28 comets asteroids

download report

Transcript 28 comets asteroids

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
Amount of parent element
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
Tails point away from the Sun
(like a wind sock!).
Wikipedia
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 by
stellar 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 a
YUV420 codec decompressor
are needed to see this picture.
Approach movie from the
impact probe itself!
QuickTime™ and a
Sorenson Video 3 decompressor
are needed to see this picture.
Approach movie
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)
IAU definition 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.!