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 bright 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 be will 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.
via NEWS.com.au; artist's conceptions of Betelgeuse explosion via AstroRed and CBC News]
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