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.
