Download Comet - Physics

Goal: To understand what comets are
and to explore the Oort cloud.
Objectives:
1) To learn about what comets are
2) To understand where comets come from
3) To explore what comets are made of
4) To examine the different tails of comets
5) To understand the evolution of comets
6) To Explore Aurora
7) To examine satellites
What is a comet?
• Try to think deep here…
• Draw a picture too.
What is a comet?
• Size
• Structure
• Orbit
Where do comets come from?
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Short period comets (periods < 300 years):
Option 1: When 2 icy TNOs collide.
A debris cloud will be formed.
This “debris” cloud will have several rubble
piles which are a few km in size.
• These rubble piles will travel in random
directions. Some will fall in towards the
sun.
Short period comets – cont.
• Usually they will start with an orbit which takes
them to the gas giant region. Here the objects
will be called Centaurs.
• Eventually these Centaurs will have a close
encounter with a gas giant (don’t worry Jupiter, I
won’t name any names).
• At this point they either collide with the planet
(like the Shoemaker-Levy 9 comet), or a moon
of the planet, or they are tossed into the inner
solar system.
Short period comets – option 2
• Have a close encounter with Neptune.
• This can toss it into an orbit which goes
from Neptune to the orbit of the terrestrial
planets (like Earth).
• Or, it could become a Centaur for awhile.
Meteor Showers
• Occur when the earth passes through the
orbit of a short period comet
Long period comets
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Orbits are millions of years.
None come from interstellar space.
These come from the Oort cloud.
Collisions are a possibility, but more than likely
these orbits started this way (we will see how
later).
• Although collisions are possible, they are not
likely. There is just too much space out there.
• The only other way to go from circular orbits to
extremely elliptical ones is to have perturbations
from passing stars (stars that occasionally get
within about 0.5 light years from the sun).
Structure of comets (APOD – Bradfield + LINEAR)
Hale Bopp + Andromeda (APOD)
Nucleus – comet Borrelly (APOD)
Deep Impact – Temple 1
After
impact
Wild 2 (Stardust)
Halley’s nucleus (APOD + Giotto)
• 6 m deep of material thrown off each pass
• Cause of the Orionids meteor shower.
• 15 km in size, Density 25% of water. Very dark
nucleus.
apart
What is the fate of comets?
• Eventually, comets eject all their icy
material near their surfaces.
• When this happens, they look more like
metal poor asteroids.
• So, they stop being “comets” like we know
them, and are just a floating rock pile with
some ice in the center quietly floating
through the solar system in its orbit.
Aurora
Satellites
• https://www.youtube.com/watch?v=x8YDR
nZzyNs
• https://www.youtube.com/watch?v=dfGGA
_apXic
conclusion
• Comets are mostly loosely held together
piles of ice and rock (“dirty snowballs”).
• Comets light up when they get inside the
orbit of Mars because they eject several
meters of ice off their surfaces through
jets.
• Short period comets probably come from
the Kuiper Belt.
• Long period comes probably are the Oort
Cloud.