dark spots occur where twisted magnetic field lines channel hot gases
what do we learn about the solar interior from solar seismology
densities, temperatures, and composition of inner layers are measured
what is the photosphere
the coolest part of the sun
the sun's corona ejects a solar wind of particles. which partic les
the rainbow of colors (wavelengths) emitted by the sun is an absorption specturm. how can we tell which elements are found in the sun
each element has electrons that absorb/emit unique colors
Which stars spend the shortest time on the main sequence
if a star that is 30 pc away from us has apparent magnitude of 7, would the star's absolute magnitude be greater or smaller than 7
smaller: a smaller magnitude describes a brighter object
stars motion away and toward us are measured differently than motions across our field-of-view. what technique is most used to measure the speed of a star moving away from us?
some stars finish the main sequence in a few million years while others are not finished the main sequence after 10 billion years. which finish the main sequence first?
what describes a spectral binary pair of stars
spectral lines periodically change wavelength due to orbiting of two stars
variable stars periodically change their brightness. Cepheid variable, (CV) absolute magnitude is related to the period of variability. CV's are useful in determining the star's
the most intense wavelength (color) of a main sequence star is, inversely proportional to the star
blue giant stars have huge very hot core and fuse fast. why does main sequence fusion take place only in the core
only the center is hot and dense enough
if a cluster of stars has only 100-1000 stars, loosely held together by gravity, in the disk of our galaxy, and each contains many elements (like our sun) then it is a
how do stars form
gravity collapsed a could of gas/dust into one of more stars
what describes premain sequence not yet stable stars, sometimes with variable erratic intensity or jets?
what is the nature of the process that causes stars to radiate heat and light for millions or billions of years?
what is a brown dwarf?
a low mass object that can't sustain fusion like a star
why are binary stars so common
many stars form due to gravity in dense spots of the same gas clouds
what happens to cause a star to become a red giant
hydrogen fuel becomes too cool and not dense enough to support fusion
gravity collapses the star to a smaller, hotter core
the core comes dense and hot enough to fuse helium
heat causes thermal expansion to a giant size
what happens inside a red giant
the core gets progressively smaller and hotter, fusing more elements
what causes the balance between thermal expansion and gravity to fail in a red giant
iron fusion requires more energy than it radiates
how were earths heavy elements created
nuclear fusion/recycling by stars
a planetary nebula is misnamed because it has nothing to do with planets. where does a planetary nebula come from?
shells of gas are ejected as a stare core collapses to form a white dwarf
describe a white dwarf
as large as earth, supported by electron degeneracy, 1 tspoon=5tons
after the red giant phase, if the stellar core retains less than 1.4 solar masses, the result will be a
a spectacular supernova 1a increases in brightness by 20 magnitudes (a factor of a hundred million) what could cause this kind of supernova
gas mass transfer from neighboring red giant explodes a white dwarf
the core of an imploding type II supernova could become
how do we know that the crab nebula is a supernova remnant
gas filaments are expanding rapidly
what stops the gravitational implosion of a neutron star?
neutrons pushing against neutrons
if neutron stars are too small to be seen, how can we observe them
as they rotate, they emit radio waves along magnetic axes
radio emissions are seen once per star rotation
some neutron stars are sources of pulsar pulses
we can detect a neutron star in a binary pair if a visible star orbits it
if a star collapses and the core has 8 or more solar masses, what prevents heat and light and gas from escaping from the collapsed black hole?
How would we recognize the presence of a black hole
spectroscopic binary star orbiting a massive invisible star
many stars and clouds of gas orbiting a region in a galaxy center
xrays from hot material colliding as it falls through an accretion disc
the schwarzchild radius is 3km/solar mass. what is the even horizan
a distance from a central black hole within which light cannot escape
assume very large uniform cloud rolled up long ago into a massive blue giant star, passing through a red giant stage to form a black hole. what is the maxiumum amount of mass (in solar masses) a black hole could have?
where are the disk stars in the spiral arms of our galaxy going?
revolving around the nucleus
only ancient (old red) stars illuminate which region of the milky way
halo of globular clusters
an open cluster of stars often is found in regions of ionized gas, with some O & B stars. how many stars are in an open cluster
in what band is there extreme high energy radiation from the center of the galactic nucleus?
the region between the stars is filled with
co, co2, h20, nh3, ch4, he...
if we see a blue nebula near a blue star, what kind of nebula is it?
what is interstellar reddening
blue is lost by scattering through dust & gas
describe a globular cluster
old red dwarf stars > 100000 solar masses
since small amounts of carbon monoxide, co are easily detected, we use CO measurements to help identify regions of the most common gas
the most distinguishing features of galaxies are
millions to thousand billions of stars
individual stars are so far apart (compared to their size that collisions are very unlikely. compared to the size of galaxcies, the distance between the centers of galaxies in a cluster...
is small enough that galaxies can merge
explain a starbust galaxy
a very bright agn with blue stars
large spiral galaxies near us are likely to have this at their core.
a black hole
what can an active galaxy have than an ordinary galaxy doesn't have
double-lobed radio structures, exceptionally bright nuclei (in radio & xray) and very high doppler recession velocities are often features of active galaxies and also
how is a quasar different than an active galaxy? only quasars have
extreme doppler shifts
three demensional plots of thousands of clusters galaxies show structure that looks like
formation on edges of voids (bubbles)
hubbles law says
dopple speeds were greatest further away and longer ago
if our galaxy rotates once every 230 million years, how do we detect this motion
proper motion & doppler shifts
on the pitch fork diagram of galaxies, spiral galaxies are classified by
spiral arm length/ width of nucleus
what measurements are best for mapping quasars?
survey of red shifts
what is a quasar
extremely bright core of a galaxy with a huge red shift
quasars are relatively small objects to radiate so much energy. why isnt a quasar seen in our huge galaxy?
our galaxys quasar may have faded
which best describes gravitational lensing
image distortion due to gravitational focusing of light by an intervening galaxy
how do we know that the universe was different billions of years ago