Asteroids

Main Asteroid Belt
Asteroids are rocky minor planets that orbit the Sun, distinguished from comets by their lack of a tail (comet tails are composed of ice and frozen gases that melt when near the Sun, producing the tail we see, asteroids lack these).

The belt was formed approximately 4.6 billion years ago, along with the Sun and other planets.

• It's located between Mars and Jupiter.



• It hasn't condensed into a single planet because of the competing gravitational pull of Jupiter and the Sun.



• Asteroids inside the belt range in size from 1 km across to 959 km (dwarf planet Ceres).\



• There are ~440,000 documented asteroids within the belt, though the belt contains millions of others.



• The total mass of asteroids in the belt is estimated to be less than the Earth's Moon.



• 92.8% of asteroids within the belt are composed of stony materials (olivine, pyroxene, etc), and 5.7% are mainly iron and nickel.



• The first named dwarf planet, Ceres, was discovered by Giuseppe Piazzi in 1801.

Ida 243:
Ida is an asteroid in the Main Asteroid Belt, discovered by the Austrian astronomer Johann Palisa in 1884. It is the first asteroid to be discovered to have a natural satellite (Dactyl), and the second asteroid to be observed by a satellite.

• 
  
  Ida and its satellite, Dactyl
  
  Ida was named for a nymph who tended the god Jupiter (Greek Zeus) when he was young, it's also the name of a mountain on Crete where Jupiter was raised.



• Ida is a member of the Koronis family of asteroids, meaning it originated from a single large asteroid impact.
  


• Ida has a mass of 1334 kg.



• It's 428,000,000 km from the Sun.



• One day is 4 hours and 39 minutes.



• Its average diameter is 31.4 km.


• Ida has a temperature of -73 C.


• Ida is a chrondrite asteroid, meaning that it's made mainly of dust from the early Solar System, composed of olivine, pyroxene, etc.



• Ida is covered with 50-100 m of regolith (pulverized rock from other asteroid impacts) over all of its surface.


• Observed by the Galileo spacecraft in August 28, 1993, the second asteroid to have been observed at such a close distance (only 10,760 km away from Ida and 10,870 km from Dactyl)




• Dactyl is named for the Dactyli, which were mythical residents of Mount Ida.



• Dactyl orbits Ida at 90 km/h, has a size of 2.688 km3, and has the same temperature as Ida.

Vesta:

Vesta is a 'minor planet' in the main belt, it has a c0mposition similar to Mars or Earth, and has differentiated, or undergone the process where dense materials sink to the core and lighter materials rise to the top.

• Vesta was discovered by Heinrich Wilhelm Olbers on March 29h, 1807.



• It is composed of 86% rocky materials (olivine, pyroxene, feldspar) and 14% iron.



• Has a diameter or 525 km.



• Its day is 5 hours and 20.5 minutes.



• Vesta has a mass of 78,800,000 kg, which is 279 times smaller than the Earth's Moon.

Near Vesta's South Pole, there is a 20-30 km wide and 20-30 km deep crater, which is the source of Howardite-Eucrite-Diogenite (HED) meteorites on Earth.

Vesta is visible to the naked eye from Earth.

Vesta's symbol is

99942 Apophis:

Apophis is one of the few asteroids that have been discovered on a collision course with Earth, and one of the even fewer that could cause total extinction on Earth.

Discovered on June 19th, 2004, at the Kitt Peak Observatory.

• It was then determined to have a 2.7% chance of impact with Earth in 2029.



• Apophis is 210-330 km in diameter.



• It was detected at 27 - 40 million km from the Earth.



• It was later determined that Apophis posed only a 1/45,000 chance of impact on April 13th, 2036.

Dawn Program:

The Dawn Program is dedicated to learning more about the origins of the Solar System and how planets and other objects were created. Dawn itself is a satellite that is exploring objects in the main asteroid belt, namely Vesta and Ceres. It has nearly arrived, and will begin its observations of Vesta on August 5-7th of this year.

Kuiper Belt:

The Oort Cloud and Kuiper Belt, w/ Relative Scale

The Kuiper Belt is a vast, disc-shaped region beyond the orbit of Neptune that produces short-period comets, or comets that take less than 200 years to orbit around the Sun.

• Contains hundreds of thousands of icy bodies larger than 100 km across, and approximately a trillion comets.



• Extends from 30-55 AU from the Sun.

The Oort Cloud:

The Oort Cloud is a region of space proposed by Jan Oort in 1950, it is supposedly a vast outer shell of icy bodies and comets, and marks the edge of the Solar System and the Sun's gravitational influence.

• Contains 100,000,000,000 to 2,000,000,000,000 icy bodies.



• Extends 5,000 to 100,000 AU from the Sun.



• The Oort Cloud produces long-period comets, 0r comets that take more than 200 years to orbit. Gravitational interaction with the Milky Way dislodges these into the inner Solar System.

All note sheets and the Moodle instructions can be found here.