Astronomy Final

Parallax would be easier to measure if

Earth's orbit was larger.

We can determine the surface temperature of a star

Either "a" or 'b" will work but "b" is more precise

Which of the following cannot be determined from the spectrum of a star?

tangential (perpendicular to line of sight) velocity

A star's absolute magnitude depends only on the star's

temperature and diameter.

The photosphere is very thin because

the H- ion is a very good absorber of photons and causes the gas of the photosphere to be opaque.

Sunspots are known to be magnetic phenomena because

the Zeeman Effect is observed in sunspots.

A planetary nebula is

the expelled outer envelope of a medium mass star.

Absorption lines produced by the interstellar medium indicate that some components of the interstellar medium are cold and of a very low density because

the lines are extremely narrow.

The mass of a single galaxy might be found by

the rotation curve method.

Modern astronomers suspect the corona is heated by

the solar magnetic field.

Sunspots are dark because

the strong magnetic field inhibits the currents of hot gas rising from below.

Absolute zero is

the temperature at which atoms have no remaining energy from which we can extract heat.

The assumption of isotropy states that

the universe looks the same in all directions.

The main sequence has a limit at the lower end because

there is a minimum temperature for hydrogen fusion.

The fact that many radio lobes emit more intensely from the side away from the galaxy suggests that

they are created by jets from the galaxy.

We know that giant stars are larger in diameter than the sun because

they are more luminous but have about the same temperature.

The lowest-mass stars cannot become giants because

they cannot heat their centers hot enough.

A neutron star is expected to spin rapidly because

they conserved angular momentum when they collapsed.

Herschel's grindstone and Kapteyn's star system were too small because

they did not know about interstellar dust clouds.

Although neutron stars are very hot, they are not easy to locate because

they have small surface areas.

An atom that has lost an electron is called an ion.

true

Blue stars are emit most of their energy at shorter wavelengths than red stars..

true

Blue stars are hotter than red stars.

true

Hydrogen alpha is the longest wavelength Balmer line.

true

Isotopes of the same element have the same number of protons.

true

The hotter an object, the more blue it appears.

true

An irregular galaxy contains

upper and lower main sequence stars and gas and dust.

The first scientific attempt to map the Milky Way galaxy

was completed by William and Caroline Herschel.

The cosmic background radiation comes from the time in the evolution of the universe

when electrons began to recombine with nuclei to form atoms.

The corona of the sun can be observed

with a coronagraph.

A filtergram is a photograph of the sun's surface made

with only those photons emitted in a specific spectral line.

The Great Wall

is a filament of superclusters of galaxies.

If a light-emitting object is moving away from you, you observe its wavelengths to be ________ its wavelengths if it were at rest..

longer than

Which of the following is not evidence of the existence of an interstellar medium?

molecular bands in the spectra of cool stars

An E galaxy contains

mostly lower-main sequence stars and giants.

At extremely high densities and temperatures, electrons can be forced to fuse with protons. This reaction produces

neutrons and neutrinos.

The resolution of Olbers' paradox suggests that it gets dark at night because the universe is

not infinite in age.

Most of the light we see coming from the sun originates in the

photosphere.

The variation in the strength of the calcium H and K emission from sun-like stars implies that these stars

probably have a magnetic cycle similar to the sun's.

The density of a ____ is greater than the density of a ____.

pulsar, white dwarf

Which of the following is not a characteristic of the stars of the disk component of our galaxy?

randomly inclined orbits

Voids are

regions in the universe that separate the filaments of superclusters.

High temperatures are required to get H nuclei to fuse because they ____ one another because of their ____ electric charges.

repel, positive

Granulation is caused by

rising gas below the photosphere.

Compared with the spectral lines in the solar spectrum, lines in a supergiant spectrum are

sharper

The Doppler effect states that the motion of any object can

shift the wavelength of spectral lines.

Sunspots

show the Zeeman effect indicating the presence of strong magnetic fields.

The sky appears blue during the day because

small dust particles in the atmosphere scatter blue light more efficiently than red light.

The ____ is(are) the hot gases that are the moving extension of the sun's corona.

solar wind

There is a mass-luminosity relation because

stars support their weight by making energy.

