Astro 7N Unit 2

Question 1

Who proposed the Sun-Centered (Heliocentric) Model of the Universe?

Answer 1

Copernicus

Question 2

What is the distance between the Earth and the Sun?

Answer 2

1 “Astronomical Unit”

Question 3

How long does it take for the Earth to orbit the Sun?

Answer 3

1 year

Question 4

What is Keplers 1st Law?

Answer 4

The planets orbit the Sun in elliptical orbits with the Sun at one focus

Question 5

What is Keplers 2nd Law?

Answer 5

a planet’s speed is fastest when the planet is closest to the Sun (at a point called perihelion), and slowest when it is farthest away (aphelion)

Question 6

What is Keplers 3rd Law?

Answer 6

P^2 = a^3
, where P is the orbital period (a planet’s year, given as a multiple
of Earth years) and a is the semimajor axis (average distance from Sun, given in AU)

Question 7

What is an Aurora?

Answer 7

solar wind particles hit atmospheric gas and lead to emission of different colors;

Question 8

What is the Greenhouse Effect?

Answer 8

Energy from Sun heats Earth. Earth’s surface radiates this heat back towards space by giving off infrared radiation

Question 9

What is the Kuiper Belt?

Answer 9

disk-shaped region beyond Neptune, ranges 30 – 55 AU, contains several dwarf planets

Question 10

What is the Oort Cloud?

Answer 10

houses long-period comets, out beyond the Kuiper belt

Question 11

What are the three criteria for an object to be considered a planet?

Answer 11

1. orbit the Sun (not be a moon around another object);
2. be massive enough to be nearly round;
3. clear the region around its orbit (Pluto does not; many other objects there)

Question 12

The Formation of the Solar System…

Answer 12

1. the Solar System formed 4.5 billion years ago
2. starting with cloud of gas and dust, it collapses due to its own gravity
3. as it collapses, the spinning cloud flattens and forms a disk
4. the Sun forms at center
5. “lumps” in the disk become planets
6. the regions around these proto-planetary clumps clear out (or material is absorbed)
7. only rocks and metals survive in inner region; outside, ices and gases also survive
8. takes a few tens of millions of years to form 11

Question 13

What is the order of the planets going outward from the Sun?

Answer 13

1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune

Question 14

Describe Comets

Answer 14

1. A few kilometers in size
2. Tails pointing away from the Sun develop due to the solar wind
3. Made of ice (both water ice and “dry ice”) and dust — remnants of Solar System formation

Question 15

Describe Asteroids

Answer 15

1. rocks left over when the planets formed
2. many are in the “Asteroid Belt” between Mars and Jupiter

Question 16

Describe Meteors

Answer 16

1. streak across the sky very quickly — they are also called “shooting / falling stars”
2. most meteors are tiny dust particles or grains — less than a centimeter in size — that rapidly burn up in Earth’s atmosphere;

Question 17

Describe Mercury

Answer 17

grayish color, craters, similar to Earth’s moon, but does not have prominent maria, the dark “seas,” like the Moon does

Question 18

Describe Venus

Answer 18

Bright, yellowish, and cloud-covered (no sharp surface features visible). A clue that this is not a gas giant is that it does not have rings, which all gas giants (aka “Jovian planets”) in our Solar System have

Question 19

Describe Earths Moon, Luna

Answer 19

Grayish and cratered, and with distinctive large dark maria, the
remains of old lava flows that covered large patches of its surface

Question 20

Describe Mars

Answer 20

Mars is the color of rust, whitish ice caps at its poles, many craters, some prominent old volcanoes, some large valleys, but no significant surface water

Question 21

Describe Vesta, an asteroid

Answer 21

non spherical

Question 22

Describe Jupiter

Answer 22

Distinctive stormy stripes, cloud bands in different colors (red or brown, to white or even blue-ish). Also has the Great Red Spot, an Earth-sized circular storm in its southern hemisphere.

Question 23

Describe Saturn

Answer 23

Large ring system. Central planet tan-colored and has long-stretched cloud bands, but less color contrast between them as on Jupiter

Question 24

Describe Titan, Saturn’s Moon

Answer 24

Saturated orange color (as opposed to Venus’ pale yellow).
Complete cloud cover; cannot see sharp surface features. Like with Venus, the lack of rings is a hint to help not mistake this for a gas giant.

Question 25

Describe Uranus

Answer 25

Distinctive deep blue-green color. Generally few visible cloud features. A wide ring system, but the individual rings are very dark and thin, with clear gaps between them (compare to Saturn’s). Also, it is tipped nearly on its side, compared to other planets

Question 26

Describe Neptune

Answer 26

Dark and deep blue in color. A few visible dark storm and cloud features. A smaller ring system than Uranus, with just a few thin dark rings

Question 27

Describe Pluto

Answer 27

a tiny “icy dwarf,” it orbits the center of gravity of its system with the proportionally-large moon, Charon