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Astronomers Awaiting 1a Supernova
Aryabhata writes to tell us BBC News is reporting that astronomers have sighted a star on the brink of a "1a" supernova. This opportunity presents the first chance astronomers have ever had to view a supernova of this magnitude up close. From the article: "They are so rare that the last one known in our galaxy was seen in 1572 by the great Danish astronomer Tycho Brahe, who first coined the term nova, for "new star", not realizing he was in fact witnessing the violent end of an unknown star. It has long been believed that type 1a supernovae are the death throes of a white dwarf star. But all modern ones have been so distant that it has not been possible to see what had been there beforehand."
It happened long ago and the light is just now reaching us.
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Any decade now.
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From TFA:
But soon, RS Oph could pass the tipping point - the nuclear flame will detonate from deep inside the star and blow it apart. How soon is not clear.
"It could be tomorrow, but most likely it'll be 1,000, 10,000, 100,000 years from now," says Jeno Sokoloski.
Wow that's some long life astronomers. I wonder if they will be around to see DNF getting release.
Stupid headline.
version 1a? They aren't even in beta yet!
Monstar L
Rho Casspioiae is supposedly near the brink of explosion, too, and aside from that, I remember hearing about some luminous supergiant or hypergiant expected to explode in the same constellation, Casspioia.
Coincidentally, two other supernovas have ocurred in that area, one of which was the one Tycho Brahe saw. Keep an eye on the hypergiants (see: Wikipedia's explanation of how stars are classified)
I took Computer Science as a Humanities subject in college. My girlfriend took it through science. The CS courses feature the same modules, but she was able to take Astrophysics, while I took English. We both consider outselves to have a scientific leaning, though I wouldn't consider myself a "scientist" and she would.
/. blurb and was bouncing (literally!) with excitement, saying "they are reporting it now, so most likely it will be in ten, twenty years - within reasonable research time". I read it and my initial thought was that these reports are being made by science types. That means that this supernova will most likely occur in about 10,000 years, but that some scientist, in a lab somewhere, has just had the bright idea of pushing his research into the media spotlight, where it should (he hopes) be interesting enough to secure him a few more years worth of funding.
...astronomers will be studying the star closely, to watch its every step towards destruction, and hoping to understand the full details of one of the heaven's great mysteries". *sigh*
She read the
From the article: "How soon is not clear [but]
My girlfriend's lack of cynicism aside, this is one of my major problems with the science community. So much is driven by a desperate need to secure funding, that science "news", most of the time, is either hypothetical, theoretical, or so far in the future that it makes no difference to the present. In these cases, when a person finds out that no actual advance has been made, he feels both disappointed and betrayed.
I am fed up with reading...
"Newsflash: No physical reason humans cant live to be 300, once the technology arrives!" *
or
"Newsflash: the universe *might* be made up of string!" *
or
"Newsflash: in 100 billion years, this star will explode!" *
etc, when the invisible postscript to every story is:
* Now that I have your attention, please give me some more funding!
That's a NOVA, when the accumulated mass around a white dwarf in a binary system is launched outward, which the star regularly does. This would be a SUPERNOVA, when the white dwarf within the binary system actually explodes from within.
"Space is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." -- the Hitchhiker's Guide to the Galaxy.
Not only are the distances vast, the times are vast too. Stars live for billions of years. One year in the lifespan of a human is roughly comparable to perhaps 70 million years in the lifespan of a star.
So when someone says "soon" in reference to a prediction of when some stellar event is going to occur, it's likely you'll have to scale up the term by roughly the same amount. "Soon" to a human generally means within/around a day or so, so scaled up to stellar times, that would be within/around 200,000 years.
I expect that by the time this supernova happens, humans will either be unbelievably technologically advanced, or they'll be extinct.
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...that we have observed. The key answer is, that we have observed.
The radius of observation of these kinds of things is substantially smaller than infinite. Especially when you consider that earlier periods had a lower capability of observation.
So, really, we're talking about a fairly finite range of space and time in which supernovas would have to occur for them to be human-observable.
I've never seen a star go supernova before. But if it's anything like my old Chevy Nova, it'll light up the night sky!
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Shit.
