Astronomy Light, Sun, Stars
The speed of light is equal to
3x10^8 m/s
T or F: Objects can either reflect or emit light.
False
Observing the Sun in H-alpha allows astronomers to observe solar features in the Chromosphere such as the dark features shown in this image which are called ____
Filaments
Who was the astronomer who is the "H" in H-R diagram?
Hertzsprung
The most common element in the Sun is
Hydrogen
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
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
With no spaces, list all the main-sequence spectral types from hottest to coolest. [spectral type order]
OBAFGKM
We see in the
Optical
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
Which statement about the Sun's rotation is TRUE?
The Sun rotates at different rates at different latitudes on the Sun
What happens when a high amount of energy is added to an atom?
The electrons become excited and increase their energy state
Astronomers have concluded that the Sun's activity varies in an 11-year cycle. Which of the following statements about this cycle is TRUE:
The number of sunspots gets larger and smaller over the course of 11 years
Which of the following statements about the Sun's photosphere is NOT TRUE?
The photosphere is significantly hotter than all the layers of the Sun beneath it (further inward) ^^^^^^^^^ The photosphere is much less dense than our Earth's atmosphere 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 The photosphere is the layer where the Sun becomes opaque (you can't see through it) Through a telescope, the photosphere looks mottled or granulated
True or False? There are many types of light
True
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 is NOT a product of the first step in the p-p chain of nuclear fusion?
a form of helium
According to the formula E=mc2
a little bit of mass can be converted into a substantial amount of energy
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 has the smallest mass?
a planet
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
continuous spectra
all colors
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
Which of the following statements about spectroscopic binary stars is FALSE?
an analysis of the ways the lines in the spectrum change allows us to calculate the star's distance directly
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
Binary stars orbit.
around a common center of mass
How fast do electro magnetic waves travel?
at the speed of light
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
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
warmer objects appear
bluer with a shorter wavelength
How objects emit light depends on...
both the object's temperature and density
emission spectra
bright light
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 dwarfs
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
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
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
The hottest zone in the Sun is the
core
Which part of the Sun has the greatest density?
core
Which part of the Sun's atmosphere has the lowest density (number of atoms per unit volume)?
corona
Which part of the Sun's atmosphere is the hottest?
corona
absorption spectra
dark lines
When blueshift occurs, the perceived wavelength of the wave would
decrease
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
What causes bright lines on an emission spectrum?
electrons falling to lower energy levels, releasing light
An emission spectra is created when
electrons in a cooling gas move down to a lower energy level
What causes an atom to absorb light?
electrons take in energy and jump to a higher energy level
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
The Doppler effect produces apparent changes in
frequency
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 has the highest frequency
gamma rays
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 Sun's hotter interior
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:
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
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
Which of the following characteristics of a single star (one that moves through space alone) is it difficult to measure directly?
its mass
what is reflected light
light bouncing off an object
What is emitted light?
light created and given off by an object
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
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)
Stars that lie in different places on the main sequence of the H-R diagram differ from each other mainly by having different:
masses
Astronomers observe a typical star using a telescope and a spectrometer. They will see: 1-an emission spectrum 2-more than one of these 3-an absorption spectrum 4-a continuous spectrum 5-a Doppler shift
more than one of these
Consider two identical stars. Star A is three times as far away as Star B. Star A therefore appears
nine times dimmer than Star B
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
Which is not and example of a true binary system? Select all that apply.
optical double.
Which of the following statements about photons is FALSE? 1- photon of visible light cannot pass through the atmosphere of the Earth, and thus cannot be seen at the Earth's surface 2- a gamma-ray photon carries more energy than a visible light photon 3- high energy photons have a high frequency (when thought of as waves) 4- photons always travel at the speed of light 5- photons each carry a specific amount of energy
photon of visible light cannot pass through the atmosphere of the Earth, and thus cannot be seen at the Earth's surface
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
Which of the following is NOT one of the fundamental particles that we find inside atoms?
positrons
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
Stars along the main sequence have similar...
radii
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)
In a star like the Sun, high temperatures are required to get H (hydrogen) nuclei to fuse because they ____ one another, due to their ____ electric charges.
repel, positive
The total energy a star emits is dependent on...
size, temperature
The Sun's chromosphere contains many jet-like projections that stick up into the transition region. These spikes of gas are called:
spicules
Why can astronomers not measure the diameters of stars directly?
stars are so far away, we cannot resolve (distinguish) their diameters
Which of the following is a way for astronomers to learn more about the interior of the Sun?
study the oscillations (pulsations) of the Sun's surface
In which order might you see these phenomena? (Type in either 1,2,3, or 4 in the space provided)
sunspots 1 prominences 2 solar flares 3 coronal mass ejections 4
A star's spectral type tells you its...
temperature but not luminosity
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 lines in its spectrum show a blue-shift
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
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
As you go upwards from the Sun's photosphere,
the density (number of atoms in a unit volume) decreases
Light intensity is dependent on the...
the inverse of the distance to the emitting object squared
Ninety percent of all stars (if plotted on an H-R diagram) would fall into a region astronomers call:
the main sequence
How do astronomers know how strong the magnetic field of the Sun is?
the measure the Zeeman effect (the splitting of spectral lines)
Most ultraviolet radiation does not penetrate to the Earth's surface. Instead it is absorbed in:
the ozone layer
Which of the following statements about electromagnetic radiation is false? it is given off by all objects that are not at a temperature of absolute zero the radiation consists of tiny charged particles given off by the nuclei of atoms different waves of electromagnetic radiation differ in their wavelength or frequency it always spreads out at the speed of light
the radiation consists of tiny charged particles given off by the nuclei of atoms
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
Why are line emission spectra of elements called "atomic fingerprints"?
they are all unique
Sunspots are darker than the regions of the Sun around them because
they are cooler than the material around them (although still very hot compared to Earth temperatures)
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
Two stars are giving off electromagnetic radiation. The hotter star will:
will give off a continuous spectrum of waves, will have a higher average frequency of radiation, will radiate energy at more than one wavelength, give off more radiation at all wavelengths
In the future, several students living onboard a space station decide to have a race among different types of electromagnetic radiation. Which of the following travels through space the fastest? 1-you can't fool me, all of these travel through space at the same speed 2-visible light 3-infrared 4-x-rays 5- radio waves
you can't fool me, all of these travel through space at the same speed
