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Bright Star Getting Brighter
jwhyche writes "Just what the heck is Eta Carinae doing? Well astronomers are not quite sure. After being one of the brightest stars in the Southern sky it dimmed for a few decades. Now it's back, emiting five time the energy of the sun, and is right next door. So, how big is a hypernova explosion anyways? Big boom anyone? "
Someone (I forget who) once theorized that the best way for aliens to contact us would be to modulate heavenly phenomenon in such a way that we would take note of it. For one, seeing as how we are constantly observing astonomical phenomenon, this would be a good way for the aliens to improve our chances of actually seeing the message, and two, we'd probably notice any glaring anomalies. So, Could this be the one? The SETI guys should sic their signal processing algorithms on the spectrum coming from this star.
~afniv
"Man könnte froh sein, wenn die Luft so rein wäre wie das Bier"
~afniv
"Man könnte froh sein, wenn die Luft so rein wäre wie das Bier"
Richard von Weizs
It's always fun watching the news media try to get astronomy right.
:-)=
Actually, I'm fairly impressed that there were only two glaring errors that were obvious without having read the press release or paper. The first was on the caption that shortened Eta Carinae to just "Eta". Ca ne marche pas. Eta Car would have been okay, but might have confused people?
The other one was a biggie, though. They say that hCar is about 100 times the mass of the sun (right) and shines 5 times brighter (wrong). I'm guessing what was actually said was either "10^5 times brighter" or "5 orders of magnitude brighter". Might also have been "5 magnitudes brighter", but that would only be 100x brighter, which wouldn't be right.
Still, if they're only off by a factor of 20,000, that's better than a lot of other astronomy news stories I've seen...
I cought this on cnn.com, and one of the things that truly amazed me was that the astronomers were publicly admitting that they didn't know what was happening.
You won't see many people admitting to the press that they don't have a clue. I mean when was the last time that you heard someone at any computer company say "Yep, that's a problem. Don't have any idea what it could possibly be"
Most of the time they'll deny that it exists, or just say, "oh, yes, we've been working on that at some time, expect a press release in the near future"
I'm just glad that _someone_ out there admits when they're wrong or clueless.
Here is a link. And another, and another. Funky!
-- What you do today will cost you a day of your life.
This isn't a very good article. Eta Carinae is merely the closest example of a class of stars known as Luminous Blue Variables (LBVs) which have been found in other galaxies and in the center of our own galaxy, obscured by dust.
When a massive star (more than thirty or forty times the Sun's mass) forms, the luminosity is so high that radiation pressure causes the star to lose mass. In the largest stars there is instability- the luminosity will sometimes increase to a few times its normal level and be emitted at shorter wavelengths humans can see, leading to a several hundredfold increase in visible radiation. This is accompanied by ejection of the star's surface layers.
Eta Carinae is believed to have been a bit brighter than it is now before around 1800, and then it underwent an outburst for a few decades in the mid-nineteenth century, becoming the second brightest star in the sky for a while. The star then faded to the limits of human vision for a while and has recovered somewhat in the twentieth century.
The luminosity of Eta Carinae has (for the past couple of centuries, at least) been tens of thousands of times that of the Sun. Most of the energy is emitted in the far ultraviolet, and the star is also behind a thick screen of dust that blocks most of the light which is visible (around ten percent is believed to get through).
A conventional supernova explosion at this distance would be a very bright star, comparable roughly to the planet Venus (currently visible in the west just after sunset). Supernovae of comparable intensity were seen in 1006, 1054, and 1572, so this is not an uncommon event. Supernovae of this size typically result in a black hole. Since these are not terribly uncommon, the nearest example of a black hole is probably at a distance of only a few hundred light years. The local interstellar medium has been cleared out by a supernova shock wave recently which is believed to be in the Scorpius-Centaurus Association, a group of easily visible stars around 500 light years away.
There are some theories which suggest that maybe large systems might do something more exotic, such as conversion of several solar masses of material into energy by gravitational collapse. This is an attempt to explain bright flashes seen in gamma-ray bursters (you can see one for a few minutes in binoculars from a distance of billions of light years) without having to have the energy come out preferentially in one direction. This competes with other theories in which the energy output of gamma-ray bursters is beamed.
My guess is that gamma-ray bursters are not connected with LBVs because there should be a much higher rate of LBVs dying than observed gamma-ray bursts.
It already is an interesting show, although it would become less interesting if it goes nova as it will blind us for a while from seeing the nearby stuff which presently makes it so pretty. At least the southern hemisphere would get to see the bright light in the sky for a while.
We'd get some increase, but it would probably have to go supernova for a significant amount of radiation to get past our atmosphere.
Of course, a supernova would geneate a neutrino burst (most supernova models require it, or else the blast does not happen). I think we already have 300 neutrinos per cubic centimeter, and I don't know at what level they ...um.. become toxic.
... it happened thousands of years ago. Can't you find some real news? :-)
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Hypernova are approximately 100 times more powerful than supernova. This still gives a fudge factor of approximately 55 times. So it's equivalent to a supernova at a distance of about 750 light years. A supernova at this distance would be harmful, but again not a complete killer. It still wouldn't be healthy but nothing like a close up view of a supernova. Now if a hypernova went off within ~1000 light years, we would be completely screwed.
Of course if the hypernova are a factor of 10,000 times as energetic as a supernova we would be cooked. Though since it probably won't happen in the next millenium or so gives us plenty of time to advance and prevent this kind of thing from wiping us out.