A$tronomy Test #3

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

100 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

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.

What information about an astronomical object can be determined by observing its spectrum?

All of the above

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.

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 Cannon

Light which originates in hydrogen atoms in which electrons have jumped from high levels to the level n = 2 will be part of which series of spectral lines?

Balmer

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 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.

At an astronomical conference, an astronomer gives a report on a star that has recently begun to interest 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 persons used the ideas of quantum mechanics to describe why the spectral classification scheme is in order of decreasing temperature?

Cecilia Payne-Gaposchkin

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

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

Spectra from neutral atoms compared with spectra from ionized atoms of the same element

Have different sets of spectral lines

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

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.

The three laws dealing with the creation of various spectra are due to

Kirchhoff

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

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

M

How does the spectrum of a molecule differ from the spectrum of an atom?

Most atoms only have spectral lines at infrared wavelengths

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

Niels Bohr

Which star does look yellowish in color

Procyon

Which star is the coolest?

Proxima

Which star is the faintest?

Proxima

Which star is the most distant?

Proxima

Which star is the brightest?

Sirius

Which star is the hottest?

Sirius

Which star is the most luminous?

Sirius

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

Spectral class type

You observe a distant galaxy. You find that a spectral line normally found in the visible part of the spectrum is shifted toward the infrared. What do you conclude?

The galaxy is moving away from you

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?

The line in the faster rotating star is broader.

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.

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?

The star is moving away from us.

From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 485.9 nm. What can we conclude?

The star is moving toward us.

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?

The total amount of light in the spectrum tells us the star's radius.

Which star does look orangish in color?

Thuban

Which star is the closest?

Thuban

What are the standard units for luminosity?

Watts

An incandescent light (glowing tungsten filament) produces

a continuous spectrum, with the peak giving the temperature of the filament.

The Orion Nebula, M-42, is a hot, thin cloud of glowing gas, so its spectrum is

a few bright lines against a dark background

Which of the following statements about thermal radiation is always true?

a hot object emits more radio waves than a cool object.

Which of the following looks the brightest in the sky?

a star with magnitude -1

The Fraunhofer lines in the solar spectrum are actually

absorption lines due to the thin outer layer above the photosphere.

To have a negative ion, you must have:

added an electron to the outer electron shell

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

all of the above are true

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

an absorption line spectrum

An emission spectrum can be used to identify a(n)

atom

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

Which color star is likely to be the hottest

blue-violet

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

In space, positive ions are the result of

electrons being stripped off the outer electron shell for hot atoms

Which of the following statements about electrons is not true?

electrons orbit the nucleus rather like planets orbiting the Sun

Which of the following statements about photons is FALSE?

high energy photons have a high frequency

A star with a large parallax

is at a short distance from Earth.

An astronomer studying a particular object in space finds that the object emits light only in specific, narrow emission lines. The correct conclusion is that this object

is made up of a hot, rarefied gas

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

line shape

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

line shape

Why are molecular lines more complex than elemental spectral lines?

molecules can vibrate and rotate as well

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

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

no shift

The atomic number which designates the position of an element in the periodic table is equal to

number of protons in the nucleus of the atom

If light from a hot, dense star passes through a cool cloud of gas

only specific wavelengths of light will be removed from the spectrum

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

proper motion

Which star is the least luminous?

proxima

Thermal radiation is defined as

radiation that depends only on the emitting objects temperature.

Since the difference in energy between the different rotational states in a molecule is very small, many molecular lines can be observed with

radio or microwave telescopes

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 shows lines only in hot stars, this star must be relatively cool

Atoms in a thin, hot gas (such as a neon advertising sign) emit light

specific wavelengths, depending on the element.

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?

spectroscopic binary

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

The Physical force which holds an atom together is

the electromagnetic attraction between nucleus and electrons

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

Isotopes of a particular element in the periodic table have which nuclear property in common

the same number of protons but different numbers of neutrons

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

the size of a distant galaxy

What is the name given to 3/1 H

tritium

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

What are the standard units for apparent brightness?

watts per square meter

The splitting of spectral lines in the presence of strong magnetic fields is the

zeeman effect