Download Long-period

Voyagers (1970s)
• 1800 lbs, dish >12 ft diameter
• data rates ~115,000 bits/sec (twice dial-up!)
• Radioisotope Power Generators
Moons
(Covered in the video…)
Io
Ganymede
Europa
Callisto
Galileo Mission (1989-2003)
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First detection of
ammonia in the clouds
of Jupiter
Imaged impact by
comet ShoemakerLevy in 1994
Found it likely that
there is a 100-km deep
ocean under the ice of
Europa
Studied thunderstorms
On the way,
discovered asteroid
Ida has a moon
Saturn
Now: In retrograde, rises in
ENE at about 10pm and is 60
degrees up at dawn [Fall 2005]
Rings
• Within Roche Limit (3
body problem…)
• < 2km thick
• dust to boulders+
Cassini / Huygens (1997 - ?)
Cassini still orbiting
Saturn, Huygens probe
landed on its moon,
Titan, last January
Many discoveries, nicely
listed in this top-10 list
…Huygens probe will be dropped onto Titan
What will happen?
 Science News
Article, posted
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Uranus
• In Aquarius, magnitude 5.7
“Rotisserie” spin during 84-yr orbit
Close to here now
1985
Moons
Neptune
8th magnitude, in Capricornus
Looks essentially stellar
Neptune’s Moons
• Giant Triton orbits retrograde, spiraling toward
Roche’s limit in 10 – 100 million years
• Nereid smaller with prograde but very eccentric
orbit
Pluto
• Very faint (15th magnitude)
• discovered with 13-inch telescope using
at Lowell by Clyde Tombaugh, by
examining plates with a blink comparator
• Orbit within Neptune’s at times (’80-99)
Pluto and Charon
• One synchronous satellite,
discovered in 1978
Two new moons found with HST
New Horizons Mission
• Launch January, 2006
•Swing by Jupiter in 2007
•Pass by Pluto/Charon 2015, ASAP,
before atmosphere freezes out.
• Kuiper belt by 2026
Farther out: Short-period comets
come from the Kuiper belt
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P<200 years
Extends from
Neptune’s orbit
out to about
1000 AU
Short-period
comets are KB
objects
perturbed
toward the sun
by the giant
planets.
Farther out: Oort Cloud
In 1950 Jan Oort noticed
that:
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no comet has been
observed with an orbit
that indicates that it
came from interstellar
space,
there is a strong
tendency for aphelia of
long period comet orbits
to lie at a distance of
about 50,000 AU, and
there is no preferential
direction from which
comets come.
Thus….
Long-period Comets perturbed in
from Oort Cloud
Speaking of comets…