Goal: To understand what comets are and to explore the Oort cloud. Objectives: To learn about what comets are To understand where comets come from To explore what comets are made of To examine the different tails of comets To understand the evolution of comets To Explore Aurora 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? 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 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=x8YDRnZzyNs 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.