in their wavelength or frequency
a
Which of the following statements about interstellar matter is FALSE? a)if the matter were spread out evenly, it would be about as dense as the Earth's atmosphere b)it is clumpy: much of it is distributed in patchy, irregular clouds c)the total mass in interstellar matter in our Galaxy is about 5% of the mass in stars d)it also includes grains of dust e)99% of it is in the form of gas
a
Which of these stars will take the SHORTEST time to go from the earliest protostar stage to the main sequence? a)a star ten times the mass of our Sun b)all of these stars take the same time to get to the main sequence c)a star ½ the mass of our Sun d)a star equal to the mass of our Sun e)a star 1/10th the mass of our Sun
a
Which of the following is NOT a product of the first step in the p-p chain of nuclear fusion?
a form of helium
When astronomers discuss a nebula, what are they talking about?
a giant cloud of gas and dust between or among the stars
At the end of the p-p chain of nuclear fusion in the Sun, hydrogen nuclei have been converted into:
a helium nucleus
The Orion Nebula is
a large cloud of gas and dust illuminated by the light of newly formed stars within it
According to the formula E=mc2
a little bit of mass can be converted into a substantial amount of energy
Who pays the bill for the energy generated by nuclear fusion in the Sun? In other words, where does the energy pouring out of the Sun come from ultimately?
a little bit of mass is lost in each fusion reaction and is turned into energy (the Sun is losing mass)
Which of the following, produced at the core of the Sun, will take the shortest time to emerge from the Sun's photosphere (surface)?
a neutrino
We discussed that light sometimes acts like a photon. What is a photon?
a self-contained "packet" of electro-magnetic energy
In recent decades, astronomers discovered stars even cooler than the traditional spectral type M stars recently. Astronomers gave these cool stars a new spectral type, L. If you wanted to go out and find more such type L stars, what kind of instrument would it be smart to use?
a sensitive infra-red telescope
An astronomer wants to observe a cloud of dust in a relatively close part of the Galaxy. Unfortunately, this dust cloud is not located in the direction of a crowded region of stars. What instrument would be the most help in finding this cloud.
a sensitive infra-red telescope in orbit around the earth
A star moving toward the Sun will show:
a shift in the spectral lines toward the blue end (as compared to the laboratory positions of these lines)
A star that is quite hot and has a very small radius compared to most stars is called
a white dwarf
An HII region is
a zone around a hot star where hydrogen atoms are ionized
An artist who likes working with sources of light decides to make a modern sculpture out of electrified glass tubes that contain very thin (rarified) neon gas. When the sculpture is finished, and the electricity is turned on, the tubes glow with a rich red color. What we are seeing is:
an emission spectrum
If an astronomer wants to find and identify as many stars as possible in a star cluster that has recently formed near the surface of a giant molecular cloud (such as the Trapezium cluster in the Orion Nebula), what instrument would be best for her to use?
an infra-red telescope (and camera)
A team of astronomers takes spectra of thousands of different stars in different parts of the sky. The spectra show significant differences. The main reason the spectra of the stars do not all look alike is that the stars
are made of significantly different elements
Solar wind particles can be captured by the Earth's magnetosphere. When these particles spiral down along the magnetic field into the atmosphere, they are responsible for:
aurorae
Astronomers have concluded that the Sun's activity varies in an 11-year cycle. Which of the following statements about this cycle is TRUE: a)The Sun's activity cycle shows absolutely no connection to its magnetic field b)The number of sunspots gets larger and smaller over the course of 11 years c)When sunspots are at a minimum, we get the largest number of flares and prominences d)The Sun's activity cycle is directly connected to the number of earthquakes at the continental plate boundaries on Earth e)Every 11 years sunspots completely cover the Sun, making its surface much darker
b
Which of the following statements about the Sun's photosphere is NOT TRUE? a)The photosphere is the layer where the Sun becomes opaque (you can't see through it) b)The photosphere is significantly hotter than all the layers of the Sun beneath it (further inward) c)The photosphere is not a solid layer; if a spaceship (that could withstand the heat) fell through it, it wouldn't feel anything when reaching the photosphere d)Through a telescope, the photosphere looks mottled or granulated e)The photosphere is much less dense than our Earth's atmosphere
b
Some "superstars" give off more than 50,000 times the energy of the Sun. Why are there no such stars among the stars that are close to the Sun?
