Astronomy 1, Test 3

The most distant stars we can measure stellar parallax for are approximately:

10,000 parsecs away

In a visual binary system with circular orbits, if in 20 years the two stars' position angles have shifted by 30 degrees, the pair's period must be:

240 years

An atom of the element iron has an atomic number of 26 and an atomic mass number of 56. If it is neutral, how many protons, neutrons, and electrons does it have?

26 protons, 30 neutrons, 26 electrons

An incandescent light (glowing tungsten filament) produces:

A continuous spectrum, with the peak giving the temperature of the filament

How much electrical charge does an atom with 6 protons, 6 neutrons, and 5 electrons have?

A positive charge of +1

Astronomers have discovered stars even cooler than the traditional spectral type M stars recently. Astronomers have given 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

Which of the following looks the brightest in the sky?

A star with a magnitude of -1

Which of the following can astronomers NOT learn from studying the spectrum of a star?

All of the above can be learned from studying the spectrum

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?

All stars that rotate show a huge Doppler shift toward the blue end of the spectrum

Which star does look orangish in color?

Alpha Centauri

Which star does look yellowish in color?

Alpha Centauri

Which star is the most luminous?

Alpha Centauri

When white light passes through a cool cloud of gas, we see:

An absorption line spectrum

When an atom absorbs a photon containing energy, any of the following can happen except which?

An electron moves from an upper energy level to a lower one

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

The astronomer who, at the turn of the century, measured the spectra of hundreds of thousands of stars, leaving a catalog that astronomers used for the rest of the century, was:

Annie Canon

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 their stars

Are made of significantly different elements

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?

Because of proper motion, a number of the familiar constellations will look somewhat different in a million years

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

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

Which color star is likely to be the hottest?

Blue-violet

Which of the following persons used the ideas of quantum mechanics to describe why the spectral classification scheme is in order of decreasing temperature?

Cecilia Payne-Gaposchkin

By which appropriate method the chemical composition of a star can be deduced from its spectrum?

Characteristic lines

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

In comparing first magnitude Deneb with second magnitude Polaris, we find that:

Deneb appears 2.5 times brighter to us than does Polaris

By which appropriate method the radial velocity of a star can be deduced from its spectrum?

Doppler shift

In a spectroscopic binary, if a pair shows a combined set of lines tonight, but a maximum split two nights later, its orbital period must be:

Eight Days

Which of the following statements about electrons is not true?

Electrons orbit the nucleus rather like planets orbiting the Sun

When an electron in an atom goes from a higher energy state to a lower energy state, the atom:

Emits a photon of a specific frequency

Which of the following statements about photons is FALSE?

High energy photons have a high frequency

Perhaps the greatest of the Greek astronomers, ________ compiled the first catalog of stars, accurately measured their positions, and defined the basic system of stellar brightnesses.

Hipparchus

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

If hydrogen is the most common element in the universe, why do we not see the lines of hydrogen in the spectra of the hottest stars?

In the hottest stars, hydrogen atoms are ionized, and so there are no electrons to produce lines in the spectrum

By which appropriate method the gas density, axial rotation, and magnetic field of a star can be deduced from its spectrum?

Line Shape

How do astronomers learn what elements are present in a given star?

Look at the absorption lines in its spectrum

After days and days of work, a group of graduate students has finally measured the wavelengths of hundreds 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

The idea that atoms radiate energy only when their electrons move from higher to lower energy levels was first advanced by:

Niels Bohr

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 brighter

The light from an object moving tangentially (to your left or right) will exhibit:

No shift

Which of the following types of star is the coolest (has the lowest surface temperature)?

O

Which star is the most distant?

Procyon

The motion of a star across the sky (perpendicular to our line of sight) is called its

Proper Motion

Which star is the closest?

Proxima

Which star is the coolest?

Proxima

Which star is the least luminous?

Proxima

Suppose you built a scale-model atom in which the nucleus was the size of a tennis ball. About how far would the cloud of electrons extend?

Several kilometers

A graduate student has spent a whole year doing 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 is the kind of element that quickly bonds with others, all the helium in this star must be in the form of molecules

What star is the hottest?

Sirius

Which star is the brightest?

Sirius

By which appropriate method the temperature of a star can be deduced from its spectrum?

Spectral class type

Star A and star B have the same temperature, but star B is more luminous than star A. What can you infer about these two stars?

Star B must be bigger

The absolute magnitude of a star is its brightness as seen from a distance of:

Ten Parsecs

In general, the narrower the spectral line of a star:

The bigger the star is

If one object has a large redshift and another object has a small redshift, what can we conclude about these two objects?

The one with the large redshift is moving away from us faster than the one with the small redshift

If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?

The planet is rotating

The depth of the dip in a star's brightness due to the transit of a planet depends most directly on:

The planet's size

Which of the following could not be determined by an observation that uses only spectroscopy?

The size of a distant galaxy

Which of the following statements about spectral types of stars is true?

The spectral type of a star can be used to determine its surface temperature

Which star is the faintest?

Thuban

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?

Visual Binary

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?

Visual Binary