-
The temperature of the sun's core
15 million degrees
-
what are sunspots
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
hydrogen
-
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
massive stars
-
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?
doppler shift
-
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?
blue star
-
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
distance
-
the most intense wavelength (color) of a main sequence star is, inversely proportional to the star
temperature
-
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
open cluster
-
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?
t-tauri
-
what is the nature of the process that causes stars to radiate heat and light for millions or billions of years?
nuclear
-
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
white dwarf
-
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
black hole
-
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?
gravity
-
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?
10-100
-
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
thousands
-
in what band is there extreme high energy radiation from the center of the galactic nucleus?
xrays
-
the region between the stars is filled with
- hydrogen molecules
- co, co2, h20, nh3, ch4, he...
-
if we see a blue nebula near a blue star, what kind of nebula is it?
reflection
-
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
molecular hydrogen
-
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
jets
-
double-lobed radio structures, exceptionally bright nuclei (in radio & xray) and very high doppler recession velocities are often features of active galaxies and also
quasars
-
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
quasars are only very far away
|
|
