Definitions Week 1 Flashcards Preview

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Flashcards in Definitions Week 1 Deck (42)
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1

Galaxy Clusters

Groups of galaxies with more than a few dozen large members

2

AU - Astronomical Unit

150 million kilometers or 93 million miles, Earth's distance from the Sun

3

One light year

Distance. 10 trillion kilometers or six trillion miles

4

Speed of light

300000 kilometers per second

5

Planet

Reflects light from its star.

Required to:
1. Orbit a star
2. Is large enough for its own gravity to make it round
3. Has cleared most other objects from its orbital path

6

Dwarf planet

A planet that orbits a star and is large enough for its own gravity to make it around, but has not cleared most other objects from its orbital path

7

Moon

An object that orbits a planet.

8

Satellite

Use generally to refer to any object orbiting another object

9

Asteroid

A relatively small and rocky object that orbits a star

10

Small solar system body

An asteroid, comet, or other object that orbits a star but it's too small to qualify as a planet or dwarf planet

11

Solar system

The Sun and all the material that orbits it including planets, dwarf planets, and small solar system bodies

12

Star system

A star, sometimes more than one star, and any planets and other material that orbit it

13

Galaxy

a great island of stars in space, all held together by gravity and orbiting a Common Center with the total mass equivalent to that of millions, billions, or even trillions of stars

14

Cluster (or group) of galaxies

a collection of galaxies bound together by gravity, small collections of galaxies are generally called groups, well larger collections are called clusters

15

Supercluster

a gigantic region of space in which many groups and clusters of galaxies are packed more closely together than elsewhere in the universe

16

Universe, or Cosmos

The sum total of all matter and energy. That is, all galaxies and everything between them

17

Observable universe

The portion of the entire universe that can be seen from Earth, at least in principle. The observable universe is probably only a tiny portion of the entire universe

18

Rotation

The spinning of an object around its access. For instance Earth rotates once each day around its axis which is an imaginary line connecting the North and South Pole

19

Orbitz (revolution)

The orbital motion of one object around another due to gravity. for example Earth orbits the sun once each year

20

Expansion of the universe

The increase in the average distance between galaxies as time progresses

21

Age of the universe

because the universe is about 14 billion years old, we cannot observe light coming from anything more than 14 billion light years away

22

When did Pluto become a dwarf planet

2006, voted on by the iau when they redefined the definition of a planet

23

Alpha Centauri

The nearest star system to ours, 4.4 light years away.

24

Number of stars in the Milky Way galaxy

More than 100 billion

25

How many galaxies in the observable universe

Roughly 100 billion galaxies in the observable universe. there are as many stars in the observable universe as there are grains of sand on all the beaches of Earth

26

Birth of the universe

Expansion of the universe began with the hot and dense Big Bang. Gravity has pulled matter together to make galaxies

27

What two chemical elements did the early Universe contain

Hydrogen and helium, all other elements were made by stars and recycled from one Stellar generation to the next within galaxies like our Milky Way

28

When was our solar system born

Four and a half billion years ago

29

Does everything in the universe expand

No, individual galaxies and the Galaxy clusters do not expand

30

How are stars born

When Gravity compresses the material in a cloud to the point at which the center becomes dense enough and hot enough to generate energy by nuclear fusion