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 Appears every 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 17 th meteors are called the Leonids because their radiant is in the constellation Leo.