2 Terms to Know…AsteroidCometKuiper BeltOort cloudMeteormeteoroid
3 Asteroids: large rock fragments that orbit the sun in elliptical orbits. Largest known asteroid is Ceres (1,000 km diam.)…also considered a dwarf planet b/c its gravity has caused it to be round.
4 Asteroid belt is located b/t Mars and Jupiter and contains most asteroids. Three types based on compositionCarbon (these asteroids are dark)Silicate (like Earth rocks)Fe, Ni (rare, shiny-metallic surface)Near-Earth Asteroids: very small percentage…asteroid detection programs monitor their movements.
5 Comets: ice, rock, dust, have tails—highly elliptical orbits around sun. Halley’s Comet-passes Earth every 76 yrs (next = 2061).Also famous: Hale-Bopp (shown below, 1997), McNaught (2007)
6 Parts of a comet:HeadCore (aka nucleus): rock, metals, iceComa: cloud of gas/dust2 TailsIon tail: Solar wind pushes gas away from the comet’s head so italways points away from the sun no matter which direction the comet is going.Dust tail: curves behind the comet
8 Where do comets come from? Some from Kuiper Belt (ring of icy bodies, including some dwarf planets, beyond Neptune’s orbit)Most from Oort Cloud (spherical cloud of dust/ice) Could reach as far back as halfway to a near star.
9 Some comets can have orbits up to a few million years Some comets can have orbits up to a few million years! Those >200 years are called long-period comets.Short period comet: <200 years to orbit sunLong period comet: > 200 years to orbit sunMeteoroids: small bits of rock/metalSmall meteoroids: detached comet piecesLarge meteoroids: result of colliding asteroids.
10 Meteors: shooting stars or fireballs (bright b/c friction of entering our atmosphere) Meteor shower: occur at the same time each year with the orbits of comets (comet leftovers).
11 Meteorites: meteor leftovers that made it to Earth’s surface Stony (most are stony)…carbon basedIron…(easier to find b/c metallic)Stony-iron (rarest)