Definitions Week 1

Question 1

Galaxy Clusters

Answer 1

Groups of galaxies with more than a few dozen large members

Question 2

AU - Astronomical Unit

Answer 2

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

Question 3

One light year

Answer 3

Distance. 10 trillion kilometers or six trillion miles

Question 4

Speed of light

Answer 4

300000 kilometers per second

Question 5

Planet

Answer 5

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

Question 6

Dwarf planet

Answer 6

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

Question 7

Moon

Answer 7

An object that orbits a planet.

Question 8

Satellite

Answer 8

Use generally to refer to any object orbiting another object

Question 9

Asteroid

Answer 9

A relatively small and rocky object that orbits a star

Question 10

Small solar system body

Answer 10

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

Question 11

Solar system

Answer 11

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

Question 12

Star system

Answer 12

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

Question 13

Galaxy

Answer 13

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

Question 14

Cluster (or group) of galaxies

Answer 14

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

Question 15

Supercluster

Answer 15

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

Question 16

Universe, or Cosmos

Answer 16

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

Question 17

Observable universe

Answer 17

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

Question 18

Rotation

Answer 18

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

Question 19

Orbitz (revolution)

Answer 19

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

Question 20

Expansion of the universe

Answer 20

The increase in the average distance between galaxies as time progresses

Question 21

Age of the universe

Answer 21

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

Question 22

When did Pluto become a dwarf planet

Answer 22

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

Question 23

Alpha Centauri

Answer 23

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

Question 24

Number of stars in the Milky Way galaxy

Answer 24

More than 100 billion

Question 25

How many galaxies in the observable universe

Answer 25

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

Question 26

Birth of the universe

Answer 26

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

Question 27

What two chemical elements did the early Universe contain

Answer 27

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

Question 28

When was our solar system born

Answer 28

Four and a half billion years ago

Question 29

Does everything in the universe expand

Answer 29

No, individual galaxies and the Galaxy clusters do not expand

Question 30

How are stars born

Answer 30

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

Question 31

When does a star die

Answer 31

A star dies when it exhausts its usable fuel

Question 32

Supernovae

Answer 32

When the most massive stars die in a Titanic explosion called a supernova

Question 33

What happens when stars explode

Answer 33

The supernova blows out matter that mixes with other matter floating between the stars in the galaxy, eventually becoming part of new clouds of gas and dust for which more stars are born

Question 34

What are we made of and where did it come from

Answer 34

We and Earth are made primarily of other elements such as carbon nitrogen oxygen and iron. Those elements were manufactured by stars

Question 35

What is the cosmic calendar

Answer 35

the cosmic calendar compresses the 14 billion year history of the universe into one year so they each month represents a little more than 1 billion years

Question 36

What direction does the Earth rotate and orbit

Answer 36

Counterclockwise as viewed from the North Pole

Question 37

Elliptic plane

Answer 37

Earth's orbital path defines a flat plane that we call the elliptical plane

Question 38

Earth's axis tilt

Answer 38

23 and a half degrees from the line perpendicular to the elliptic plane

Question 39

How often does our solar system rotate around the center of the Galaxy

Answer 39

Every 230 million years

Question 40

Dark energy

Answer 40

dark energy that astronomers first recognized when they discovered that the expansion of the universe is actually getting faster with time and the scientists have found to make up the majority of the total energy content the universe

Question 41

How do galaxies move within the universe

Answer 41

the billions of galaxies in the universe move relative to one another. Within the local group some of the galaxies move towards us some move away from us and numerous small galaxies apparently orbit our Milky Way galaxy

Question 42

Edwin Hubble discovered

Answer 42

every galaxies outside the local group is moving away from us. The more distant the Galaxy the faster it appears to be racing away