47 terms

Astronomy Test IV

parallax of one arc sec-- 3.26 light years
Proper Motion
amount stars moves across the sky, most are too far away to see proper motion
apparent brightness
brightness of a star in night sky
magnitude scale
each magnitude number changes by 2.5 times up or down
absolute mag
how bright a star would appear at 10 parsecs
mass luminosity
the more massive the star the brighter it is
radius luminosity
the more massive the star the brighter it is
visual binaries
can see the two stars and use to get masses
spectroscopic binaries
cannot see the companions but spectrum tells them they are there
spectroscopic parallax
uses HR diagram to measure distance to stars
eclipsing binaries
two stars that block each other's light, easy to measure masses of stars
Main sequence turnoff point
star leaves main sequence as it gets old
molecular clouds
large cool gas cloud that has many materials and dust star formation
forming star
gases ejected as star forms
thermal vs. degenerate pressure
thermal, out, degenerate stops collapse inward
brown dwarfs
failed stars
hydrogen shell burning
older star having fusion moved out from core
white dwarf and planetary nebula
sun dies as core called white dwarf surrounded by planetary nebula
CNO cycle
more massive stars than the sun use this
iron stage
last fuel most massive stars can use
huge explosion, type 1 binary star dearth type II one large star explosion
neutron star
1.4 to 6 solar mass, 10 mile collapsed core of neutrons
electron degeneracy
that which stops white dwarf from collapsing any further
white dwarf
.1 to 1.4 solar masses, sun ends up this way 10000miles across earth size
white dwarf limit
.1 to 1.4
accretion disk
material falling in 10 percent energy production
binary star explosion, periodic
white dwarf supernova
binary stars collapse on each other, type 1
massive star supernova explosion
type II one large star explosion
neutron stars
1.4 to 6 solar mass, 10 mile collapsed core of neutrons
neutron degeneracy
stops further collapse
rotating neutron star
black hole
light cannot escape, 6 solar masses and above
Schwarz child radius
the size of a black hole event horizon
event horizon
once you cross you cannot return
mass but no size
gamma ray bursts
matter falling into black holes giving large explosions of gammas
spiral density wave
theory that the massive black hole in our galaxy sends compression waves through the galaxy and creates a new spirl arm
interstellar medium
material between stars gas and dust
21 cm radiation
hydrogen spin flip, radio waves
dark matter
90 percent of matter in galaxy
cosmic rays
particles shot out by supernova
dust grains
carbon and silicate dust between stars
emission nebula
heated glowing gases
reflection nebula
bluish from dust reflection
molecular clouds
prime areas for formation