DON'T FREAK OUT

[spectre]

http://spectrevision.net/2012/02/17/dont-freak-out/

'GUEST STARS'
http://www.time.com/time/health/article/0,8599,2106904,00.html
by Michael D. Lemonick / Feb. 16, 2012

When the sun finally dies some 5 billion years from now, the end will
come quietly, the conclusion of a long, uneventful life. Our star
will, in a sense, go flabby, swelling first, releasing its outer
layers into space and finally shrinking into the stellar corpse known
as a white dwarf.

Things will play out quite differently for a supermassive star like
Eta Carinae, which lies 7,500 light-years from Earth. Weighing at
least a hundred times as much as our sun, it will go out more like an
adolescent suicide bomber, blazing through its nuclear fuel in a mere
couple of million years and exploding as a supernova, a blast so
violent that its flash will briefly outshine the entire Milky Way. The
corpse this kind of cosmic detonation leaves behind is a black hole.
For Eta Carinae, that violent end might not be long in coming,
according to a report in the latest Nature. "We know it's close to the
end of its life," says astronomer Armin Rest of the Space Telescope
Science Institute and the lead author of the paper. "It could explode
in a thousand years, or it could happen tomorrow." In astronomical
terms, a thousand years might as well be tomorrow; as for a supernova
blowing up literally tomorrow, well, that's almost unheard of.

In 1843 Eta Carinae gave a hint that the end might be near when the
hitherto nondescript body flared up to become the second brightest
star in the sky, after Sirius. It stayed that way for 20 years or so,
then faded and left behind a majestic, billowing cloud of gas known as
the Homunculus Nebula. Eta Carinae lost some 10% of its substance in
this event, which astronomers now call a "supernova impostor," after
which it has returned to relative quiet — or what passes for quiet in
such an unstable object. Astronomers back in the day did the best they
could to observe the 20-year flare, but without modern instruments,
they couldn't really learn much. That has frustrated investigators now
just as it did then, since studying Eta Carinae in detail could tell
them a lot about what caused the outburst and maybe even help them
figure out when the inevitable supernova explosion is going to occur.

But as the Nature report makes clear, that understanding may now be at
hand. Using a fiendishly clever new observing technique, Rest and his
colleagues have been able to take readings of the original blast in
real time. "We can look directly at the eruption," says Princeton
astrophysicist Jose Prieto, a co-author of the report, "as it's never
been seen before." To understand how they did that, start with the
basic fact that light from the outburst sped away from Eta Carinae in
all directions. Some of it headed straight toward Earth to wow 19th
century astronomers. But some of it took a detour, reflecting off dust
clouds in interstellar space in what astronomers call a "light echo."
At least a bit of that echo was redirected toward Earth. The dust
clouds were so far from the star that the long-delayed light is only
now reaching us, and unlike in 1843, we now have the instruments to
study it.

It gets even better. The 1843 flare-up played out over 20 years, which
means the light-echo version will do the same. "We took observations
nine months ago," says Rest, "and we were looking at 1843. Now we're
looking at 1844. It's like a movie. It's really cool." (Of course, the
images are from 7,500 years before 1843 and '44, since that's when the
stellar event occurred; it just took 7½ millennia for the light to
reach us.) Better still, astronomers can see light echoes from a
variety of dust clouds, at varying distances from the star. That
creates detours of varying lengths, so they can see different phases
of the eruption all at once.

"The big puzzle," says Prieto, "is what caused the outburst. This star
has been studied to death with all sorts of telescopes, but no one
theory has ever been able to tell us what happened." It might have
been some sort of instability deep within the star itself, or the
blast might have been triggered by matter dumped on Eta Carinae by a
stellar companion. The good news is that the light-echo observations
will give theorists a trove of information to work with — and in the
next few years, says Rest, "we'll be getting more observations, and
they'll keep getting better."

If Eta Carinae is going to blow imminently, the obvious question is
whether Earth is in mortal danger. Fortunately, the answer is no. At
7,500 light-years, the intense radiation from even a powerful
supernova would lose its punch by the time it reaches us. All we'll
experience is the most spectacular light show in many centuries. The
last confirmed supernova explosion in the Milky Way happened in 1604,
a teasingly close five years before Galileo pointed his first,
primitive telescope skyward. It is, in short, about time for another
big blast, and even though the theorists haven't weighed in, Rest has
reason for hope. "There was one of these 'supernova imposters' in
another galaxy," he says — something similar to Eta Carinae's 1843
outburst. "And then, a few years later ... kaboom!"

SECOND SUN
http://io9.com/5738542/earth-may-soon-have-a-second-sun
Earth may soon have a second sun
by Alasdair Wilkens / Jan 20, 2011

The red supergiant star Betelgeuse is getting ready to go supernova,
and when it does Earth will have a front-row seat. The explosion will
be so bright that Earth will briefly seem to have two suns in the sky.

