astrophysics

Universe: Large collection of billions of galaxies.
Galaxy: A large collection of billions of stars. our solar system is in the milky way galaxy

Everything that orbits the sun, including planets, dwarf plants, asteroids, and comets.

Large object which orbits a star in a slightly elliptical orbit.
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
Dwarf planet

Planet-like object that isn't big enough to be a planet. pluto
An object which orbits a planet in a slightly elliptical orbit

Natural: An object which orbits a planet that is not man-made
Artificial: An object which orbits a planet that is man-made.
Both have circular orbits, slightly elliptical

Asteroid: Lump of rock and metal that orbits the Sun. lots in asteroid belt
Comet: Lump of ice and dust that orbits the Sun, usually in a highly elliptical orbit. Travel faster when closer to the Sun because of increased pull of gravity

Planets move around the sun and are constantly changing direction/accelerating.
Instantaneous velocity keeps it accelerating and gravitational potential keeps the planets around the sun in an orbit

Mass and distance
the larger the mass the stronger the gravitational field
The closer you get to a planet the faster you need to go to remian in orbit

Artifical earth satellites that have an orbital period of one day useful in communication

v = 2πr/T

Color of a star depends on the visible light it emits and its surface temperature determines the frequency
A red star - coolest, emits lowest frequency light
A blue star- emits highest frequency light

depends on size and temperature
Absolute magnititude - measure of how bright a star would be a fixed distance from earth. Lower absolute magnitude, brighter the star. +5 of Sun

A diagram that shows the stars(main sequence, giant, supergiant, and dwarf) with their temperature against brightness (absolute magnitude).

nebula → main sequence → red giant → white dwarf

nebula → main sequence → red supergiant → supernova → neutron star (or black hole if very large)

A cloud of dust and gas.

Gravity pulls dust and gas together to form protostar, temp rises as the star gets denser and more particles to collide. High enough temp for nucleus fusion, hydrogen nuclei undergo nuclear fusion to form He nuclei. Energy is released and keeps the core hot

The long, stable period of a star's cycle, where the gravitational forces are balanced by the outward pressure of energy from the fusion of hydrogen.

For a star much bigger than the Sun, the hydrogen in the core runs out, gravity is greater than the thermal expansion. Star compresses until it becomes hot enough to make outer layers expand. Red supergiant formed if larger than sun and red giant formed if similar size to sun. Red because surface cools

a star about the mass of the Sun (red giant) becomes unstable and ejects its outer layers of dust and gas, leaving a hot, dense, solid core.

For a star greater than the Sun, glow brightly as they undergo more fusion to make heavier elements. Expand and contract several times as the balance shifts between gravity and thermal expansion. Eventually, explodes into supernova.

The exploding supernova throws the outer layers of dust and gas into space, leaving a dense core called a neutron star.

The very dense core was left behind after a supernova of a very massive star will collapse and become a blackhole