Download Kristen Turiano

Kristen Turiano
4-26-2010
Astronomy
Fact Sheet
Comets
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an icy body that releases gas or dust.
Most travel around the sun in long, oval orbits.
consists of a solid nucleus (the core)
cloudy atmosphere called the coma
one or two tails.
most are too small or too faint to be seen without a telescope.
Some can be seen for several weeks as they pass close to the sun.
the gas and dust in their comas and tails reflect sunlight.
gases release energy absorbed from the sun, causing them to glow.
classify comets according to how long they take to orbit the sun.
Short-period comets = less than 200 years to complete one orbit
long-period comets = 200 years or longer.
Belief that comets are leftover debris from a collection of gas, ice, rocks, and dust
that formed the outer planets from about 4.6 billion years ago.
Belief that comets originally brought some of water and carbon-based molecules
that make up living things to earth
Parts of a comet
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Nucleus = ball of ice and rocky dust particles (dirty snowball)
ice consists mainly of frozen water but might have other frozen substances
(ammonia, carbon dioxide, carbon monoxide, and methane)
belief that nucleus of some comets might be fragile because many comets have
split apart for no apparent reason.
heat from the sun vaporizes some of the ice on the surface of the nucleus, spewing
gas and dust particles into space.
This gas and dust forms the comet's coma
Radiation from the sun pushes dust particles away from the coma.
This forms something called the dust tail
the solar wind ( the flow of high-speed electrically charged particles from the
sun) converts some of the comet's gases into ions
These ions stream away from the coma and form an ion tail
The tails always point away from the sun because they are formed by solar
radiation
Most comets have an estimated nucleus that measures about 10 miles (16
kilometers) or less across
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Some comas can reach diameters of nearly 1 million miles (1.6 million
kilometers).
Some tails extend to distances of 100 million miles (160 million kilometers)
Life of a comet
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short-period comets come from a band of objects called the Kuiper belt
kuiper blet lies beyond the orbit of Pluto
gravitational pull of the outer planets can nudge objects out of the Kuiper belt
they become active comets in the inner solar system
Long-period comets come from the Oort cloud
The Oort cloud is a nearly spherical collection of icy bodies about 1,000 times
farther away from the sun than Pluto's orbit
Gravitational interactions with passing stars can cause icy bodies in the Oort
cloud to enter the inner solar system and become active comets.
Comets lose ice and dust each time they come back to the inner solar system
This leaves trails of dusty debris
The debris become meteors that burn up in the atmosphere.
Eventually, some comets lose all their ices
They break up and dissipate into clouds of dust
The study of comets
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Scientists learned a lot about comets by studying Halley's Comet
Halley’s Comet passed the earth the first time in 1986
Five spacecrafts flew past the comet to collect information about its appearance
and chemical composition
There were many probes that got close enough to study the nucleas
The nucleus was potato-shaped that measured about 9 miles (15 kilometers) long.
The nucleus contains equal amounts of ice and dust
About 80% percent of the ice is water ice
Other 15% is frozen carbon monoxide
The rest contains frozen carbon dioxide, methane, and ammonia
Belief that other comets are very similar to Halley’s Comet
Halley’s Comet’s nucleus is dark black
Belief that surface of this comet (and others) is covered with a black crust of dust
and rock
Comets only release gas when holes are facing the sun
Other discovered comets
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Shoemaker-Levy 9 (crashed into jupiter)
Hale-Bopp (came close to earth, was so birght could see with the unaided eye)
Wild 2
Churyumov-Gerasimenko