Astrophysics Flashcards
The universe is
a large collection of billions of galaxies
A galaxy is
a large collection of billions of stars
A solar system is
a collection of planets orbiting a common star
Our solar system is
the Milky Way galaxay
Gravitational field strength is
force per unit mass on a body in a gravitational field
Gravitational field strength units
Newtons per kilogram (N/kg)
Weight (W) equals
mass x gravitational field strength (mg)
Gravitational force enables…
…bodies to orbit around another body.
Moons orbit
planets
Planets and comets orbit
the sun
Orbital paths or moons and planets are
slightly elliptical
Orbital speeds of moons and planets are
nearly constant
Orbital paths of comets are
highly elliptical
Artificial satellites orbit
the earth
Orbital speed equals
(2 x pi x orbital radius ) / time period
V = (2 pi r)/T
Nearer a star comet’s speed is
greater, because the ice inside them melts as they get closer and warmer, causing their mass to decrease
Stella Evolution
1. A star begins as
2. The particles experience
3. They continue to clump until
4. Hydrogen nuclei
5. This outward pressure
6. The star is now
7. and called a
8. Eventually the hydrogen
9. If the mass of the collapsed star is similar to the sun
10. If the mass of the collapsed star is greater than the sun
- a cloud of dust and gas called a nebula
- a weak attraction to each other a begin to clump together
- the pressure and temperature are great enough for nuclear fusion
- Fuse together to form helium nuclei which releases a large amount of energy and causes great outward pressure.
- balances with the inward pressure due to gravity
- stable
- main sequence star
- in the star is used up so there is no longer enough outward pressure from the nuclear fusion and it collapses.
- it becomes a red giant, then a white dwarf and finally it cools to a black dwarf
- It expands and becomes a red super giant, before exploding in a supernova. What remain is a neutron star or (if it was exceptionally massive) a black hole
Stars can be classified according to
colour
The colour of a star is related to
its surface temperature
Hotter stars are
bluer
Cooler stars are
redder
