Lecture 3

Question 1

1 AU (Astronomical Unit)

Answer 1

~150 million km

Distance between Sun and Earth

Question 2

1 lyr (light year)

Answer 2

~10 trillion km

Distance light can travel in 1 year

Question 3

Radar ranging

Answer 3

Bounce radio waves of other planets and measure the distance

Good for planets in solar system

Question 4

Parallax

Answer 4

Uses hypotenuse

Good for nearby stars

Question 5

Main-sequence fitting

Answer 5

Uses inverse square law

For things within milky way

Question 6

Cephedes

Answer 6

So bright that they can be seen from other galaxies

Distance to nearby galaxies

Question 7

Distant standards

Answer 7

Used supernova stars that explode to find galaxies

Question 8

How many arcminutes in a degree?

Answer 8

60

Question 9

Red-shift of galaxies

Answer 9

Uses Dopler Effect

Blue-shifter: Getting closer
Red-shifter: Going away

Question 10

Hubble’s Law

v = H x D

Answer 10

Speed of galaxy’s recession is proportional to distance

Question 11

What is the age of the Universe?

Answer 11

T = 1/H = 1/(13.7x10^9 yr)

or 4x10^17 secs

Question 12

Big Bang nucleo-synthesis

Answer 12

1 sec after Big Bang, temp dropped to 10 billion K. Universe wad filled with electrons, protons, neutrons and photons but it was too hot to make atoms.
As it cooled, protons and neutrons fused to make light elements.
After 3 mins, too cold to make more fusion rxns.

Question 13

What elements were created right after the Big Bang?

Answer 13

Hydrogen
Helium
Lithium
Beryllium

Question 14

What produced heavy elements?

Answer 14

Stars

Hot enough for more fusion

Question 15

What are the terrestrial planets?

Answer 15

Mercury
Venus
Earth
Mars

Question 16

What are the giant planets?

Answer 16

Jupiter
Saturn
Uranus
Neptune

Question 17

How does a solar system form?

Answer 17

Gas-cloud collapses and forms a disk, spinning faster.

Central gas ball becomes dense and hot enough to start hydrogen fusion and create the Sun.

Question 18

Planetismals

Answer 18

Solid, forms very quickly (few Myr)

Question 19

Theory for moon formation

Answer 19

Planetismal crashed into young Earth.

Earth spins fast and becomes molten. A part of the crust broke off to form the moon.

Question 20

Hot Jupiters

Answer 20

Jupiter-like planet found close to the sun.

May have formed far out but orbital migration pulled it closer as it grew.

Question 21

2 theories of planet formation

Answer 21

1. Slow - Grow by collisions and accretion

2. Fast - Spiral instability where proto-planet forms

Question 22

Igneous rock

Answer 22

Molten rock which solidifies

Types:
Basalt - Dense, iron and magnesium
Granite - Lighter, silicate admixtures

Question 23

Metamorphic rock

Answer 23

Existing rock formed by high pressure and heat

Question 24

Sedimentary

Answer 24

Gradual compression of sediments

Good for fossils

Question 25

Radiometric dating

Answer 25

Radioactivity decreases in deeper layers because of half-life
(e.g. All expected carbon at the top layer have decayed or turned into a different element in a deep layer)

Question 26

Age of sun and earth

Answer 26

Sun: 4.57 Gyr
Earth: 3.9-4.0 Gyr

Question 27

Eons

Answer 27

Hadean
Archean
Proterozoic
Phanerozoic

Question 28

Era

Answer 28

Subdivision of eon

Question 29

Periods and epochs

Answer 29

Subdivisions of era