FIND
YOUR OWN CV!
Cataclysmic Variables have a whole repertoire of cool
ways to change their appearance, and best of all, you
can see them do it with an ordinary telescope, unlike
X-ray binaries. One of their favourite tricks is to
let the accreted matter accumulate and explode it all
off at once. Some of them blow off a little and often,
having an outburst every few months where the brightness
increases by a factor of about 10 for a few days: these
are called dwarf novae. Then there are the classical
novae, that are thought to explode only once every 3000
to 10000 years but become up to 100 million times brighter.
Amateur astronomers discover many new dwarf novae and
classical novae each year. The real fireworks happen
when the white dwarf piles on so much extra mass that
it collapses into a neutron star- the result is a second
type of supernova, like the brightest one ever in 1006.
HOW DO WE X-RAY THE UNIVERSE?
X-rays and Gamma rays are very high frequency light
that we cannot see - extremely dangerous to life. Luckily
for us, the Earth’s atmosphere protects us. But
unfortunately for astronomers, it does mean that we
need to put telescopes into space if we want to study
them. Early X-ray telescopes were sent up on rockets
and balloons for a couple of hours at a time, but nowadays
we use hi-tech satellites such as the European Space
Agency’s X-ray observatory XMM-Newton (see picture)
that run for several years. X-ray images such as shown
on page one are taken with CCD cameras, like very advanced
and expensive versions of the digital cameras available
today.
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