The radio lobes that flank some radio galaxies produce mainly

synchrotron radiation.

We know that the central object in a planetary nebula has a surface temperature of at least ____ because the nebula contains large amounts of ionized hydrogen.

25,000 K

A typical planetary nebula will be visible for about

50,000 years.

____ occurs when most of the material collapsing to form a protostar has fallen into a disk around the star, and a strong wind from the warm protostar ejects material from its poles.

A bipolar flow

In some regions of the corona, the magnetic field does not loop back to the sun, and the gas escapes unimpeded. These regions are called ____ and are believed to be the source of the solar wind.

coronal holes

The absorption lines in the visible portion of the spectrum of a star that are produced by hydrogen are from the

Balmer series.

How can the coronal gas occupy most of the space but represent only 5% of the mass?

It has a much lower density than the other components.

____ are small luminous nebulae excited by nearby young stars.

Herbig-Haro objects

The extinction of starlight due to the interstellar medium I. is the greatest in the ultraviolet. II. is the greatest in the infrared. III. is caused by ionized hydrogen. IV. is caused by dust particles

I & IV

Giant stars are I. more luminous than the sun. II. larger in diameter than the sun. III. cooler than B stars. IV. located above the main sequence stars in the H-R diagram

I, II, III, & IV

____ galaxies contain large clouds of gas and dust, both young and old stars, but have no obvious spiral arms or nucleus.

Irregular

____ occur(s) because photons we receive from the edge of the solar disk are emitted further from the base of the photosphere than the photons we receive from the center of the solar disk.

Limb darkening

The absorption lines in the ultraviolet portion of the spectrum of a star that are produced by hydrogen are from the

Lyman series.

The bluer the light, the ____ each photon contains.

More energy

The absorption lines in the infrared portion of the spectrum of a star that are produced by hydrogen are from the

Paschen series.

Which of the following could NOT be used as a distance indicator for galaxies?

Planets in our own Solar System

What is the order of star colors with increasing temperature?

Red, Yellow, Blue

The center of our galaxy lies in the direction of the constellation of

Sagittarius

A plot of the continuous spectra of five different stars is shown in the figure below. Based on these spectra, which of the stars is the hottest?

Star A

Each element has its own set of characteristic absorption lines because

electron energy levels differ for each element.

Interstellar gas clouds may collapse to form stars if they

encounter a shock wave.

The energy emitted from the surface of a main sequence star is ____ the energy generated in the core.

equal to

To an observer on Earth, dust in the interstellar medium will cause a star to appear

fainter and cooler than it really is.

An absorption spectrum is also called a bright line spectrum.

false

The Lyman series lines of hydrogen all lie in the infrared.

false

The nucleus of the hydrogen atom consists of a single neutron.

false

The energy generated by the sun is released by the ____ to make ____ nuclei.

fusion of H nuclei, He

The presence of forbidden lines in the spectra of emission nebula indicates that the

gas in the nebula has a very low density.

Elements such as iron, calcium, and titanium are less abundant in the interstellar medium than in the sun. This is most likely due to these elements

having condensed to form dust grains.

Fusion is promoted in the core of the sun by the ____ there.

high temperature and high density

Which of the following is not a fundamental component of the atom?

ion

The hot gas of a radio lobe could be held together by

collision with the intergalactic medium.

The spectra of the coolest stars contain strong absorption features (or lines) of

TiO molecules

Most of the energy emitted by the sun is generated in the

core

Neutrinos are created in reactions in the ____ of the sun.

core

The central galaxy in a double-lobed radio source is usually

a giant elliptical galaxy.

Head-tail galaxies are

a, b, and c

The density of a neutron star is

about the same as an atomic nucleus.

Energy can flow outward from the cores of different kinds of stars by

all of the above

A group of 10 to 100 stars that formed at the same time but are so widely scattered in space their mutual gravity cannot hold them together is called

an association.

The centers of granules

are hot material rising to the photosphere from below.

Spicules

are visible in filtergrams of the solar chromosphere.

In the core of a main sequence star, gas pressure ____ the weight of the overlying materials.

balances

The free-fall contraction of a molecular cloud

can be initiated by shock waves from supernovae.

A white dwarf is composed of

carbon and oxygen nuclei and degenerate electrons.