Post on 20-Dec-2015
transcript
Agenda
Short practice test Asteroids Comets Pluto Get a review sheet!
Thursday is a review, but is not “optional.”
Phobos
Asteroids
Some are differentiated Range in size: less than 1 km to
almost 1000 km Near Earth objects are being tracked
by NASA
Meteors fall to Earth sometimes
They are then called Meteorites.
4.55 billion yrs old Similar to moon oldest Earth rocks helioseismic age of Sun
Can contain amino acids and water
2 kinds: Stony meteorites and...
...Iron meteorites
Very dense Iron and nickel
Get out your planner, and schedule PERSEID METEOR SHOWER for the night of August 12. That would be a good night to invite some friends over, put out the lawn chairs, and spend a relaxed evening in the back yard.
How are rocks dated?
Radiometric dating! Some elements naturally decay into
lighter elements Half life – when half of the original
element is left
Comets
Made of ice and solids Small solid nucleus Much larger head, or
coma Large, very elliptical
orbits Meteor showers are
caused by debris in cometary orbits!
Comet Halley, 1985 (AAT)
Halley’s period is 75 years.
How much of the time can we see it with unaided eyes?
A. 37 years, or about half its period.
B. 65 years (that is, most of the time!)
C. About a year or less.
D. Not enough information.Reason: Kepler’s laws. Comets spend most of their time in the outer solar system.
Approach movie from the impact probe itself!
Approach movie
QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.
IAUdefinition of a planet
Which of the following is NOT part of the official definition of a planet?
A. In orbit around the Sun
B. Has an atmosphere
C. Massive enough to be round
D. Has cleared the neighborhood around its orbit
Summary
Asteroids Live in asteroid belt Made of terrestrial material
Comets Live in Kuiper belt and Oort cloud
Pluto is a Kuiper belt object too!
Very elliptical orbits Made of ice, dirt 3 parts: coma, nucleus, tails