astronomy test 4

the gas and dust between stars is made mostly of

hydrogen and helium

the gas and dust between stars is called the

interstellar medium

as a start begins to form from collapsing gas, before fusion has begun, its thermal energy comes from

gravitational potential energy

before fusion has begun a forming star is called a

pre main sequence star

when two clouds of gas collide and heat up enough to emit light they have become

an emission nebula

when a star begins to form, it is first blocked from view inside a

bok globule

if a star is not massive enough to begin fusion it becomes a

brown dwarf

stars in open clusters are

not gravitational bound, metal rich and young

stars in globular clusters are

gravitationally bound metal poor and old

we can find the age of an open cluster by plotting its stars on an hr diagram and

observing the mass of the stars that have most recently joined the main sequence.

we can find the age of a globular cluster by plotting its stars on a hr diagram and

observing the mass of the stars that are just beginning to turn off the main sequence.

as a star slowly moves through the instability strip on the hr diagram it

displays regular variations in brightness

globular clusters are often found

outside the plane of the galaxy

cepheids have a simple relationship between t

luminosity and period of brightness variation

a roche lobe is

the region outside of which a binary star can not hold onto material

in a low mass star(0.08 earth masses to 0.4 earth masses) fusing hydrogen in its core

helium leaves the core through convection bringing in more hydrogen from the rest of the star

when a low mass star runs out of hydrogen for fusion it

just sits there

the core of an intermediate mass star (0.4 earth masses to 8 earth masses) fills up with helium over time because

they are not convective so the helium stays where it is produced

when hydrogen in the core of an intermediate mass star runs out the star shrine until

hydrogen fusion begins in a shell around the core

in intermediate mass stars of less than 2 earth masses a helium flash occurs because

helium fusion begins in a core held up by electron degeneracy pressure, which does not depend on temperature

at the end of an intermediate mass stars life

most of its mass is blown into space as fusion sputters to a halt and ions recombine

what is left of the core of an intermediate mass star os a

white dwarf

high mass stars (more than 8 earth masses) are able to

fuse a series of high mass stars life it has a core of

in the final stage of a high mass stars life it has a core of

iron because fusion beyond iron consumes rather than releses energy

at this point fusion in shells around the core adds mass to the core until

the core begins to collapse until it rebounds and the star explodes as as type II supernova

what remains of core of many high mass stars is

a neutron star

a white dwarf is composed of

carbon and hydrogen

a white dwarf is held up against gravitational collapse by

electron degeneracy pressure

a white dwarf in a binary system will become a nova if

it accretes enough hydrogen for fusion to occur on its surface

a white dwarf in a binary system will become a type Ia supernova if

it gains enough mass that carbon fusion begins rapidly in its interior

a white dwarf is about the size of

the earth

a neutron star is held up against gravitational collapse by

neutron degeneracy pressure

a neutron star is about the size of

cortland

cosmic rays from supernovae are

high pressure protons electrons and positrons flying through space.

a pulsar is a

rotating neutron star with a strong magnetic field

an x-ray burster is observed when

helium builds up on a neutron star until fusion occurs on the surface

if a neutron star gains mass unit it is more than 3 earth masses it will

collapse and become a black hole

a glitch in the period of a pulsar in which the period suddenly get slightly shorter is caused by

a reshaping of the neutron stars crust

if the spectrum of a supernova shows hydrogen absorption lines it is a

type II supernova

to be a black hole something must

be dense enough to create an event horizon

a black hold can be characterized by just three quantities

mass angular momentum and charge

a Kerr black hole is a black hole that

rotares

a Schwarzschild black hole is a black hole that

does not rotate

as you fall through the event horizon of a black hole you will notice

nothing special

Hawking radiation causes black holes to

slowly loose mass

a kilo nova occurs when

two neutron stars collide

a kilonova can be detected because it emits

visible light gamma rays and gravitational waves

we detect black holes indirectly as

absorption nebula