Transcript class08

ASTR100 (Spring 2006)
Introduction to Astronomy
Collecting Light with Telescopes
Prof. D.C. Richardson
Sections 0101-0106
Why do we put telescopes into
space?
It is NOT because they are closer to the stars!…
Observing problems due to
Earth’s atmosphere
1. Light pollution.
2. Turbulence causes twinkling  blurs
images.
Star viewed with
ground-based
telescope.
View from Hubble
Space Telescope.
3. Atmosphere absorbs most of EM
spectrum, including all UV and X-ray,
most infrared.
Telescopes in space solve all
three problems
 Location/technology can help overcome
light pollution and turbulence.
 But nothing short of going to space can
solve the problem of atmospheric
absorption of light.
Chandra X-ray
Observatory
How is technology revolutionizing astronomy?
Adaptive optics
• Rapid changes in mirror shape compensate
for atmospheric turbulence.
Without adaptive optics
With adaptive optics
Adaptive Optics: Neptune
Without
With
Interferometry
• Allows two or more small telescopes to work together
to obtain the angular resolution of a larger telescope.
Very Large Array (VLA), New Mexico
The Moon would be a great spot for an observatory
(but at what price?)…
ASTR100 (Spring 2008)
Introduction to Astronomy
A Brief Tour of the Solar System
Prof. D.C. Richardson
Sections 0101-0106
What does the solar system look
like?
 The solar system exhibits clear patterns of
composition and motion.
 These patterns are far more interesting than
numbers, names, and other trivia!
Planets are
very tiny
compared to
distances
between
them.
Sun
• Over 99.9% of solar system’s mass.
• Made mostly of H/He gas (plasma).
• Converts 4 million tons of mass into energy per second.
Mercury
• Made of metal and rock; large iron core.
• Desolate, cratered; long, tall, steep cliffs.
• Very hot and very cold: 425°C (day), –170°C (night).
Venus
.
• Nearly identical in size to Earth; surface hidden by clouds.
• Hellish conditions due to an extreme greenhouse effect.
• Even hotter than Mercury: 470°C, both day and night.
Venus in Radar
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Earth
Earth & Moon
to scale
• An oasis of life.
• The only surface liquid water in the solar system.
• A surprisingly large moon.
Mars
• Looks almost Earth-like, but
don’t go without a spacesuit!
• Giant volcanoes, a huge
canyon, polar caps, more…
• Water flowed in the distant
past; could there have been life?
Rovers on Mars!
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YUV420 codec decompressor
are needed to see this picture.
Jupiter
• Much farther
from Sun than
inner planets.
• Mostly H/He;
no solid surface.
• 300 times
more massive
than Earth!
• Many moons,
rings…
Moons can be
as interesting
as planets
themselves,
especially
Jupiter’s four
Galilean moons.
•
•
•
•
Io (shown here): active volcanoes all over.
Europa: possible subsurface ocean.
Ganymede: largest moon in solar system.
Callisto: a large, cratered “ice ball”.
Earth!
Saturn
•
•
•
•
Giant and gaseous like Jupiter.
Spectacular rings.
Many moons, including cloudy Titan.
Cassini spacecraft currently studying it.
Saturn
Rings are
NOT solid;
they are
made of
countless
small chunks
of ice and
rock, each
orbiting like a
tiny moon.
Artist’s conception
Saturn
Cassini probe
arrived July
2004.
(Launched in
1997).
Uranus
• Smaller than
Jupiter/Saturn; much
larger than Earth.
• Made of H/He gas
and hydrogen
compounds (H2O,
NH3, CH4).
• Extreme axis tilt.
• Moons and rings.
Neptune
• Similar to
Uranus (except
for axis tilt).
• Many moons,
including Triton.
Pluto and Eris
• Much smaller than other planets.
• Icy, comet-like composition.
• Pluto’s moon Charon is similar in size to Pluto.
Comets & Asteroids
• Leftovers from
planet formation.
• Tiny worlds of ice
and/or rock.
• Some even have
moons!
Comet P/Tempel 1
Asteroid 25143 Itokawa
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Quiz!
 Which body in the solar system has
the most mass:
A.
B.
C.
D.
Earth
Jupiter
The Sun
The Moon