Stars Flashcards
more massive stars, due to greater gravity, are..?
squeezed into smaller, more densely packed objects than less massive stars
hottest, brightest and more massive stars
Blue stars
90% of the stairs
Main sequence stars
stars exceeding eight solar masses, with short life spans
High-Mass Stars
Stellar Evolution of Medium-mass (sun-like) stars
Nebular > protostar > main-sequence > red giant > planetary nebula > white dwarf
Red Giant Stage
begins when the hydrogen is consumed, leaving a helium-rich core > core no longer has the gas pressure that resist the inward pull of gravity > core contracts, temperature increase > expansion of the star > as the star expands, its surface cools (red) > eventually the star’s gravity stops expansion > gravity and gas pressure, again achieve balance > star enters a stable state, but is much larger > astonishing increase in temperature, converts helium into carbon and oxygen
largest white dwarfs = ?
least massive
smaller and more massive than white dwarfs
Neutron Stars
“average star”
Sun
radiates short pulses of radio energy named pulsar (pulsating radio source)
Neutron Stars
without fuel ->no balance between gas pressure and gravity > it collapses > enormous implosion resulting in a shock wave > this energetic shock wave blasts the star’s outer shell into space generating ..
SUPERNOVA
terminate in brilliant explosions (supernova)
*during supernova, these stars become millions of times brighter
High-mass stars
terminate in brilliant explosions (supernova)
*during supernova, these stars become millions of times brighter
High-mass stars
*much fainter and smaller than the main-sequence stars of the same temperature
*some are almost the same size of Earth
White Dwarfs
form if the core of a remaining star exceeds the three solar mass limit (neutrons can withstand the gravity)
Blackhole
90% of star-life
Main-sequence stage
some red giants alternately contract and expand
variable stars
Hertzsprung-Russell Diagram
Protostar Stage
gravitational contraction continues rapidly > core heats much faster > temperature: 10 million K > start to initiate nuclear fusion (hydrogen fusion) > will reach a point wherein inward pull of gravity will be balanced by temperature of hydrogen fusion
with masses ranging between 1/2 and eight times that of the Sun
Medium-Mass Stars
Stellar Evolution of Massive Stars
Nebula > protostar > main sequence (blue) > Red supergiants > supernova explosion > neutron star or blackhole
spirals around a “void”
accretion disk
main sequence = ?
active years
electrons are displaced inward from their regular orbits around an atom’s nucleus
Degenerate matter
Why is it called protostar?
heat is not enough to initiate nuclear fusion (source of energy)
coolest, dimmest and less massive stars
Red stars
without sources of energy, white dwarfs..
slowly cool and dim
never become bloated red giants and remain a stable main-sequence star until they ran out of hydrogen fuel and collapse into a white dwarf
Low-mass stars
first black hole to be discovered
Cygnus X-1
Stellar Remnant
* white dwarf
* neutron star
* black hole
found in the center of galaxies are estimated to be millions of solar masses
Larget blackholes (supermassive)
densed, Earth-sized objects
White Dwarfs
stars with 0.5 solar mass
Low-mass stars
have masses 10 times that of the Sun, but are only about 20 miles across
Small black holes
*stars with large radiating surfaces
*appear in the upper right position of H-R diagram
Red Giants
electrons are forced to combine with protons in the nucleus to produce neutrons
Neutron Stars
found in the center of galaxies are estimated to be millions of solar masses
it should become extremely hot and emit a flood of X-rays before it is engulfed
have 10 billion years
Yellow stars (sun-like)
useful tool for understanding Stellar Evolution
Hertzsprung-Russell Diagram
stars experience minimal change in size or energy output (balance maintained)
Main-sequence stage
gases that are pulled from the companion form an accretion disk while emitting a steady stream of X-rays
Black holes
gravitational attraction within a nebula causes..?
cloud to collapse on itself
Stellar Birth
interstellar clouds, rich in gas and dust > gravitational contraction, pulling particles into the center > as the cloud collapses, gravity is converted to thermal energy (increase in temperature)
extremely hot, their surface gravity is so immense that even light cannot escape
Black holes
smallest white dwarfs = ?
most massive
Stellar Evolution of Low Mass Stars
Nebula > protostar > main sequence (red) > white dwarf
>as a red giant, they fuse hydrogen and helium at accelerated rates and once fuel is exhausted, they collapse into a white dwarf
>without a source of nuclear energy, white dwarfs become cooler and dimmer
Medium-Mass Stars
>independently studied the relationship between true brightness (absolute magnitude) and temperature of stars
>astronomers survey a portion of the sky and plot each star according to luminosity
Ejner Hertzsprung and Henry Russell
radiate energy more, depletion of fuel in just few billion years
Blue Stars
Every stage of a star’s life is ruled by..?
gravity
very immense stars
Super giants
have masses 1,000 times the Sun
intermediate black holes
with radius 800 times that of the sun
Betelgeuse
with rising temperature and pressure…
A star is born
radiate energy more, depletion of fuel in just few billion years
Red Stars
smallest white dwarfs were produced from…?
collapse of larger, more massive main-sequence stars
