astrophysics ✓ Flashcards
(23 cards)
what is the universe made up of ?
a large collection of billions of galaxies
what is a galaxy made up of ?
a large collection of billions of stars
what is our country’s solar system called ?
Milky Way
what does a moon do ?
orbit planets
what do planets do ?
orbit stars
what do satellites do ?
orbit the Earth or planets
what do comets do ?
orbit stars
what do moons and planets follow on their orbits ?
roughly circular orbits
what speed does a moon or planet orbit at ?
constant speed
what are the orbits of the comets ?
- highly elliptical
- travels fastest when it is closest to the star
- where the gravitational attraction is strongest
what are the units for orbital speed ?
metres (distance) per second
m/s
how are stars classified ?
- according to their colour
what is an an acronym for the stellar classification ?
Oh Boy A Fit Guy Kissed Me
what are the orders of the colours for stellar classification ?
O - blue B - blue A - blue F - blue - white G - white - yellow K - orange - red M - red
what is the colour of a star related to ?
its temperature
what is the life cycle of a massive star ?
- nebula
- protostar
- main sequence
- red supergiant
- super nova
- neutron star
- black hole
what is the life cycle of a small star ?
- nebula
- protostar
- main sequence
- red giant
- white dwarf
- black dwarf
what is a nebula ?
a cold of dust and gas
what is a main sequence star ?
it is the stable period when outwards pressure caused by thermal expansion balances the force of gravity pulling everything inwards.
what is a red giant ?
the hydrogen in the core begins to run out. the star is compressed until it it dense and hot enough that energy created makes the outer layers of the star expand
what is a white dwarf ?
a small to medium sized star becomes unstable and ejects the outer layer of dust and gas leaving a hot dense solid core which is the white dwarf
why does the gravitational field strength vary ?
it varies according to the mass of an object
what is the equation for orbital speed (given in exam) ?
orbital speed = 2π x orbital radius ÷ time period
