Understanding Comet Overview, Composition, and Facts.
                     Understanding Comet: Overview, Composition, 
and Facts
Introduction
• Comets are frozen leftovers from the formation of the solar 
system composed of dust, rock and ices. 
• They range from a few miles to tens of miles wide, but as 
they orbit closer to the sun, they heat up and spew gases and 
dust into a glowing head that can be larger than a planet.
Source: solarsystem.nasa.gov
Composition
• Nucleus: relatively solid and stable, mostly ice and gas with a 
small amount of dust and other solids;
• Coma: dense cloud of water, carbon dioxide and other neutral 
gases sublimed from the nucleus;
Source: nineplanets.org
Composition Cont.
• Hydrogen cloud: huge but very sparse envelope of neutral 
hydrogen.
• Dust tail: up to 10 million km long composed of smoke-sized 
dust particles driven off the nucleus by escaping gases.
• Ion tail: as much as several hundred million km long 
composed of plasma and laced with rays and streamers 
caused by interactions with the solar wind.
Source: nineplanets.org
Interesting Facts about Comet
Comets come from the Kuiper 
belt and the Oort Cloud
• These areas of space are way out in the solar system far away 
from the Sun. The Oort cloud is so far away we have never 
even seen it. 
• The comets visible from Earth are most likely ones that came 
from the closer Kuiper belt which is near Pluto.
Source: nineplanets.org
There are millions of comets, 
and they are all orbiting the Sun
• Most take less than two hundred years to do so, and others 
travel much slower, potentially taking millions of years to 
complete an orbit.
Source: nineplanets.org
Comets spend most of their years 
in the Kuiper belt and Oort cloud
• Every now and again two comets can crash into one another. 
When this happened, they often change direction, and this 
can throw them out towards the inner solar system.
Source: nineplanets.org
When a comet approaches the inner 
planets, it is warmed by the Sun
• When this happens, it begins to melt and throws out dust and 
gas. This creates a head and the tail. 
• The tail is the part of the comet we see in the sky. The tail 
always points away from the Sun. 
• This means that sometimes the tail is behind the comet and 
sometimes it in front. 
• It all depends on whether the comet is travelling towards or 
away from the Sun.
Source: nineplanets.org
The most famous comet of all 
time is Halley’s Comet
• Halley is a periodic comet and is visible from Earth every 76 
years and has been for centuries. It made its last appearance 
in 1986. 
• Other famous comets include the Hale-Bopp Comet, Donati’s 
comet and the Shoemaker-Levy 9 Comet.
Source: nineplanets.org
Thank You!