because such very luminous stars are extremely rare, and thus any small neighborhood in the Galaxy is unlikely to contain one of them
Why are astronomers much more interested in the luminosity of a star than its apparent brightness?
because the luminosity tells us how bright a star really is, while apparent brightness only tells us how bright it happens to look from Earth
At an astronomical conference, an astronomer gives a report on a star that interests astronomers because of hints that it may have a planet around it. In his report the astronomer gives the average speed with which this star is moving away from the Sun. How did the astronomer measure this speed?
by looking at the Doppler shift in the lines of the star's spectrum
Which of the following is a method for measuring the diameter of a star? a)measuring the spectrum of a spectroscopic binary b)watching the body of the Moon go across the star c)more than one of the above d)comparing the color of a star seen high above our heads and then again when it's near the horizon e)getting the light curve of an eclipsing binary star
c
Why is it so difficult for astronomers to see new stars in the process of birth? a)birth happens very quickly, so it is hard to "catch" stars "in the act" b)the size of a newly forming star is typically quite small and thus hard to make out c)all of the above d)most stars are born inside dusty clouds, which block any light that may be coming from the stars e)protostars which are not yet doing fusion do not give off a lot of visible light
c
Stars that lie in different places on the main sequence of the H-R diagram differ from each other mainly by having different:
masses
An exhausted-looking astronomer comes off the mountain where her observatory is located and tells you she has been doing photometry all night. What has she been up to?
measuring the brightness of different stars
Two stars are giving off electromagnetic radiation. The hotter star will: a) will have a higher average frequency of radiation b) will radiate energy at more than one wavelength c) will give off a continuous spectrum of waves d) give off more radiation at all wavelengths e) all of the above
e
Using a good pair of binoculars, you observe a section of the sky where there are stars of many different apparent brightnesses. You find one star that appears especially dim. This star looks dim because it is: a)very low luminosity b)very far away c)radiating most of its energy in the infrared region of the spectrum d)partly obscured by a cloud e)it could be more than one of the above; there is no way to tell which answer is right by just looking at the star
e
Which of the following statements about photons is FALSE? a) high energy photons have a high frequency (when thought of as waves) b) a gamma-ray photon carries more energy than a visible light photon c) photons each carry a specific amount of energy d) photons always travel at the speed of light e) photon of visible light cannot pass through the atmosphere of the Earth, and thus cannot be seen at the Earth's surface
e
Which of the following statements about spectroscopic binary stars is FALSE? a)we can often use the changes in the positions of the spectral lines to measure the radial velocity of the stars in the system b)some of the lines in the spectrum are double, with the spacing changing over time c)we can use the spectrum to determine the sum of the masses of the two stars d)visually we can only see one star e)an analysis of the ways the lines in the spectrum change allows us to calculate the star's distance directly
e
Which of the following statements about the violent events on the Sun called flares is FALSE? a)astronomers think that flares are connected with sudden changes in the magnetic field of the Sun b)the visible light we see from a flare is only a tiny fraction of the energy it releases c)a flare can release energy equivalent to a million hydrogen bombs d)flares happen more often during solar maximum, and sometimes during those periods, there can be several in one day e)flares originate in the upper part of the corona, in the regions called coronal holes
e
Which statement about the Sun's rotation is TRUE? a)The Sun rotates only at the equator, where the sunspots are found; the rest of the Sun does not rotate b)The Sun does not rotate; only planets rotate c)Only the atmosphere of the Sun rotates, not the main body of the Sun d)The Sun rotates once a day e)The Sun rotates at different rates at different latitudes on the Sun
e
Astronomers identify the main sequence on the H-R diagram with what activity in the course of a star's life?
fusing hydrogen into helium in their cores
What happens as an electron falls from a higher level to a lower level in an atom?
a photon is given off
Which of the following are the small regions that are the embryos of stars (where individual stars are most likely to be born)?
the cores within the clumps of molecular clouds
Who was the astronomer who is the "hH" in H-R diagram?
Hertzsprung
Which law do astronomers use to determine the masses of the stars in a spectroscopic binary system?
Kepler's 3rd Law
After a lot of work, a group of graduate students has finally measured the wavelengths of many dozens of lines in the spectrum of a distant star. If a number of the lines come from molecules such as titanium oxide, the star is likely to be which spectral type:
M
Which of the following types of star is the coolest (has the lowest surface temperature)?
