Everything Else in the Solar System

Asteroids

Planetoids that mainly lie in belt between Jupiter & Mars Ceres (∼ 900 km radius) larger than rest Total mass << Mercury
Paths of the
  • earth (green),
  • Mars (red square)
  • Jupiter (yellow)
  • twelve brightest asteroids

Various special groups, also gaps which are due to various tidal resonance positions (e.g. 1:2 with Jupiter). Trojans in 600 δ with sun & Jupiter (old solution of 3-body problem: Lagrangian points L4 and L5!)
Hilda asteroids in 2:3 resonance with Jupiter (∼ 7.8 yr period)

Most asteroid orbits lie in plane of solar system, a few are very tilted. Most lie between Mars and Jupiter, maybe more beyond Jupiter (Centaur asteroids). two Centaur Asteroids (outer Chiron and 1991DA). Orbits clearly imply that they were never part of a single object which exploded
Have now had close-up look at several asteroids. This is Gaspara
Ida and its moon, Dactyl.
Eros is a lump of rock
We can even watch it rotate
W have managed to land on Eros:
the fourth object (after the Moon, Mars and Venus) in the Universe! (but a bit too hard!)
Quaoar is (almost) the most distant known object in the solar system

Meteors:

These are the Leonids

and here is one at sunrise

What is amazing is that we can now see meteorites from the other side. These are Leonids seen from the space shuttle!

Meteorites are larger objects that his the ground. We see signs of this on almost every object in the solar system.
e.g Earth: this is the Manicougan crater in Northern Quebec: Note this is so large that it can only be seen well from space. ∼ 200 Million years old.

  • Much more important What killed the dinosaurs?
    Alan Hildebrand (GSC for a while) found a 65 million year old, 112 mile wide ring structure (the Chicxulub crater) still detectable under layers of sediment of the Yucatan Peninsula region of Mexico. Crater is consistent with the impact of an object of sufficient size (6 to 12 miles wide) to cause the global disruptions.

    This must have been an asteroid. Can it happen again?
    Apollo asteroids: cross earth's orbit (and may collide occasionally!) Eros used to measure Earth-Sun distance very accurately All small < 30 km radius
    Toutatis came within 1500000 km (4x distance of moon) last fall. Expect major collision ~ 100000 years
    (and a free cup of coffee to anyone who knows who Toutatis is!)

    COMETS

    The Hairy Stars: this is Arend-Roland
    Mostly very eccentric orbits, long periods, not in plane of ecliptic only visible near the sun.
    "Dirty Snowballs" H2O + dust + CO2 Water boiling causes breakup? Some comets observed to have jets, which can alter orbits

    Low mass, cannot retain gas (this is Mrkos)

    Breakup need not be just material being blown out behind: previous encounter can give rise to material in same orbit: this is Shumacher-Levy
    e.g. Arend-Roland
    Meteors are assumed to originate in comets which break up. e.g. the stuff left behind by Swift-Tuttle annually create the Perseids this is particularly bright every 33 years (tho. less so now). Perseid meteor in an aurora:

    Credit & Copyright: Jimmy Westlake, Colorado Mountain College)
    This is comet LINEAR,

    which was going to be quite spectacular

    However it didn't work out that way!

    THen it shattered into pieces!
    and finally it has just evaporated!
    Best close-up of a comet is of Wild: note the "outgassing". Diam is about 5 km

    Going Wild Credit: Stardust Team, JPL, NASA

    Other comets have different problems. Many start off with a very small velocity, so they fall almost directly towards the sun. The SOlar and Heliospheric Observatory (SOHO) has found 102 new comets.
    Most of the comets discovered with SOHO are "sungrazers". With the heat and tidal forces, they aren't going to survive their close passage.
    and here is another one that isn't going to make it!

    Where do comets come from?
    Most have very long periods: Great Comet of 1858 had period of over 100000 years, very few have many repeats, (Halley's comet at 76 years and ∼30 repeats is an exception)

    Oort cloud 105 A.U. from sun Perturbations by passing stars can start comets falling towards sun. No angular momentum, so must start from rest.

    (Parenthetical question: why are all comets about the same size: core of 10 km or so? Don't know!)

    Finally the most distant object we have seen:

    Sedna:

    Sedna is almost at its closest; 10,000-year orbit takes it into the Oort cloud. Probably not a planet in the usual sense.

    Credit: NASA/JPL-Caltech/R. Hurt (SSC-Caltech)
    What exactly is a planet? (Sedna and Quaoar are "objects")

    No easy answer: conventionally we take original 8 as planets, and say everything else is not (i.e. Pluto isn't).

    So where did the solar system come from....?