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What does X-ray light show us?
Many things in space emit X-rays, among them are black
holes, neutron stars, binary star systems, supernova
remnants, stars, the Sun, and even some comets!
The Earth glows in many kinds of light, including the
energetic X-ray band. Actually, the Earth itself does not
glow - only aurora produced high in the Earth's atmosphere.
These aurora are caused by charged particles from the Sun.
 
Credit: Polar, PIXIE, NASA
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To the left is the first picture
of the Earth in X-rays, taken in March, 1996
with the orbiting Polar satellite. The area of
brightest X-ray emission is red. The energetic
charged particles from the Sun that cause aurora
also energize electrons in the Earth's
magnetosphere. These electrons move along the
Earth's magnetic field and eventually strike the
Earth's ionosphere, causing the X-ray emission.
These X-rays are not dangerous because they are
absorbed by lower parts of the Earth's
atmosphere. (The above caption and image are
from the Astronomy Picture of the Day for
December 30, 1996.) |
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Recently, we learned that even
comets emit X-rays! This image of Comet
Hyakutake was taken by an X-ray satellite called
ROSAT, short for the Roentgen Satellite. (It was
named after the discoverer of X-rays.) |
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The Sun also emits X-rays - here
is what the Sun looked like in X-rays on April
27th, 2000. This image was taken by the Yokoh
satellite. |
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