This is the item for notices and discussion of cosmic phenomena,
aka astrophysics.

2 responses total.

One recent event that made the news:  the magnetar explosion last year.
It was so powerful, from 400 light years away it had a strong influence
on the Earth; it turned "night" into "day" as far as the ionosphere was
concerned.
 
What's a magnetar?  Glad you asked...
 
When a heavy star runs out of nuclear fuel and blows up as a supernova,
it leaves behind much of its mass as either a black hole or an ultra-dense
core called a neutron star.  Neutron stars pack the mass of a couple of
Suns into a ball a few miles across; because the incredible pressure
shoves most of the electrons and protons together, they are made mostly
out of neutrons (thus the name).
 
Most neutron stars have a magnetic field, and pretty much all of them
spin.  When a fast-spinning neutron star's magnetic field interacts with
the surrounding medium, it emits radio waves in step with its rotation;
such stars are called pulsars.  In the process, it slows down.  Some
pulsars are spinning almost as fast as a thousand revolutions per SECOND!
However, these ultra-fast pulsars have very weak magnetic fields.  They
have to, in order to remain spinning at those high speeds for long enough
to be seen in our fleeting human lives.  Most pulsars spin much slower,
at a few revs/second to a few seconds/rev.
 
For some time, astrophysicists have postulated the existence of neutron
stars with immense magnetic fields.  These magnetic stars, or magnetars,
would brake themselves very strongly against the medium around them.  By
the time the shell of their own supernova explosions had cleared away,
they would be turning too slowly to be seen as pulsars.  Their normal
X-ray glow would be very hard to see against the background of the galaxy.
And so they remained merely theoretical entities, with no examples known.
 
Until one night last year.
 
At that time, a huge blast of soft X-ray radiation came from a source
400 light years away.  Even at that distance it was as powerful as the
Sun's normal ionizing emissions, and ionize it did.  The ionosphere
on the size of the earth facing the blast experienced "day"; the
long-distance radio skip in the AM radio band disappeared, turning
global broadcasters into local-only stations in an instant.
 
This radiation came from a magnetar in upheaval.  In the process of
compression or turbulence, the magnetic fields in a star (including
our Sun) can become tangled and stressed.   When those fields get the
chance to un-tangle themselves, they release quite a bit of energy;
on the Sun, this causes solar flares.  Consider the forces needed to
pull two powerful magnets apart, and how much energy it takes.  Now
ponder the energy involved in fields millions or billions of times as
strong threading through a body miles across, and remember that forces
and energies are proportional to field strength *squared*...
 
Un-tangling the magnetic fields always re-arranges the matter they're
going through.  On a magnetar, this means throwing around large volumes
of stuff that weighs a billion tons per tablespoon, and doing it at a
large fraction of the speed of light.  This generates cosmic amounts
of HEAT.  Not thousands of degrees, but tens of millions of degrees.
At these temperatures matter radiates X-rays intensely, powerfully 
enough to rival a normal star's output from 25 million times as far
away.  This glow, invisible to the eye, brought daytime to the 
ionosphere on the night hemisphere of Earth.  For a few short minutes,
the nearly-invisible magnetar was among the brightest objects in our sky.
 
Not that you'd have noticed if you weren't monitoring the shortwave or
something, but it was some storm we had, eh?

Another big event in the last few months was a huge gamma-ray burster.
 
Gamma-ray bursters are very mysterious things.  Nobody knows what they
are.  They seem to appear all over the sky; unlike stars, they do not
cluster around the outlines of galaxies.  This suggests that they are
scattered all over the universe, up to billions of light-years away.
From this distance, they are briefly the most powerful sources of
gamma rays in the sky.  Then they fade, possibly never to repeat.
Two GRB's have never been observed from the same location.
 
They are also extremely small, by cosmic standards.  The pulses from
GRB's rise and fall in a matter of seconds.  This means that they
can be no larger than a few light-seconds across.  For example,
the orbit of the Moon is about 2.5 light-seconds from one side to
the other.  This means that most gamma-ray bursters, for all their
cosmic power, could probably fit inside that circumference!
 
GRB's were first observed in the 60's, when satellites launched to
watch for (banned) nuclear tests in space immediately began picking
up pulses of gamma rays from outside the solar system.  Recent satellites
have had experiments designed specifically to get data about GRB's, and
in the last few months an early-warning network was set up to provide
fast notice of a new burst and its location in the sky.  This data could
get other telescopes pointed at the same location in a hurry.  The hope
was that visible light from the burst might be seen before it faded, and
give new information (e.g. spectroscopic observations) which could
help determine what these mystery objects are.  Some observations had
caught the glowing embers, but nobody had caught one in the act.
 
On January 23, this changed.  NASA's ROSAT saw the beginnings of a
burst in the constellation Bootes, and sounded the alarm.  22 seconds
later, a robotic telescope at the Los Alamos National Laboratory was 
on-point and observing.  What it saw was nothing short of amazing.  The
spectra showed that the burster was in a galaxy some 9 billion
light-years away.  Across that vast reach it delivered the strongest
gamma-ray burst ever recorded, exceeding even the burst dubbed The
Second Big Bang.  The visible remnant was no slouch either; had anyone
been looking, they would have been able to see it quite plainly with
mere binoculars!  The cosmic fireworks lasted just under two minutes.
 
A supernova gives off its energy over weeks and months; this burst
radiated the energy of 2,000 supernovae in only 100 seconds.  A
supernova shines as bright as a whole galaxy; this burster was briefly
as bright as a million galaxies.  Or maybe not; the brightness at
Earth may have been greatly enhanced by a phenomenon known as
gravity lensing.  Even so, it was something to write home about.
(And if it was we may get another chance to see it, as an "echo"
pulse comes to us around the other side of the lens.)
 
What the heck ARE gamma-ray bursters?  We still don't know.  One
of the candidates theories says they are the merger of two orbiting
neutron stars (consider two magnetars tangling, with orbital speeds
of half of c and immense gravity for power sources).  If that is
true, the core of a GRB would fit comfortably between Ann Arbor and
Detroit (comfortably for it, if not us).  Whatever they are, catching
these pyrotechnic displays in the act appears to be the key to
understanding them.

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