Asteroids Andrew Horne

What is an asteroid?

Apophis

Initial error ellipse Later, more accurate prediction Earth Latest, most accurate prediction

Near Earth Asteroids (NEAs)

Kirkwood Gaps

Trojan Asteroids

Occupy the same orbit as Jupiter Are found at Jupiter’s Lagrangian Points L 4 and L 5 Either lead or trail Jupiter by 60° Are also found in Mars and Neptune’s orbit Occupy the same orbit as Jupiter Are found at Jupiter’s Lagrangian Points L 4 and L 5 Either lead or trail Jupiter by 60° Are also found in Mars and Neptune’s orbit

The Lagrangian points are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects 60°

Trojan Asteroids Occupy the same orbit as Jupiter Are found at Jupiter’s Lagrangian Points L 4 and L 5 Either lead or trail Jupiter by 60° Are also found in Mars and Neptune’s orbit

Trojan Asteroids Occupy the same orbit as Jupiter Are found at Jupiter’s Lagrangian Points L 4 and L 5 Either lead or trail Jupiter by 60° Are also found in Mars and Neptune’s orbit

Hirayama Families o Are groups of minor planets that share similar orbital elements, such as semimajor axis, eccentricity, and orbital inclination. o Are thought to be fragments of past asteroid collisions. o Are usually named after the family’s biggest member

Exploring an Asteroid The first flyby was completed by the Galileo spacecraft.

NEAR-Shoemaker ( )

1150 m700 m 250 m NASA

Measurements Obtained The density of Eros is 2670 kg m -3. It has most likely been fractured. From gamma-ray spectroscopy, it appears Eros contains K, Th, U, Fe, O, Si, and Mg.

Classes of Asteroids S-type: – Reside in the inner part of the belt (2-3.5 AU) – Surfaces consist of silicates, stony surface – 17% of all asteroids are of this type ( 2 nd most abundant ) M-type: – Metal rich, dominated by iron and nickel – Appear slightly reddish – Third most common, behind S and C

Classes of Asteroids C-type: – Nearly 75% of Asteroids are C-type – Rich in carbonaceous material – Appear very dark, found throughout the belt P-type: – Rich in ancient organic compounds – Appear slightly reddish – Found near outer edge of belt

Classes of Asteroids D-type: – Much like P-type, but appear redder and are farther from the sun – Trojans are a good example – Some of Jupiters smaller moons exhibit spectra similar to D-type asteroids

Albedo Asteroid TypeAlbedo S-type M-type C-type P-type D-type The albedo of an object is a measure of how strongly it reflects light from light sources such as the Sun.

Is an asteroid going to hit the Earth?