Ask Me Everything3

Why do comets

have tails?

* *

4

For most of its lite, a comet is just a lump of snów and dust orbiting through space. But if its pa-th takes it close to the Sun, the heat turns the snów to gas and in the process releases dust. This forms two tails that make the comet easily seen from Earth.

Comets

01: Measuring a couple of miles across, the heart of a comet is an irregular-shaped spinning dirty snowball called a nucleus.

02: Trillions of comets orbit the Sun beyond Neptune, but only those that travel into the inner solar system develop a coma—a huge spherical head of gas and dust, with gas and dust tails.

03: Gas molecules absorb sunlight, fluoresce, and produce a bluish gas taił. Dust particles just reflect light, and the dust taił appears white.

04: The size of the

coma and tails depend on how close the nucleus gets to the Sun. The tails can be up to 62,137,000 miles (100,000,000 km) long.

How to:

land on a comet

I ■ Launch a spacecraft to a comet. The European Rosetta spacecraft is already on its way to meet Comet Churyumov-Gerasimenko.

Comets ae ^_nTncS»ged"

4.6 bffion years ag _Juplie, and the region bet "_en pspersed Neptune ^and , _nai influence ot

W'^he9,'eS The comets that

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° malohS¹* e°isted.

Produce a

detailed map of the nucleus. Rosetta’s instrument’s will do this and monitor the way the comet loses materiał.

02.

04,

Orbit the nucleus of the comet. In 2014, Rosetta will meet up with the comet outside the asteroid belt and will then stay with it as it nears the Sun.

03

Release a probe to the comet’s surface. Rosetta’s probe Philae will anchor itself to the dusty snów.

Undertake some experiments. Philae will drill into the surface of the comet and analyze its composition.

WHAT’S IN A N AME?

was discovered in 199 by Alan Hale ana Thomas Bopp-

lAihat ab out ino?

Comets visible    “S fom

^aP riecade Smcularly easy to see

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