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WHAT ELSE CAN WE X-RAY?
The picture to the right shows a mosaic of X-ray photos of the centre of our
galaxy taken by Chandra, one of NASA’s X-ray observatories. The colours
are made up of red (low energy X-rays), green (medium energy X-rays) and blue
(high energy X-rays). The bright white spot in the middle is the stuff falling
into the giant black hole (don’t worry we’re too far away to be
in any danger!); however, you can also see hundreds of ordinary stars, lone
neutron stars, white dwarfs and hot gas.
The brightest thing in the X-ray sky is the Sun, because it is so close. The
X-rays are produced by gas that is more than a million degrees Celsius in the
corona of the star (the bit you can see during total eclipse- as seen in the picture). The gas is heated by the ever-changing magnetic fields of the star. Sometimes
a whole lot of energy can be released in one go as stellar flares; the star
can become hundreds of times brighter in X-rays during a flare! We can only
see X-rays from ordinary stars if they are relatively close (a few hundred light
years - still a long way.) For example the X-ray power of the Sun is the same
as about 50 power stations per person on Earth - and stellar flares can be 10,000
times more than this!
An X-ray view of the Sun.
(ISAS/Yokoh team/Lockheed)
The picture above shows an X-ray view of the Sun: you can see a huge amount
of detail as the X-ray hot gases in the Sun’s corona follow the fantastically
complicated magnetic fields. However, the Sun is about a million times fainter
in X-rays than in visible light; so for us to see other star systems in X-rays
they have to be doing something amazing. When X-ray astronomy took off - literally - in the 1960s , we found the universe to be more dynamic and extreme than
we’d ever imagined!
HOW TO LEARN MORE
If you want to learn more about the exciting secrets of the Universe that could
only be found by breaking free of the Earth, why not try your hand at courses
offered by the Open University.
Other places of interest can be found by typing into any decent search engine.
You'll find a wealth of information. Have fun!
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