The star is located in the Orion constellation, about 640 light-years
away from Earth. It's one of the brightest and biggest stars in our
galactic neighborhood - if you dropped it in our Solar System, it
would extend all the way out to Jupiter, leaving Earth completely
engulfed. In stellar terms, it's predicted to explode in the very near
future. Of course, the conversion from stellar to human terms is
pretty extreme, as Betelgeuse is predicted to explode anytime in the
next million years. But still, whether the explosion occurs in 2011 or
1002011 (give or take 640 years for the light to reach Earth), it's
going to make for one of the most unforgettable light shows in our
planet's history. For a few weeks, the supernova will be so bright
that there will appear to be two stars in the sky, and night will be
indistinguishable from day for much of that time. So don't count on
getting a lot of sleep when Betelgeuse explodes, because the only
sensible thing for the world to do will be to throw a weeks-long
global supernova party.

Physicist Brad Carter explains what Earth (and hopefully humanity) can
look forward to:

"This is the final hurrah for the star. It goes bang, it explodes, it
lights up - we'll have incredible brightness for a brief period of
time for a couple of weeks and then over the coming months it begins
to fade and then eventually it will be very hard to see at all."

Although there'll be no missing the explosion, Carter points out that
the vast majority of material shot out from the supernova will pass by
Earth completely unnoticed:

"When a star goes bang, the first we will observe of it is a rain of
tiny particles called neutrinos. They will flood through the Earth and
bizarrely enough, even though the supernova we see visually will light
up the night sky, 99 per cent of the energy in the supernova is
released in these particles that will come through our bodies and
through the Earth with absolutely no harm whatsoever."

Indeed, just in case anyone is concerned, Betelgeuse is way too far
away from Earth to do us any damage. There's been some doomsday
speculation of late around the eventual supernova - which might not
happen for a million years, it bears repeating - but, as with pretty
much all doomsday speculation, you can just ignore it. In any event,
the Betelgeuse explosion will likely be the most dramatic supernova
Earth ever witnesses - well, unless our Sun eventually explodes and
destroys our planet, which would probably leave Betelgeuse the runner-
up. Either way, it isn't the first, as history has recorded the
appearance of several so-called "guest stars." Most of these just
looked like short-lived stars in the night sky, but some were bright
enough to be seen in the day.

The first supernova that history records is thought to have occurred
in 185 CE, when a star 8,200 light-years away exploded. Chinese
astronomers make explicit note of the sudden appearance of a star and
its subsequent disappearance several months later, and the Romans may
also have made more cryptic references to it. Astronomers have since
located the remnants of the exploded star, confirming the accuracy of
the ancient accounts.

The two most dramatic supernova explosions occurred in the 11th
century. A supernova in 1006 - you can see its modern remnant above -
is the brightest star ever recorded, appearing in the records of
China, Egypt, Iraq, Italy, Japan, and Switzerland. There's even some
thought that a rock painting by the Hohokam, a Native American tribe
in what is now Arizona, represents the first recorded sighting of a
supernova in the Americas. Here's the petroglyph in question, which
might well record the presence of an unexpected bright light in the
sky:

The various observations even allow us to pinpoint what specific type
of supernova it was. In all likelihood, it was a Type Ia supernova,
which for a few weeks burn as brightly as five billion suns.
Astronomer Frank Winkler explains that we can work out from that
supposition:

"By knowing this distance and the standard luminosity of Ia
supernovae, we can calculate, in retrospect, just how bright the star
must have appeared to 11th century observers. On the magnitude scale
used by astronomers, it was about minus 7.5, which puts its brightness
a little less than halfway between that of Venus and that of the full
Moon. And all that light would have been concentrated in a single
star, which must have been twinkling like crazy. There's no doubt that
it would have been a truly dazzling sight. In the spring of 1006,
people could probably have read manuscripts at midnight by its light."
The supernova of 1054 wasn't quite as dramatic, and it seemed to go
almost entirely unrecorded in Europe, although there's some thought
that records of the new star made by Irish monks got corrupted into
allegorical accounts of the Antichrist. Still, the rest of the world
saw it just fine, with records popping up in China, Japan, Korea,
Persia, and the Americas. Astronomers of the time period wrote that it
could be seen in daylight for over three weeks and remained visible in
the night sky for nearly two years.

A pair of supernovas in 1572 and 1604 were extensively studied by two
generations of legendary astronomers, Tycho Brahe and Johannes Kepler.
Since then, the Milky Way hasn't had any supernovas visible from
Earth, and so our night sky has remained rather tediously ordinary.

There's about sixteen known candidates in our galaxy for a future
supernova explosion, and quite a few of them would have a dramatic
effect on our skies. But Betelgeuse is by far one of the closest, and
its huge size means its explosion will be particularly dramatic. This
is one cosmic disaster that we actually want to see happen sooner than
later, because there may never be a sight quite like this ever again.