Transcript Linking Asteroids and Meteorites through Reflectance Spectroscopy

Survey of the Universe
Tom Burbine
[email protected]
Moon, Planets, and Stars
• All celestial objects appear to rise in the east and
set in the west
Moon
• Besides the Sun, the Moon is the brightest object in
the sky
• The Moon reflects light from the Sun
• Light areas are called highlands
• Dark areas are called maria
(huge impact basins filled with lava)
http://sos.noaa.gov/datasets/solar_system/moon.html
Cycle
• The Moon’s changes in the sky follow a 29.5 day
cycle
• This is why each month has approximately 30
days
Phases
of the
Moon29.5
day
cycle
http://en.wikipedia.org/wiki/File:Lunar-Phase-Diagram.png
Color of lunar eclipse
• The Moon does not completely disappear because of the
refraction of sunlight by the Earth’s atmosphere
• If the Earth had no atmosphere, the Moon would be
completely dark during an eclipse.
• The red color arises because sunlight reaching the Moon
must pass through the Earth’s atmosphere, where it is
scattered.
• Shorter wavelengths are more likely to be scattered by the
small particles. By the time the light has passed through
the atmosphere, the longer wavelengths dominate. This
resulting light reflected from the Moon we perceive as red.
Solar eclipse
http://en.wikipedia.org/wiki/Image:Solar_eclips_1999_4_NR.jpg
• Solar eclipses occur approximately every 18 months
• However, they recur (on average) at any given place only
once every 370 years
• Moon's umbra moves eastward at over 1,700 km/hr
• Every year, there are at least two lunar eclipses.
• Can be viewed anywhere on the night side of the Earth
http://home.cogeco.ca/~astrosarnia/Photos/Lunar%20eclipse%20binocular.jpg
http://www.explorelearning.com/index.cfm?method=cresource.dspexpguide&resourceid=556
Eclipses
Moon is tilted at an angle of 5 degrees to Earth’s orbit
Solar eclipse of July 22, 2009
• Lasted a maximum of 6 minutes and 39 seconds
off the coast of Southeast Asia
http://upload.wikimedia.org/wikipedia/commons/f/f2/Solar_eclipse_animate_%282009-Jul-22%29.gif
http://en.wikipedia.org/wiki/File:Solar_eclipse_22_July_2009_taken_by_Lutfar_Rahman_Nirjhar_from_Bangladesh.jpg
Solar eclipse of July 11, 2010
• Occurred over the Southern Pacific Ocean
• Very remote
• Seen over French Polynesia,
the Cook Islands, and Easter Island
Models
• When you have a model of how something works,
you should be able to predict what will happen
• If observations do not fit the model, either the
observations or the model is wrong
• The ancient astronomers wanted to predict the
positions of planets in the sky
What did the ancients think
• That the Earth was the center of the universe
(geocentric model)
• That the celestial sphere was rotating around the
Earth
• However, there was two observations that caused
problems with this idea
– Apparent retrograde motion
– Inability to detect stellar parallax
Greek model
Motion of planets
• Planets always appear to rise in the east and set in
the west
• But planets usually move from west to east past
the stars
• The exception is retrograde motion
Figure 2.6
Figure 2.7
Apparent Retrograde Motion = “backward” motion
Ptolemy’s (100-170 AD)
Model of the Universe
epicycle
Occam’s Razor
• The principle that generally recommends
selecting the hypothesis that makes the fewest
new assumptions
Retrograde Motion
Any Questions?