The Solar System

Question 1

Name and categorise the 8 planets.

Answer 1

Rocky/Terrestrial
Mercury / Venus / Earth / Mars
Gas Giants
Jupiter / Saturn / Uranus /Neptune

Question 2

What is the definition of a planet?

Answer 2

A planet is a body that:

• Is in orbit around the Sun
• Is large enough to be Spherical
• Has cleared its orbit of other objects.

Question 3

Name 6 other types of body in our Solar System.

Answer 3

• Asteroids (Vesta / Pallas)
• Comets
• Centaurs (Half comet, Half Asteroid)
  Orbit between Jupiter and Neptune
• Moons/satellites (160 known)
• Dwarf Planets (Pluto, Ceres, Eris)
• TNOs (Trans Neptunian Object)
  Objects orbiting beyond Neptune

Question 4

Name 2 decisions of the IAU (International Astronomical Union) taken in 2006.

Answer 4

• Ceres promoted from Asteroid to dwarf planet

- Pluto demoted from planet to dwarf planet.

Question 5

What is 1 AU (Astronomical Unit) ?

Answer 5

Unit of Measurement
Based on distance between Earth and Sun
150 million km

Question 6

Describe Mercury.

Answer 6

• It is the closest to the sun
• Fastest orbital period. Smallest planet
• Heavily cratered
• Highlands and lava filled basins.

Question 7

What is odd about Venus?

Answer 7

It spins backwards.

Retrograde Rotation

Question 8

Describe Venus.

Answer 8

It is a similar size to Earth
Clouds of Sulphuric Acid
Atmosphere of mostly Carbon Dioxide
Runaway Greenhouse Effect
Temp 470 degrees C
Pressure
90 x Earth’s

Question 9

Describe Mars.

Answer 9

Iron rich rocks
Red planet
450km long water carved canyons
Mariner Valley
Highest volcano in solar system
Olympus Mons

Question 10

What is the Great red spot on Jupiter?

Answer 10

It is an anticyclone weather system greater in size than Earth.

Question 11

How many times bigger than Earth is Jupiter?

Answer 11

11 (approx)

Question 12

Describe Jupiter’s equatorial bulge and explain why it has one.

Answer 12

• Dynamic wind system splits atmosphere into belts and zones

- Bulge due to extremely fast rotation (once in only 10hrs)

Question 13

How long is a Venus day?

Answer 13

243 Earth days.

Question 14

Name some similarities between Uranus and Neptune.

Answer 14

-Similar Size
-They are both cold Gas Giants.
(Hydrogen / Helium / Methane / Ammonia)

Question 15

Describe some similarities and differences between Jupiter and Saturn.

Answer 15

-Both have ring systems
(Jupiter’s not as reflective as Saturn’s)
-Both are gas giants
-Similar rotational periods
-Saturn has less visible structure to its atmosphere
(unlike Jupiter which has Great Red Spot, red/brown belts and yellow/white zones.)

Question 16

Name some differences between Uranus and Neptune?

Answer 16

• Uranus is almost featureless.
• Uranus spins on its side.
• Neptune has a Great Dark Spot.
• Neptune has clouds of frozen methane.

Question 17

Name 5 problems Astronauts could face if venturing beyond the Moon.

Answer 17

-Time
-Space adaptation syndrome
(No up and no down / Disorientation / Headaches / Vomiting / Poor concentration)
-Physiological problems, prolonged zero gravity causes: (Muscle wasting. Brittle bones, Reduced red cell count)
-Psychological problems: Confined spaces with the same group of people.
-Communication delays
-Radiation Risk

Question 18

Name some advantages of robotic planetary exploration.

Answer 18

Less expense
No loss of life
Safer

Question 19

Name Mars’ two small moons.

Answer 19

Deimos

Phobos

Question 20

Why do Astronomers believe that Deimos and Phobos are captured Asteroids?

Answer 20

Heavily cratered.
Irregular in shape.
Densities half that of Mars.
Compositions similar to Asteroids.

Question 21

Name 3 moons of Neptune.

Answer 21

-Triton
-Dark Proteus (Largest Irregular moon of Solar System. Orbits in the plane of Neptune’s equator.
Suggesting it was formed at the same time as Neptune.)
-Nereid. (Highly eccentric orbit, 1 orbit is 1 Earth year. Probably captured Kuiper Belt object.)

Question 22

Why do astronomers believe Triton is also a captured body?

Answer 22

• Revolves around Neptune in the opposite direction to Neptune’s rotation.
• Highly inclined orbit.
• It is thought that Triton’s capture is the result of a collision with Neptune or one of it’s moons.

Question 23

Name 4 planets that have ring systems.

Answer 23

Saturn.
Jupiter.
Neptune.
Uranus.

Question 24

Why aren’t Jupiter’s rings visible like Saturn’s rings?

Answer 24

Saturn’s rings are made out of highly reflective ice particles.
Jupiter’s rings are made out of dark dust.

Question 25

How thin are ring systems?

Answer 25

All are < 1.5 km thick.

Question 26

What are the gaps in Saturn’s rings called.

Answer 26

The Cassini Division.

Question 27

Which planets have incomplete rings (arcs)?

Answer 27

Neptune. | Uranus.

Question 28

Give 4 theories on the origin of rings.

Answer 28

- Debris left over from planet formation. - Large impacts between moons. - Moons torn apart through tidal gravitational forces. - Meteors striking moons creating debris.

Question 29

Are the orbits of planets circular?

Answer 29

No they are elliptical.

Question 30

What is the plain on which the planet’s orbit called?

Answer 30

The ecliptic.

Question 31

What is the Zodiacal band?

Answer 31

Because all the planets orbit on the ecliptic, they appear to move through a narrow region of the sky called the Zodiacal band.

Question 32

What are the Inferior Planets?

Answer 32

Mercury and Venus | Also known as the Inner Planets

Question 33

What are the Superior Planets?

Answer 33

Mars, Jupiter, Saturn, Uranus, Neptune.

Question 34

Where do the Inferior Planets appear in the sky?

Answer 34

Near the sun. | Best observed at sunset or sunrise

Question 35

At what time in their orbit is it best for us to see Mercury and Venus?

Answer 35

At their GEE (Greatest Eastern Elongation) or GWE (Greatest Western Elongation).

Question 36

What is the GEE and GWE?

Answer 36

At the GEE and GWE the angle between the lines planet-Earth and planet-Sun is 90 degrees.

Question 37

At GEE, when will the inferior planet be visible?

Answer 37

Shortly After Sunset.

Question 38

At GWE when would the inferior planet be visible?

Answer 38

Shortly before Sunrise.

Question 39

What is an inferior conjunction?

Answer 39

When the angle of elongation is 0. Planet passes between Sun and Earth. May undergo a transit. (May cross over the solar disc)

Question 40

What is a superior conjunction?

Answer 40

When the angle of elongation is 0. When the planet passes behind the sun. May undergo an occultation (Disappears behind sun.)

Question 41

When are the superior planets most favourably placed for observation and why?

Answer 41

At opposition, because: - Brighter (Fully illuminated by sun throughout night) - Better resolution (Closest to Earth)

Question 42

Explain Retrograde Motion.

Answer 42

-Direct motion of planet seems to stop and move backwards in a “loop the loop” pattern before stopping again and resuming its original direction. -This is because Planets orbit the sun at different speeds (Angular, Actual) - We therefore see planets from different viewpoints (as we also orbit the Sun). Sometimes overtaking the inner planets Sometimes undertaking the outer planets.