Astro 7 Unit 4 Review

Question 1

Give a 5-minute history of the Universe

Answer 1

1. Big Bang
2. Quarks form
3. Quarks bind together into protons and neutrons
4. Protons and neutrons bind together to form helium nuclei
5. Electrons join with nuclei to form complete atoms
6. Stars and galaxies start to form via gravity
7. The first large stars die, and spread elements heavier than hydrogen and helium
8. Quasars light up at the centers of many forming galaxies, as nearby fuel feeds the supermassive black holes
9. Our Sun and Earth form about 4.5 billion years ago
10. First mammals and dinosaurs appeared on Earth 225 million years ago
11. Humans began to roam the Earth just over 100,000 years ago

Question 2

What are the different types of galaxies?

Answer 2

Spiral galaxies - can have a central bar, in which case they are “SB” galaxies — or not, in which case they are “S” galaxies
Elliptical galaxies - range from E0 (circular) to E7 (elongated) depending on their shape on the sky

Question 3

What is matter composed of?

Answer 3

Quarks - 6 types of quarks and 6 anti-quarks
Leptons - include electrons and neutrinos, 6 types of leptons and 6 anti-leptons
Bosom - exchanged between particles in order to make the forces work, 6 types

Question 4

How were galaxies different in the past than at present?

Answer 4

very hot and dense. All matter and energy in our observable universe
was then compressed into a single point of space

Question 5

How do we know that dark matter exists, and what do we know about its nature?

Answer 5

unknown element, invisible except for its gravitational influences, galaxies are rotating faster without the mass to account for it (therefore dark matter is in play)

Question 6

What are the three major parts of the Milky Way Galaxy (and other spirals)?

Answer 6

Bulge - older, spherical region in the center of the disk
Disk - young, 100,000 light years in diameter — spiral pattern
Halo - older, larger, spherical region around whole galaxy;

Question 7

What different kinds of objects are present in the Milky Way Galaxy?

Answer 7

star clusters, planetary nebulae, nova, supernova, star forming regions, galactic center,

Question 8

Universal Composition

Answer 8

4.6 % atoms, 24 % dark matter, and 71.4 % dark energy

Question 9

Dark Energy

Answer 9

type la supernova are ‘candles’, relationship between the apparent brightnesses and redshifts for Type Ia
supernovae can be used to measure the geometry of space

Question 10

Observations from la supernova are that the universe…

Answer 10

is accelerating its expansion

Question 11

What is a redshift?

Answer 11

shifting of the lines in the spectrum of an object to longer wavelengths (to redder colors), due to its motion away from the observer.
(alternatively, “blueshift” would be seen for an object moving towards the observer)

Question 12

What is Hubble’s law?

Answer 12

distances to galaxies can also be crudely estimated, constant is effectively the expansion rate of our universe

Question 13

How many galaxies are there?

Answer 13

50-100 billiob