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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

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