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Thread: Death by Hypernova?
May 28th, 2004 9:41 PM #1
- Join Date
- Nov 2003
Death by Hypernova?
Thanks go to Hans (Dutchie) who found this for me;
- - -I would direct a reader's attention to that part of this paper that describes what could possibly happen to our satellites after a blast from this, which COULD knock them out with a gamma-ray burst, EVEN from this vast a distance. . . (could this ALSO prove to be another piece to the "Aussie Bloke" puzzle?)
Southern skywatchers this time of year can look up and see the most
interesting and enigmatic star in the sky -- a star of a type so remarkable
that only a few dozen examples are known. That star is Eta Carinae, and it
may also be the most dangerous star in the sky.
The reason for the danger is that Eta Carinae is like a nearby volcano
waiting to explode, but we don't know when. In the last few months, however,
it has shown signs of new activity and it has astronomers riveted on its
The burning fuse
To astronomers there are two things immediately obvious about Eta Carinae:
It is amazingly, almost impossibly bright, shining 4 million times brighter
than our sun. It is also wildly unstable, being prone to huge flares,
outbursts and dizzying swings in brightness that give the impression of
something on the verge of self-destruction - which it may well be
What causes all this strange behavior in Eta Carinae is very simple: It's
enormous, more than 100 times the mass of our sun. On Earth we tend to think
of large things as being solid and stable, but in stars of this size the
opposite is true. Their large size causes them to burn their nuclear fuel at
an extremely rapid rate, blasting out so much heat, light and other energy
that their outer layers are shredded, roiled and sometimes completely blown
off in repeated violent outbursts.
The blast in the past
It was just such a violent outburst that first brought Eta Carinae to the
attention of astronomers almost two centuries ago. It was first catalogued
in 1677 as an unremarkable star, barely noticeable to the naked eye. But by
1730 observers noticed that Eta Carinae had grown much brighter, having
become one of the most prominent stars in its constellation.
By 1782 it had dimmed to its former obscurity, but then in 1820 it again
started growing and growing in brightness. By 1827 it had brightened more
than tenfold, and by 1843 it was blazing as the second brightest star in the
sky, outdone only by the star Sirius, which is 1,000 times closer to us.
At the time, no one understood what could possibly cause such strange
behavior in a star, and it wasn't until 1994 that the Hubble Space Telescope
first revealed what had happened 150 years before: Eta Carinae had blasted
out an enormous two-lobed bubble of hot, glowing gas. Even today it can be
seen racing outward at one and a half million miles per hour (2.4 million
kilometers per hour). The amount of material blasted out was enough to make
several of our suns, but for Eta Carinae it was just the latest outburst in
its short and violent life.
The end of a short life
Eta Carinae is destined to die young. Most stars live for billions of years,
but stars as massive and active as Eta Carinae burn through their fuel in an
extremely short time -- as short as one million years or so, very quick for
a star. They almost always end the same way: With a supernova explosion, a
massive detonation that blows the star apart and scatters its remains for
trillions of miles (kilometers) around.
That's how most supermassive stars end, but Eta Carinae is such an extreme
case that another possibility exists: It could end as a hypernova, a
super-supernova that at its peak will outshine the entire galaxy.
The blazing violence of such an event is difficult to describe. Were it much
closer it could even wipe out all life on Earth, eradicating our thin
biosphere just like an ultraviolet lamp kills microbes. Fortunately it's not
that close, but at 7,500 light-years it's still close enough to do some
However, the likely damage is not to humans directly, but to satellites and
the upper atmosphere. That's because an explosion of this type generates
huge amounts of high-energy radiation such as gamma rays. We on Earth are
well shielded from gamma rays by our atmosphere, but satellites in space
would be vulnerable and some of their electronics could be damaged by such
Some have speculated that a huge blast of gamma rays could also affect the
upper atmosphere, including the ozone layer. But that remains only
speculation, and any such effect is likely to be very transient because the
blast of gamma rays would be fairly brief.
The only humans who might suffer directly from Eta Carinae's violent demise
would be astronauts in space. Outside of the Earth's protective atmosphere
they would be subject to the same powerful radiation as satellites, with
conceivably lethal effect. While our own sun is also capable of lethal
emissions, such as coronal mass ejections that could be harmful to
astronauts, the difference is that our sun's eruptions usually give us some
warning, whereas Eta Carinae would not.
Current warning signs
What now has astronomers thinking again about Eta Carinae's ultimate end is
what has happened since 1998: It has suddenly started brightening again,
more than doubling in brightness in the last 18 months.
This sudden change was completely unexpected. The leading theories on Eta
Carinae held that it had entered a more stable phase during which it would
very slowly brighten as the dust cleared from its last outburst. But instead
it shot up in brightness in a very short time, and it continues to brighten
while the theorists puzzle out what could be happening.
The star we've never seen
What makes the puzzle particularly difficult is that we have never actually
seen Eta Carinae. When we look toward Eta Carinae or photograph it, what
appears is not the star itself, but the huge shroud of glowing gas and dust
it has thrown up around itself.
The glowing shroud around Eta Carinae has led some to speculate that behind
the shroud lies not one star, but two or more massive stars combining to
shine so brightly. But that still doesn't explain the burning question of
the moment: What has happened to Eta Carinae in the last few months, and
what will happen next?
No one really knows. Like geologists watching a trembling volcano, all we
can do is watch and wait.
Eta Carinae could blow anytime, or it could continue rumbling and spewing
gas until the day, perhaps tomorrow, perhaps thousands of years from now,
when it will suddenly let go with the most phenomenal display of violence
ever witnessed by humans. It is now being watched almost around the clock,
as much for the fascination as the science.
But perhaps the ultimate knowledge we can gain from Eta Carinae is not about
stars, but about ourselves: That on the grand scale of creation, we are puny
creatures indeed, and fortunate to have such a protective abode. The grand
universe is fascinating, but there's no place like home.
- - -Submitted by Joe (Bigsky770)
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