Agenda

Short practice test Asteroids Comets Pluto Get a review sheet!

Thursday is a review, but is not “optional.”

Phobos

Warm up exercise for final exam

Only answer questions 1-22

Include last and first name only

Solar system “minor bodies”

Asteroids

Comets

Asteroids

Asteroids

Some are differentiated Range in size: less than 1 km to

almost 1000 km Near Earth objects are being tracked

by NASA

Asteroids

http://apod.nasa.gov/apod/ap060328.html

Eros flyby

NEAR Shoemaker landing site on Eros (Feb 1, 2001)

Composition of Eros

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

Time

Am

ount

of

pare

nt e

lem

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Siberian mystery: Tunguska

1908 explosion 1000 times more

powerful than Hiroshima bomb

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)

Elliptical orbit, 2 tails

Wikipedia

Tails point away from the Sun (like a wind sock!).

Nucleus of Halley’s comet!

(10 km long)

Coma is larger than Mercury!

Nucleus is smaller than one pixel on this image!

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.

Ions pushed bystellar winds

Dust tail,often curved

Deep Impact July 4, 2005

Impact probe of Comet Tempel-1 to see what would happen!

Tempel-1 (time lapse)

Brightens on impact!

Bursts during approach

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Approach movie from the impact probe itself!

Approach movie

QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.

What did it teach us?

Website: deepimpact.umd.edu

Kuiper belt and Oort cloud

Pluto

“Kuiper belt” object Discovered 1930 by Clyde Tombaugh Frozen nitrogen & methane, –220˚C

Pluto is little.

Pluto’s moons

Charon Nix & Hydra

discovered mid-2005

Pluto

Demoted to “dwarf planet” (2006)

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

Pluto

Bye bye, Pluto!

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

Time to evaluate my teaching

Pass out review sheets I need a volunteer to collect them Return to the physics office (EPS 264)

after class. Back in 15 min.!

Leav

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