Questions for summative

Question 1

1. What is a galaxy?

Answer 1

A galaxy is a large group of stars, gas, and dust held together by gravity.
Every galaxy has the same elements, forces, and types of energy that are found in our
Solar System

Question 2

Where is earth in the universe?

Answer 2

The Earth is located in our Solar System. The Solar System is located inside the Milky
Way galaxy. Our galaxy is located inside a cluster of galaxies called the Local Group. The
Local Group is located inside a supercluster of galaxies called the Virgo Supercluster

Question 3

What is a supercluster?

Answer 3

A supercluster is a group of galaxy clusters typically consisting of 3 to 10 clusters and spanning as many as 200,000,000 light-years.

Question 4

What is the name of our supercluster and how many galaxy clusters does it contain?

Answer 4

Our supercluster is called the Virgo supercluster and it contains 2 galaxy clusters (the Virgo cluster and the Local group)

Question 5

What are the three types of galaxies?

Answer 5

Spiral galaxies, elliptical galaxies, and irregular galaxies

Question 6

What is unique about elliptical galaxies?

Answer 6

Elliptical galaxies contain mostly older stars.

Question 7

What is cosmology

Answer 7

The study of how the universe began, how it continues to change, and what it is made of is called cosmology.

Question 8

Describe the steady state model

Answer 8

Universe always was and will be the same
The universe expands and new matter is created.
density of the universe in a steady state.

Question 9

Describe the oscillating model

Answer 9

universe formed then expanded. universe expanding now.
When all the energy after the Big Bang is used rate of growth will start slowing down.
universe will contract and shrink.
collapse of the universe then lead to formation of new universe
process will begin again

Question 10

Describe the Big Bang theory model.

Answer 10

The universe begun with a “big bang” and has been expanding ever since.
The big bang was not an ordinary explosion of matter, but a fast expansion of space.
Matter and energy cannot be created, so the density of the universe decreases as it
expands.
The temperature of the universe decreases as it expands.
The universe begun from a small very dense point, called a singularity

Question 11

Describe the Doppler effect and red shift

Answer 11

As light or sound approaches, wavelengths shorter, frequencies
higher.
As it moves away, wavelengths become longer, frequencies
are lower.
This means that:
If a star is moving toward Earth, the light waves/wavelengths of light get shorter.
If a star is moving away from Earth, the light waves/wavelengths of light get longer.
Blue-violet light waves are shorter than red light waves.
This means that:
As a star moves toward Earth, the wavelengths of light are compressed causing a blue
shift.
As a star moves away from earth, the wavelengths of light are stretched causing a red
shift.

Question 12

Describe Edwin Hubble’s discoveries.

Answer 12

1. measured Doppler effect in the light emitted from 25 galaxies outside of the Local Group. light from these galaxies exhibited a redshift. meaning these galaxies are moving away from Milky Way.
2. the redshift of very distant galaxies is not only due to Doppler effect, but also caused by the stretching of space as the universe expands. The universe is expanding, the expansion stretches light traveling through space in a phenomenon known as cosmological redshift or the Hubble
   redshift.
3. Since all galaxies are now moving away from Earth, then they must have originated from the same place. The Universe had a beginning.
4. The redshift of a galaxy depends on its distance from Earth.
   The farther away a galaxy is, the faster it is moving away – Hubble’s Law.

v = H∙d

Question 13

Are there limitations to Hubble’s law?

Answer 13

Hubble’s Law only works for distant galaxies. For nearby galaxies (in the Local Group), stars inside the Milky Way, and for objects in our Solar System, the relationship between distance and velocity does not hold

Question 14

.List the timeline of the formation of the universe. How old is the universe?

Answer 14

Big Bang and inflation
* universe takes shape.
* Basic elements are formed
* Atoms form.
* Stars and galaxies form.
* Sun and Earth form.
The universe is about 13.7 billion years old.

Question 15

.Which theory is supported by the image taken by the WMAP? What other evidence did we obtain from the WMAP?

Answer 15

supports the Big Bang Theory as it depicts the temperature of the radiation left over from the Big Bang, when universe was young
The age of the universe is 13.7 billion years.
The universe is flat (± 0.4% error).
The composition of the early, dense universe was 63% dark matter and 27% normal matter.

Question 16

15.What is dark matter?

Answer 16

Dark matter is an invisible form of matter that does not emit any detectable electromagnetic energy of its own. Dark matter can only be detected by the gravitational effects on ordinary forms of matter in the universe.

Question 17

How are galaxies formed?

Answer 17

Galaxies form when dense regions of dark matter clump together. This is why there are places full of galaxies (filaments) and places empty of galaxies (voids).

Question 18

What is dark energy?

Answer 18

Dark energy is an unseen form of energy which causes the expansion of the universe