M
What is the best reason astronomers have come up with to explain why sunspots are cooler and look darker?
Sunspots are places where the strong magnetic fields in the Sun resist the upward motion of bubbling hot gases from underneath
What mechanisms do astronomers believe is responsible for making the Sun's outer atmosphere so much hotter than its photosphere?
The Sun's magnetic field interacting with the charged particles that make up the atmosphere
a hertz is
Unit of frequency
An idealized object that does not reflect or scatter any radiation that hits it, but simply absorbs every bit of radiation that falls on it is called:
a blackbody
Which of the following has the smallest mass? a)you can't fool me, all the above have roughly the same mass b)the sun c)a brown dwarf d)the smallest mass star that can still have fusion of hydrogen to helium in its core e)a planet
a planet
Astronomers call a ball of matter that is contracting to become a star
a protostar
An astronomer wants to observe a cloud of cold neutral (not ionized) hydrogen, far away from any stars. What would be an instrument that could help in this task?
a radio telescope, tuned to a wavelength of about 21 centimeters
An astronomer observes two ordinary stars. The first one turns out to be twice as hot as the second. This means that the first one radiates:
about 16 times the energy of the second
To go from a lower level in an atom to a higher level, an electron must
absorb a photon of energy
In the future, several students living on board a space station decide to have a race among different types of electromagnetic radiation. Which of the following travels through space the fastest?
all of these travel through space at the same speed
In an H-R diagram, where can you see the spectral type of a star (whether it is an O type star or a G type star, for example)?
along the bottom (the horizontal axis)
One of your good friends asks you to point out the stars with the smallest mass on an H-R diagram that you are studying. Where are you sure to find the stars with the lowest mass on any H-R diagram?
among the stars at the bottom right of the main sequence
Supposing we launched a very fast dart from the Space Shuttle, pointed in some direction away from any planet, so that it could travel beyond the solar system. What would it be most likely to hit first after traveling outward for a while?
an atom of interstellar gas
How fast do electro-magnetic waves travel?
at the speed of light
Which of the following has the longest wavelength? a) visible b) radio waves c) x ray d) ultraviolet
b
Why do different types of atoms (elements) give off or absorb different spectral lines?
because the spacing of the energy levels is different in different atoms
Two stars that are physically associated (move together through space) are called
binary stars
Which color star is likely to be the hottest?
blue-violet
Some objects in space just don't have what it takes to be a star. Which of the following is a "failed star", an object with too little mass to qualify as a star?
brown dwarf
One key difference that astronomers use to distinguish between brown dwarfs and high-mass planets is that:
brown dwarfs are able to do deuterium fusion in their cores, while planets can't
Which of the following is NOT a way astronomers discover clouds of interstellar matter that have a large amount of dust in them?
by giving off x-rays from hot gas surrounding the dust cloud
the hotter region directly above the sun's visible surface is called the
chromosphere
Astronomers now understand that the dark regions or rifts visible in parts of our Galaxy that are otherwise crowded with stars are caused by:
clouds with a considerable amount of dust which blocks the light of the stars behind them
When great currents of hot material rise inside the Sun (and cooler material sinks downward), energy is being transferred by a process known as:
convection
Where in the sun does nuclear fusion occur?
core
the hottest zone in the sun is the
core
Which part of the Sun's atmosphere is the hottest?
corona
which part of the sun's atmosphere has the lowest density?
corona
Which of the following has the highest frequency? a) radio waves b) ultraviolet c) visible light d) gamma rays
d
Astronomers arrange the stars into groups called spectral classes (or types) according to the kinds of lines they find in their spectra. These spectral classes are arranged in order of:
decreasing surface temperature
Astronomers observe a typical star using a telescope and a spectrometer. They will see: a) a continuous spectrum b) an absorption spectrum c) a doppler shift d) an emission spectrum e) more than one of the above
e
The fact that each type of atom has a unique pattern of electron orbits helps explain why
each type of atom shows different absorption or emission spectra
For what type of star can astronomers measure the diameter with relative ease?
