comets & asteroids - monadnock regional high school · 2018-08-18 · comets • definition:...
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Comets & Asteroids
Comets • Definition: • Dirty snowball (rocks & ice)
• Origin: • Theory #1: During spherical nebular phase, ice
chunks formed in outer part of cloud. • These became comets in Oort cloud (outside solar
system)
• Theory #2: Some formed later from plantesimals in outer solar system, now in Kuiper Belt
Wild 2 Comet Stardust NASA mission
Evidence for Comets • Comets can have a short or
long period • Short: < 200 yrs • Long: 1 – 30 million years
• Comets can have orbit in the plane of the planets or not. • Composition: Water ice, CO2,
ammonia, methane, rock
Which type of comet are in the Oort cloud? Long or short period?
Parts of a Comet • Comets glow only as they
near the sun (become warm enough to reflect light – they’re too cold to luminesce otherwise)
• Nucleus: solid part, a few km across • Coma: luminous ball
around nucleus • Tail: dust trail of particles
breaking off comet – points away from the sun
Parts of a Comet
Tails of Comets • Comets have 2 tails • Dust Tail • Ion Tail • Range in size up to 1 AU!
• Tails always point away from the Sun, due to solar wind
Do Comets Melt? • Estimates are that
comets lose ~0.1% of initial mass each trip around the Sun.
• Particles from comet can continue to orbit even after comet disintegrates
(“Meteor” Showers)
Asteroids • Asteroid belt between Mars and Jupiter
was discovered in 1800, when Ceres was first thought to be a planet. • After other similar objects in same orbit were
discovered, it was reclassified.
• Asteroids have similar composition to rocky planets • Origin:
• Planet that never formed • Planet that broke apart
Asteroids vs. Meteoroids • Biggest difference is size! • Usually > 300 m ! asteroid
• Meteor’s name depends on where it is: • Meteoroid is in space • Meteor is falling through Earth’s atmosphere • Meteorite is on the ground.
Asteroid “Ida” and her moon
Asteroids vs. Meteoroids
2018 Meteor Shower Calendar • January 1st-5th – Quadrantids (peak 1/3)
• April 22nd-23rd – Lyrids • May 6th-7th – Eta Aquarids • July 28th-29th – Delta Aquarids • August 12th-13th – Perseids
• October 8th – Draconids • October 21st-22nd – Orionids • November 5th-6th – Taurids • November 17th-18th – Leonids • December 13th-14th – Geminids • December 21st-22nd - Ursids