Star
- a large glowing ball of gas generating light and heat from the nuclear fusion in its core
Planet
- a moderately large object that orbits a star and shine primarily by reflecting light from a star.
3 criteria for a planet: 1) orbits a star; 2) is large enough to have a gravity poll to make it round (in shape); 3) has cleared most objects from its orbital path*
*that’s why Pluto is only a dwarf planet
Constellation
A regional of the sky with recognizable borders that form patterns (88 constellations fill the entire sky)
NB: every star belong to a constellation
Moon
An object that orbits a planet
Asteroid
A relatively small rocky object that orbits a star (a small solar system body)
Comet
A relatively small ice-rich object that orbits a star (a small solar system body)
Small solar systems body
An object that orbits a star but is too small to qualify as a planet (asteroids, comets etc.)
The Universe expansion
An increase in the average distance between galaxies as time progresses
It was found that the expansion accelerates with time
The farther a galaxy is, the faster it is moving away (ll with raisin cake)
The faster the expansion, the younger the Universe (Hubble’s Law)
AU
Astronomical union = the average distance between Earth and the Sun (~ 150 mill km = 1.5*10^8)
Light year
The distance light travels in a year (NOT TIME but distance) (~ 10^13 km)
Axis tilt
-an amount at which the Earth’s axis titles in respect to a line perpendicular to the ecliptic plane (= 23 1/2 *C)
Supercluster
- the largest structure known in the Universe, consisting of galaxy clusters, galaxy groups, individual galaxies (we are in a supercluster called Lineakea)
Local Group
- a group of galaxies (around 50 galaxies), which the Milky Way Galaxy belongs to
Galaxy
A great island of stars, all held together by gravity and orbiting a common center
Solar system
A star with all materials orbiting that particular star, including its planets, moons, comets, asteroids
The process of star formation
Gravity compresses the material in a cloud —> to the point at which the center becomes dense and hot enough —> to generate energy by nuclear fusion —> a star
—> it explodes = dies —> elements from the explosion go to outer space —> mix —> new stars
~ recycling process
Rotation
The spinning of Earth around its axis. Happens from west to east. Every day
Ecliptic plane
An imaginary flame plane representing the Earth’s orbit around the Sun
Dark matter
Matter that we infer to exist from its gravitational effects but from which we haven’t detected any light.
Dark matter apparently dominates the total mass of the universe
Dark energy
It’s the name given to unseen influence that causes the expansion of the universe
The universe
The sum total of all matter and energy; that is everything within and between all galaxies over cosmic time
Does not have a certain center
Summery of speeds
~~Earth rotation - 1000 km/hr
~Earth orbits the Sun at about 100,000 km/hr
~~Solar System moves towards nearby stars at 70,000 km/hr
~The M.W. Rotates at about 800,000 km/hr
~~M.L. Moves towards other galaxies at about 300,000 km/h