eclipsing binary stars
Recently, some engineers and scientists have proposed building spaceships with enormous "sails" that catch the solar wind and use it to move the ship. What kinds of particles would be hitting this sail (i.e., what is the solar wind mostly made of):
electrons and protons
In the Sun, when a positron and an electron collide, they will produce:
energy in the form of a gamma ray
If the "fuel" for nuclear fusion is nuclei of hydrogen, and the Earth's oceans are filled with hydrogen atoms in water all being jostled together, why isn't there a lot of fusion happening in our oceans?
for hydrogen nuclei to fuse, they must get very close to each other, which the nuclei in the oceans cannot do
Astronomers use the term interstellar matter to refer to:
gas and dust that lies between stars
In order for a cold atom of hydrogen to emit a 21-cm wave, it must first be in a slightly higher energy state. What event usually "kicks" the hydrogen atom up to this higher state?
gas atoms within the cloud collide
Which of the following is not part of some active regions on the Sun?
granulation
the energy of random atomic and molecular motion is called
heat
The granulation pattern that astronomers have observed on the surface of the Sun tells us that:
hot material must be rising from the suns hotter interior
When an astronomer rambles on and on about the luminosity of a star she is studying, she is talking about:
how much energy the star gives off each second
Studies of the spectra of stars have revealed that the element that makes up the majority of the stars (75% by mass) is
hydrogen
You are an astronomer whose supervisor has just forbidden drinking alcoholic beverages near the observatory. In frustration, you undertake a search for alcohol molecules in space. Where would your search be most likely to succeed?
in an interstellar cloud of gas and dust
If you want to find stars that are just being born, where are the best places to search?
in giant molecular clouds
Imagine that powerful telescopes in the future give us a truly representative sampling of all the stars in the Sun's cosmic neighborhood. Where on the H-R diagram would most of the stars in our immediate vicinity lie?
in the lower right, among the least luminous main sequence stars
you are alone in a large, completely dark auditorium on Earth. What kind of telescope should I use from the other side of the auditorium to detect the electromagnetic radiation emitted by your body?
infra-red
As astronomers have learned more about the structure of the Sun, they have found that it
is made entirely of hot gas
Measurements show a certain star has a very high luminosity (100,000 x the Sun's) while its temperature is quite cool (3500o K). How can this be?
it must be quite large in size
What happens to the positron created during the p-p chain of nuclear reactions inside the Sun?
it quickly collides with an electron and turns into gamma ray energy
When a star settles down to a stable existence as a main-sequence star, what characteristics determines where on the main sequence in an H-R diagram the star will fall?
its mass
Astronomers believe that disks of material will form around protostars that are spinning. Which of the following observed phenomena is a good indication of the presence of a disk around a protostar?
jets and Herbig-Haro objects
We have two waves of light, A and B. Wave A has a higher frequency than wave B. Then wave B must have:
longer wavelength
How do astronomers learn what elements are present in a given star?
look at the absorption lines in its spectrum
Given the presence of dust throughout the disk of the Milky Way Galaxy, what is the best technique for learning about more distant regions of our galaxy's disk.
look for radiation at long wavelengths, for example in the infrared region of the spectrum
Astronomers now realize that active regions on the Sun are connected with
loops of magnetic field emerging from the surface of the Sun
The most common kinds of stars in the Galaxy have
low luminosity compared to the Sun
Stars on the main sequence obey a mass-luminosity relation. According to this relation,
luminosity is proportional to mass to the fourth power (luminosity increases strongly with mass)
In figuring out the evolutionary tracks on the H-R diagram, astronomers
make model stars on a computer and then follow how their characteristics will change with time
An astronomer discovers a new star and wants to measure its temperature. She would typically do this by:
making a blackbody curve and finding the wavelength of the peak (maximum)
Which of the following particles has the lowest mass?
neutrino
Two stars have the same luminosity, but star B is three times farther away from us than star A. Compared to star A, star B will look
nine times fainter
Today we realize that the source of energy for the Sun is a process called
nuclear fusion
The Sun is an enormous ball of gas. Left to itself, a ball of so many atoms should collapse under its own tremendous gravity. Why is our Sun not collapsing?
nuclear fusion in the core keeps the temperature and the pressure inside the Sun at a high enough level so that gravity is balanced
Where on the H-R Diagram would we find stars that look red when seen through a telescope?
