ASTR 1010 – Homework Assignment 7 – Spring 2009

Question 1 - #3. You have 4 small, dense planets, known as the terrestrial planets, very close to the Sun. Then, at 2-4 AU you have a zone of small, rocky/metallic debris known as the Asteroid Belt. Beyond the Asteroid Belt are 4 giant, gaseous and icy worlds (Jupiter and Saturn are gaseous, Uranus and Neptune are mostly icy). These objects differ from the terrestrial planets in that they are much larger, have lower densities, have lots of satellites, and all have ring systems (only Saturn’s looks cool). Beyond Neptune lie the Kuiper Belt and the Oort Cloud, both regions of icy debris, the first planar and fairly close to the Sun (< 100 AU), the latter spherical and extending nearly halfway to the nearest star (i.e., almost 100,000 AU).

Question 2 - #4. Sun: Its mass and energy production.

Mercury: Its large iron core; the 2/3 ratio between rotation and orbital periods.

Venus: Its incredibly thick atmosphere and ensuing greenhouse effect; its surface features.

Earth: Our Moon; Deborah Harry.

Mars: Did it once have water/life? Its surface features (volcanoes, canyons).

Jupiter: The Galilean satellites; its magnetic field.

Saturn: Dude, the rings. Its moon, Titan.

Uranus: Its gorgeous blue color; its ring system.

Neptune: Features in its deep, blue atmosphere; its moon Triton.

Pluto: Its role in the Kuiper Belt; its moon Charon.

Question 3. - #5. See p. 224, Feature 1.

Question 4. - #6. Terrestrial planets: Mercury, Venus, Earth, Mars. Relatively small objects. Rocky/metallic bodies (thus, high-density), no satellite system that formed with the planet (Earth’s Moon results from a collision, martian moons were captured asteroids). No ring systems.

Jovian planets: Big. Ring systems. Lots of satellites. Gaseous atmospheres. Low-density. Lots of space between their orbits.

Question 5. - #9. Asteroids are debris left over from the formation of the Solar System. They are primarily located in two places: The Asteroid Belt (2-4 AU), and the Kuiper Belt (30-100? AU). Asteroid Belt objects are rocky & metallic, Kuiper Belt objects are icy.

Question 6. - #10. Comets are basically asteroids from either the Kuiper Belt or the Oort Cloud that pass near the Sun. Short-period comets come from the Kuiper Belt and are on elliptical orbits. They show the traditional cometary features as they near the Sun. Single apparition comets approach the Sun on hyperbolic orbits (and are thus one-time visitors unless a gravitational encounter with one of the giant planets puts them on an elliptical orbit).

Question 7. - #11. The Kuiper Belt is a planar distribution of icy asteroids located between 30 and maybe 100 AU from the Sun. It is the repository of the short-period comets. The Oort cloud is also a repository of icy asteroids, but it is located much further out and extends perhaps half-way to the nearest star (i.e., about 100,000 AU, the nearest star is about 260,000 AU away). The objects in the Oort cloud have a spherical distribution and it is the region where the long-period and single-apparition comets come from.

Question 8. - #42. Jupiter is 11 times the size of the Earth. Because volume scales as the radius to the third power, then you could fit ~ 11³ ~1300 Earths inside Jupiter.

Question 9. - #44. Mass = 5.97 x 10²⁵ kg

Radius = 1.28 x 10⁴ km = 1.28 x 10⁷ m

Volume = 8.78 x 10²¹ m³

Density = 6.8 x 10³ kg/m³ = 6.8 gm/cm³

This would be the largest of the terrestrial-type planets.