Voyagers (1970s)Voyagers (1970s)

• 1800 lbs, dish >12 ft diameter

• data rates ~115,000 bits/sec (twice dial-up!)

• Radioisotope Power Generators

MoonsMoons

Io Europa

CallistoGanymede

(Covered in the video…)

Galileo Mission (1989-2003)Galileo Mission (1989-2003) First detection of First detection of

ammonia in the clouds ammonia in the clouds of Jupiterof Jupiter

Imaged impact by Imaged impact by comet Shoemaker-comet Shoemaker-Levy in 1994Levy in 1994

Found it likely that Found it likely that there is a 100-km there is a 100-km deep ocean under the deep ocean under the ice of Europaice of Europa

Studied thunderstormsStudied thunderstorms On the way, On the way,

discovered asteroid discovered asteroid Ida has a moonIda has a moon

SaturnSaturn

Now: In retrograde, rises in ENE at about 10pm and is 60 degrees up at dawn [Fall 2005]

RingsRings

• Within Roche Limit (3 body problem…)

• < 2km thick

• dust to boulders+

Cassini / Huygens (1997 - ?)Cassini / Huygens (1997 - ?)

Cassini still orbiting Cassini still orbiting Saturn, Saturn, HuygensHuygens probe probe landed on its moon, landed on its moon, TitanTitan, last January , last January

Many discoveries, nicely Many discoveries, nicely listed in this top-10 listlisted in this top-10 list

……Huygens probe will be dropped onto TitanHuygens probe will be dropped onto Titan

What will happen?What will happen?Science News Science News

Article, postedArticle, posted

UranusUranus

• In Aquarius, magnitude 5.7

““Rotisserie” spin during 84-yr orbitRotisserie” spin during 84-yr orbit

1985

Close to here now

MoonsMoons

NeptuneNeptune

8th magnitude, in Capricornus

Looks essentially stellarLooks essentially stellar

Neptune’s MoonsNeptune’s Moons

• Giant Triton orbits retrograde, spiraling toward Roche’s limit in 10 – 100 million years

• Nereid smaller with prograde but very eccentric orbit

PlutoPluto

• 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 CharonPluto and Charon

• One synchronous satellite, discovered in 1978

Two new moons found with HSTTwo new moons found with HST

New Horizons MissionNew 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: Farther out: ShortShort-period comets -period comets come from the Kuiper beltcome from the Kuiper belt

P<200 yearsP<200 years Extends from Extends from

Neptune’s orbit Neptune’s orbit out to about out to about 1000 AU1000 AU

ShortShort-period-period comets are KB comets are KB objects objects perturbed perturbed toward the sun toward the sun by the giant by the giant planets.planets.

Farther out: Oort CloudFarther out: Oort Cloud

In 1950 Jan Oort noticed In 1950 Jan Oort noticed that:that:

no comet has been no comet has been observed with an orbit observed with an orbit that indicates that it that indicates that it came from interstellar came from interstellar space, space,

there is a strong there is a strong tendency for tendency for apheliaaphelia of of long period comet orbits long period comet orbits to lie at a distance of to lie at a distance of about 50,000 AU, and about 50,000 AU, and

there is no preferential there is no preferential direction from which direction from which comets come. comets come.

Thus….Thus….

LongLong-period -period Comets perturbed in Comets perturbed in from Oort Cloudfrom Oort Cloud

Speaking of comets…