only on the right side of the diagram and never on the left
You are out on the beach, enjoying the warm sunshine with friends. As you glance up at the Sun (only briefly we hope), the part of the Sun that you can see directly is called its:
photosphere
When we use the light of atoms such as hydrogen and calcium to examine the Sun's outer layers, we can see bright "clouds" in the chromosphere right around the location of sunspots. These bright clouds are given the name:
plages
The material inside the Sun is in the form of a
plasma
If an astronomer wanted to find some relatively complex molecules in space, what technique should she use?
point a radio telescope into regions in the galaxy where there is a lot of dust
The antimatter version of an electron is called a
positron
Astronomers call the motion of a star across the sky (perpendicular to our line of sight) its
proper motion
When energy is first produced by fusion deep in the core of the star, that energy moves outward mostly by what process?
radiation
A graduate student has done a careful analysis of the spectrum of a star. While she has found lines from many elements, there was not a trace of the element helium in the spectra she has been analyzing. From this she can now conclude:
since helium shows lines only in hot stars, this star must be relatively cool
A white dwarf, compared to a main sequence star with the same mass, would always be:
smaller in diameter
When two light elements collide to undergo nuclear fusion
some of the energy in their mass is released
The fastest speed in the universe is:
speed of light
The Sun's chromosphere contains many jet-like projections that stick up into the transition region. These spikes of gas are called:
spicules
Two stars have the exact same luminosity, but star Y is four times dimmer looking that star X. This means that
star Y is twice as far away as star X
Which of the following looks the brightest in the sky?
star with a magnitude of -1
Why can astronomers not measure the diameters of stars directly?
stars are so far away, we cannot resolve (distinguish) their diameters
An astronomer whose secret hobby is riding merry-go-rounds has dedicated his career to finding the stars that rotate the most rapidly. But the stars are all very far away, so none of them can be seen to spin even when he looks through the largest telescopes. How then can he identify the stars that rotate rapidly?
stars that rotate have much wider lines in their spectra than stars that do not
Which of the following is a way for astronomers to learn more about the interior of the Sun?
study of oscillation (pulsations) of the Sun's surface
How do fragile structures like acetaldehyde (CH3CHO) molecules survive in the harsh environment of interstellar space? Why are they not destroyed by high-energy radiation from stars?
such molecules are found only in dense clouds that have a lot of dust; the dust keeps the radiation from hot stars from reaching the molecules
An H-R Diagram plots the luminosity of stars against their
surface temperature
Sunspots are darker than the regions of the Sun around them because
the are cooler than the material around them (although still very hot compared to Earth temps)
A friend of yours who has not taken an astronomy class looks at your textbook and really likes the picture of the Pleiades, a cluster of stars surrounded by a bluish reflection nebula. She wants to know what causes that beautiful blue glow. To explain it to her, you want to compare the process that causes the blue glow to something that is in your friend's everyday experience. Which of the following terrestrial phenomena is the result of the same type of process that makes a reflection nebula in space?
the blue color of the Earth's sky
as you go upwards from the sun's photosphere
the density (number of atoms in a unit volume) decreases
When an astronomer measures a color index for a star, what is she measuring? (be careful here, this question is tricky)
the difference between how bright a star looks at two different wavelength regions
Ninety percent of all stars (if plotted on an H-R diagram) would fall into a region astronomers call:
the main sequence
Most ultraviolet radiation does not penetrate to the Earth's surface. Instead it is absorbed in:
the ozone layer
the suns photosphere is
the part of the sun from which the light comes that we see when we look at the sun with our eyes
Which of the following is NOT one of the fundamental particles that we find inside atoms?
the positrons
Astronomers use the term interstellar extinction to refer to:
the scattering and absorption of starlight by dust grains in space
In the formula E=mc2, the letter c stands for
the speed of light
A college friend of yours who has been postponing taking any science courses hears you talking about the generation of nuclear energy in the Sun and makes the following observation: "The whole idea of the atomic nucleus is pretty ridiculous. If an oxygen nucleus consists of eight protons and eight neutrons, the charge on that nucleus is positive. Since even I learned in high school that like charges repel, such a nucleus would find all its positive protons repelling and quickly fall apart." How would you answer his argument?
