Oct. 23rd - Intro to Solar System

Question 1

What does the solar system look like?

Answer 1

• Without a telescope, the answer would be “not much.”
• The Sun and planets are so small compared to the distances between them that, viewed from the outskirts of our solar system, the Sun would be just a small bright dot and the planets would be visible only as pinpoints of reflected sunlight
• 4 outlines: Large bodies in the solar system have orderly motions, Planets fall into two major categories, Swarms of asteroids and comets populate the solar system

Question 2

What does the solar system look like?

Large bodies in the solar system have orderly motions:

Answer 2

All planets have nearly circular orbits going in the same direction in nearly the same plane. Most large moons orbit their planets in this same direction, which is also the direction of the Sun’s rotation.

Question 3

Planets fall into two major categories:

Answer 3

Small, rocky terrestrial planets
□ Small in mass and size
□ Close to sun
□ Made of metal and rock
□ Few moons, no rings
Large, hydrogen-rich jovian planets.
□ Large mass and size
□ Far from sun

Question 4

Planets fall into two major categories:

Jovian Planet Make-up

Answer 4

• Made of H, He, and hydrogen components - compounds containing hydrogen, such as water (H2O), ammonia (NH3), and methane (CH4).
• Because these substances are gases under earthly conditions, the jovian planets are sometimes called “gas giants.”
• This term is somewhat misleading however, because except in their outermost layers,* the pressure inside these planets is so high that these “gases” are not actually in the gas phase*; instead, they are compressed into liquid or other high-density forms that behave somewhat differently than any of the usual phases
• Also have rings and many moons

Question 5

Planetary Patterns

Answer 5

• All planetary orbits are nearly circular and lie nearly in the same plane.
• All planets orbit the Sun in the same direction: counterclockwise as viewed from high above Earth’s North Pole.
• Most planets rotate in the same direction in which they orbit, with fairly small axis tilts. The Sun also rotates in this direction.
• Most of the solar system’s large moons exhibit similar properties in their orbits around their planets, such as orbiting in their planet’s equatorial plane in the same direction as the planet rotates.

Question 6

Swarms of asteroids and comets populate the solar system

Vast numbers of rocky asteroids and icy comets are found throughout the solar system, but are concentrated in three distinct regions:

Answer 6

• Asteroid Belt
• Kuiper Belt
• Oort Cloud

Question 7

Swarms of asteroids and comets populate the solar system

Asteriod belt

Answer 7

• Asteroids made of metal and rock, orbit in the asteroid belt between Mars and Jupiter
• Comets: also small objects that orbit the Sun, but they are made largely of ices (such as water ice, ammonia ice, and methane ice) mixed with rock.
• The vast majority of comets never visit the inner solar system. Instead, they orbit the Sun in one of the two distinct regions shown as feature 3

Question 8

Swarms of asteroids and comets populate the solar system

Kuiper belt

Answer 8

ice-rich, beyond Neptune’s orbit

Question 9

Swarms of asteroids and comets populate the solar system

Oort Cloud

Answer 9

comets orbit the sun in the distant, spherical region called the Oort cloud - only a rare few ever plunge into the solar system - a cloud of comets

Question 10

Several notable exceptions to these trends (Large bodies in the solar system have orderly motions, Planets fall into two major categories, Swarms of asteroids and comets populate the solar system) stand out:

Answer 10

Some planets have unusual axis tilts, unusually large moons, or moons with unusual orbits.

For example, while most of the planets rotate in the same direction as they orbit, Uranus rotates nearly on its side, and Venus rotates “backward” (clockwise as viewed from high above Earth’s North Pole). Similarly, while most large moons orbit their planets in the same direction as their planets rotate, many small moons have much more unusual orbits.

Question 11

Planet Overview:

The Sun

Answer 11

• The Sun is by far the largest and brightest object in our solar system
• Contains more than 99.8% of the solar system’s total mass, making it nearly a thousand times as massive as everything else in the solar system combined.
• Looks solid, but actually a sea of hot hydrogen and helium gas (with sunspots)
• Gaseous throughout, temperature and pressure both increase with depth
• The source of the Sun’s energy lies deep in its core, where the temperatures and pressures are so high that the Sun is a nuclear fusion power plant

Question 12

Planet Overview:

Why is the Sun the most influential in the solar system?

Answer 12

• Its gravity governs the orbits of the planets.
• Its heat is the primary influence on the temperatures of planetary surfaces and atmospheres.
• It is the source of virtually all the light in our solar system—planets and moons shine by virtue of the sunlight they reflect.
• In addition, charged particles flowing outward from the Sun make up the solar wind that interacts with planetary magnetic fields and influences planetary atmospheres.

Question 13

Planet Overview:

Mercury

Answer 13

• Mercury is the innermost planet of our solar system, and the smallest of the eight planets
• Because there is virtually no air to scatter sunlight or color the sky, you could see stars even in the daytime if you stood on Mercury with your back toward the Sun.
• You might expect Mercury to be very hot because of its closeness to the Sun, but in fact it is a world of both hot and cold extremes.

