MINOR PLANETS, COMETS, AND METEORS

MINOR PLANETS

A.K.A. – Asteroids Very small “star-like” Visible through a telescope Most are binary (2 orbiting each other) Most orbit between Mars and Jupiter

MINOR PLANETS

There are at least 100,000 Named by year discovered

and 2-letter suffix (AA-ZZ) showing month and sequence

Trojan Asteroids are in front of and behind Jupiter in its orbit, and they are as far from the sun as they are from Jupiter.

MINOR PLANETS

Have “families” that are similar in composition or travel together Near-earth families include: Apollo, Aten,

Amor

Danger of Asteroid Strike? Highly Unlikely God is in control

COMETS

Visible without a telescope Discovery:

1. A light in the atmosphere? 2. Move in straight lines (rather than ellipses)? 3. Edmund Halley treated comets as celestial objects

He calculated the orbits of several comets and found 3 of them to have nearly the same orbit.

The time between each was also similar, so he predicted they were the same comet.

“Halley’s comet” has appeared on schedule four times since his death. Next sighting should be in 2061.

Appears every 75-76 years…

COMETS

Structure: Coma = an envelope of ice particles surrounding

the nucleus Ices, dust, gas

Low temperature – reflects sunlight (difficult to see)

High temperature – fluoresces (bright)

Nucleus = contains most of a comet’s material Ices, rocks, dust

Tails Type I = straight, forms quickly, made of gas

Type II = curved, forms slowly, made of dust

COMETS

Comets that keep returning have elliptical orbits and are called “periodic” comets.

Solar energy drives the material of the comet’s tail into space where it is lost from the comet.

Can be torn apart by gravitational pull of other planets and the sun

When they strike earth’s atmosphere, they vaporize.

Can only last hundreds (maybe thousands) of years

METEORS

“Shooting Stars” Visible to unaided eye Only last briefly The space fragment glows as earth pulls it

downward and friction heats it. Made of silicate, iron, and nickel

METEORS

Meteoroid = when a particle of rock or dust orbits the sun

Meteor = when a meteoroid begins to glow as it enters earth’s atmosphere

Meteorites = meteoroids large enough to become fireballs that survive the fall through earth’s atmosphere and reach the ground

METEORS

Most are sporadic fall from random directions

at any time

Meteor showers occur when concentrations of meteoroids in distinct orbits cross the earth’s orbit at several points

Radiant = a point in the sky from which meteors appear to radiate

Example: November 17th meteors are called the Leonids because their radiant is in the constellation Leo.