the strong nuclear force, which is attractive over short distances like the nucleus, and stronger than electricity, holds the nucleus together
(In the absence of a strong magnetic field), what is the chief factor that determines what type of electromagnetic radiation objects give off:
their temperature
If it takes an average of 14 billion years before any proton inside the Sun will undergo fusion, and the Sun is only about 5 billion years old, why do astronomers believe that fusion is going on there now?
there are an enormous number of protons inside the Sun, and some of them will fuse much sooner than the average
Most of the really bright stars in our sky are NOT among the stars that are very close to us. Why then do they look so bright to us?
these stars are intrinsically so luminous, that they can easily be seen even across great distances
How do astronomers know how strong the magnetic field of the Sun is?
they measure the zeeman effect (the splitting of spectral lines)
The dust in the dust clouds in interstellar space consists of
tiny solid grains
A star whose temperature is increasing but whose luminosity is roughly constant moves in what direction on the H-R diagram?
to the left
The process of fusion that keeps our sun shining begins with which building blocks?
two protons
The light which allows you to see this very interesting exam is made up of waves. In these waves, the distance between crests is called the:
wavelength
An astronomer is observing a star which puzzles her. The lines in the star's spectrum indicates that the star is very hot and should therefore be blue. But the star looks reddish in photographs and in measurements of the continuous spectrum. What is one possible explanation of this puzzle?
we are seeing the light of the star through layers of interstellar dust
Astronomers studying regions like the Orion Giant Molecular Cloud have observed that a wave of star formation can move through them over many millions of years. What sustains such a wave of star formation in a giant molecular cloud?
when massive stars form, their ultraviolet radiation and later their final explosions compress the gas in the cloud and cause a new group of stars to form
Astronomers identify the "birth" of a real star (as opposed to the activities of a protostar) with what activity in the star?
when nuclear fusion reactions begin inside its core
We observe a glowing cloud of gas in space with a spectroscope. We note that many of the familiar lines of hydrogen that we know on Earth seem to be in a different place. They are shifted toward the blue or violet end of the spectrum compared to their positions in the spectrum of glowing hydrogen gas on Earth. From this we can conclude that:
the cloud is moving toward us
You are an astronomy graduate student and you are observing the big Orion Nebula from an airplane that has a good-sized infrared telescope built into it (there really is such a plane.) On an infrared image of the Nebula, what would particularly stand out?
the clouds of the nebula that have a lot of dust in them
Which part of the Sun has the greatest density?
the core
A Herbig-Haro (HH) object is
where a jet from a star in the process of being born collides with (and lights up) a nearby cloud of interstellar matter
I want to examine the surface of a planet that is covered by a thick atmosphere (which includes oxygen and contains a very thick layer of water clouds that never clears). What wavelength of electromagnetic radiation would I be smartest to use:
radar waves
Not all wavelengths of electromagnetic radiation can penetrate the Earth's atmosphere. Of the following types of waves that come from space, which one are you likely to be able to detect most easily from our planet's surface:
radio waves of the wavelength that carry FM broadcasts
A fashion designer decides to bring out a new line of clothing which reflects the longest wavelength of visible light. What color will these articles of clothing be to the human eye?
red
When a star or galaxy is moving away from us, we observe the Doppler effect by seeing the lines in its spectrum
red-shifted (shifted toward the red end of the light spectrum)
Astronomers were at first surprised to find complicated molecules in the interstellar medium. They thought ultra-violet light from stars would break apart such molecules. What protects the molecules we observe from being broken apart?
such molecules form in clouds that contain significant amounts of dust, and the dust in the cloud protects them from ultra-violet rays
The Stefan-Boltzmann Law relates the energy flux coming from a blackbody (such as a star) to its:
temperature
Wien's Law relates the wavelength at which a star gives off the greatest amount of energy to the star's
temperature
I am measuring the spectrum of the stars in a spectroscopic binary system. When one of the stars is moving toward the Earth in its orbit, we observe
that the line in its spectrum show a blue-shift
Why is an absorption spectrum especially useful for astronomers?
It has dark lines in it that allow astronomers to determine what elements are in the star
The first astronomer who did photometry in a systematic way (even though he did not have a telescope) was
Hipparchus
The red color we see on a lot of photographs of nebulae comes from which element?
Hydrogen
most common element in the sun is
Hydrogen
Stars that do not have what it takes to succeed as a star (i.e. do not have enough mass to fuse hydrogen into helium at their centers) are called:
Brown Dwarf
