Fate of planetesimals
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Fate of Planetesimals. Ejection from Sol. Sys. Collision with planets Capture as satellites, or into resonant orbits (e.g., the Trojan asteroids) Fragmentation Preservation to today (however, not necessarily in “ pristine ” condition) comets asteroids meteors. Comets.

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Fate of Planetesimals

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Fate of planetesimals

Fate of Planetesimals

  • Ejection from Sol. Sys.

  • Collision with planets

  • Capture as satellites, or into resonant orbits (e.g., the Trojan asteroids)

  • Fragmentation

  • Preservation to today (however, not necessarily in “pristine” condition)

    • comets

    • asteroids

    • meteors


Comets

Comets

  • “comet” from “kome” (Gr.), meaning “hair” being descriptive of comet tails

  • Comets have been seen since ancient times, often considered bad omens

  • 1577 – Brahe deduced that comets are farther than the Moon from lack of parallax (as Earth rotates)

  • 1704 – Edmond Halley uses Newton’s gravity to discover that comets move on long elliptical orbits:

    Comets seen in 146, 1531, 1607, and 1682 are the same [also records for 66 and 451], with Porb= 75 yrs – Halley predicted its return in 1758

    Halley’s comet!


Comet ikeya zhang

Comet Ikeya Zhang


Nature of comets

Nature of Comets

WHAT“dirty snowballs”

WHERE

  • The Oort cloud – named after discoverer Jan Oort (Dutch), a swarm of “dormant” comets at ~50,000 AU

  • Long periods (using P2=a3, P ~ 105-107 yrs)

  • Since they travel at less than vesc from the solar system as theyapproach, comets are thought to be part of S.S., in contrast to interstellar wanderers


The oort cloud

The Oort Cloud


Comet hyakutake

Comet Hyakutake


Comet components

Comet Components

  • Nucleus: the “snowball”, of a few km in diam.

  • Coma: halo of gases enveloping the nucleus, about 106 km in diam.

  • Tails: can extend to over 1AU; directed away from Sun

    • Plasma tail – driven back by ionized solar wind

    • Dust tail – repelled by sunlight, like mini-solar sails


Anatomy of a comet

Anatomy of a Comet


Comet holmes 2007

Comet Holmes (2007)


Tail development

Tail Development


Share question

Long-period comets have orbits

a) the same as the orbits of short-period comets

b) that are circular

c) always in the ecliptic

d) randomly oriented with respect to the ecliptic

e) of low eccentricity

Share Question


Comet close up

Comet Close-up

  • Giotto, a European probe, obtained 1st close-up images of Halley’s comet during its 1986 passage

    • Peanut shaped

      15 x 7 x 10 km

    • Jets of gas and dust


Halley s comet

Halley’s Comet


Comet hale bopp

Comet Hale-Bopp


Chunks of shoemaker levy 9

Chunks of Shoemaker-Levy 9


Comet impacts at jupiter

Comet Impacts at Jupiter


Stardust mission

Stardust Mission


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