Question 14

Planet Overview:

Mercury’s rotation period:

Answer 14

Tidal forces from the Sun have forced Mercury into an unusual rotation pattern:
* Its 58.6-day rotation period means it rotates exactly three times for every two of its 87.9-day orbits of the Sun.
* This combination of rotation and orbit gives Mercury days and nights that last about 3 Earth months each

Question 15

Planet Overview:

Venus

Answer 15

• Venus stood out largely for its strange rotation: It rotates on its axis very slowly and in the opposite direction of Earth, so days and nights are very long and the Sun rises in the west and sets in the east instead of rising in the east and setting in the west.
• We now know that an extreme greenhouse effect bakes Venus’s surface to an incredible 470°C (about 880°F), trapping heat so effectively that nighttime offers no relief.
• The fact that Venus and Earth are so similar in size and composition but so different in surface conditions suggests that Venus could teach us important lessons.
• In particular, Venus’s greenhouse effect is caused by carbon dioxide, the same gas that is primarily responsible for global warming on Earth. Perhaps further study of Venus may help us better understand and solve some of the problems we face here at home

Question 16

Planet Overview:

Earth

Answer 16

• The only planet in our solar system with oxygen to breathe, ozone to shield the surface from deadly solar ultraviolet radiation, and abundant surface water to nurture life.
• Almost all other moons are much smaller relative to the planets they orbit.

Question 17

Planet Overview:

Mars

Answer 17

• The last of the four inner planets of our solar system
• Has two tiny moons, Phobos and Deimos, which may once have been asteroids that were captured into martian orbit early in the solar system’s history.
• The air pressure is far less than that on top of Mount Everest, the temperature is usually well below freezing, the trace amounts of oxygen would not be nearly enough to breathe, and the lack of atmospheric ozone would leave you exposed to deadly ultraviolet radiation from the Sun

Question 18

Planet Overview:

Jupiter - differences:

Answer 18

Jupiter is so different from the planets of the inner solar system that we must adopt an entirely new mental image of the term planet:
* Its mass is more than 300 times that of Earth, and its volume is more than 1000 times that of Earth.
* Its most famous feature—a long-lived storm called the Great Red Spot—is itself large enough to swallow two or three Earths
* Like the Sun, Jupiter is made primarily of hydrogen and helium and has no solid surface
* If we plunged deep into Jupiter, the increasing gas pressure would crush us long before we reached its core.

Question 19

Planet Overview:

Jupiter - reigns over dozens of moons and a thin set of rings

Answer 19

• Most of the moons are very small, but four are large enough that we’d call them planets or dwarf planets if they orbited the Sun independently.
• These four moons—Io, Europa, Ganymede, and Callisto—are often called the Galilean moons (because Galileo discovered them)

1. Io is the most volcanically active world in the solar system
2. Europa has an icy crust that may hide a subsurface ocean of liquid water, making it a promising place to search for life
3. Ganymede and Callisto may also have subsurface oceans, and their surfaces have many features that remain mysterious.

Question 20

Saturn

Question 21

ADD MORE ABOUT PLANETS

Question 22

What features of our solar system provide clues to how it formed?

Answer 22

1. Patterns of motion among large bodies
2. Two major types of planets
3. Asteroids and comets
4. Exceptions to the rules

Question 23

What features of our solar system provide clues to how it formed?

Patterns of motion among large bodies.

Answer 23

The Sun, planets, and large moons generally orbit and rotate in a very organized way. Patterns, i.e…
* All planetary orbits are nearly circular and lie nearly in the same plane.
* All planets orbit the Sun in the same direction: counterclockwise as viewed from high above Earth’s North Pole.
* Most planets rotate in the same direction in which they orbit, with fairly small axis tilts. The Sun also rotates in this direction.
* Most of the solar system’s large moons exhibit similar properties in their orbits around their planets, such as orbiting in their planet’s equatorial plane in the same direction as the planet rotates.

Question 24

What features of our solar system provide clues to how it formed?

Two major types of planets.

Answer 24

The planets divide clearly into two major groups: the small, rocky planets that are close together and close to the Sun, and the large, gas-rich planets that are farther apart and farther from the Sun.

Question 25

What features of our solar system provide clues to how it formed?

Asteroids and Comets

Answer 25

Between and beyond the planets, vast numbers of asteroids and comets orbit the Sun; some are large enough to qualify as dwarf planets. The locations, orbits, and compositions of these asteroids and comets follow distinct patterns.

Question 26

What features of our solar system provide clues to how it formed?

Exceptions to the rules.

Answer 26

The generally orderly solar system also has some notable exceptions. For example, among the inner planets only Earth has a large moon, and Uranus is tipped on its side. A successful theory must make allowances for such exceptions even as it explains the general rules.