So that would be like eating a vindaloo and lighting farts.
Nonono.
That's a nova. You've got a white dwarf, with a red giant companion star. Gas flows from the red giant to the white dwarf, accumulating there. Eventually enough builds up for fusion to begin in that accreted matter, and that causes a great increase in luminosity which we call a nova.
But that accreted mass doesn't disappear. Sure, some of it gets blown out into space, but the 'ash' of the fusion 'burn' accumulates with each cycle. Eventually, enough mass accumulates that the white dwarf star, in which fusion reactions have essentially stopped, becomes massive enough to start fusing the carbon that was created back when it was still on the main sequence.
So you have a sudden wave of carbon fusion that occurs everywhere throughout the star, causing an enormous increase in luminosity and also blowing the star apart. This is, not surprising, referred to as a 'carbon detonation' supernova, or Type 1a supernova, which is what the article was talking about. This thing's right under the critical mass at which that'll happen, so a bit more accumulation of stellar matter from its companion star, and 'boom.'
IANAExpertOnThisCrap, but... if the burst lasts less than 12 hours, at least a north-south slice of the planet would be spared. If it's just a few minutes, only half the planet would be "fried", and if the Pacific Ocean happens to be facing it, then it's only bad for the relatively small island population, but if Eurasia is facing it, that's gonna be really really bad.
Of course, that's based on the event being near the plane of the ecliptic. If the event was near a pole, then one of either the North or South hemispheres is fried, the other is spared.
I'm also assuming that the gamma rays aren't powerful enough to turn surface matter into radioactive isotopes that pollute the atmosphere and ocean, or to do that to the atmosphere itself. In that case, it's more proper to say that the Earth is poisoned, not fried.
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?
Not to rain on anybodies parade, but if that supernova sends a gamma ray burst in our direction. We can kiss our asses goodby.... ...and get new big, mean, and green ones.
I'm curious. At what range would a Type 1a supernova be lethal to life on Earth?
As far as the size of the galaxy is concerned, 1,950 light-years is essentially in our back-yard. Keeping with scale, are we talking about a firecracker or a stick of dynamite?
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I think your confusing types of radiation here. Gamma rays are electromagnetic radiation and will not create radioactive isotopes no matter how intense they are. Generally, what they are going to do is ionize atoms and heat things up. Damage to biologicals from Gamma rays is via ionization and heat effects.
If there were a very intense neutron burst, that could potentially "activate" some materials, i.e. transmute them into a radioacive isotopes. However, neutron burst are not going to be something we have to worry about at this distance from the event.
You are right that you can estimate stellar masses in binary systems by observing the system's orbital period. However, that is only useful for binary systems that are close enough for our telescopes to resolve (visually) the space between them. There are other, non-viusal methods that are used, but you basically have a limit on how far away a binary system can be for it to be observed in this way.
The utility of type 1a supernovae is that they are all produced by white dwarf stars exploding. White dwarfs are roughly earth-sized stellar cores that have no thermonuclear reactions going on inisde - they are the remnants of stars between about 1 and 5 solar masses after the outer layers have been blown off.
The imporant point is that the gravity of the stellar core's mass is not counteracted up by the pressure of the thermonuclear reactions inside. Rather, something called degenerate electron pressure holds the white dwarf up and prevents it from collapsing. Degenerate electron pressure can only counteract gravity for masses up to 1.4 solar masses, meaning that any white dwarf that somehow grows to a mass greater than 1.4 solar masses (usually by grabbing mass from a companion star), it will collapse. The collapse catastrophically increases the pressure inside the white dwarf, re-igniting nuclear fusion, and produces a sudden violent explosion.
Because white dwarfs are all of the same mass when they explode - 1.4 solar masses (the Chandrasekhar (sp?) limit - they are all of roughly the same brightness (>10^9 times as bright as the Sun). Because of this, one only has to see a type 1a supernova to deduce from the apparent brightness the distance from earth to the explosion. If a type 1a supernova occurs inside a cluster of stars, it conveniently tells us the distance from here to that cluster of stars. Because the distances over which supernova can be observed is orders of magnitude greater than most other stellar phenomena, the are essential in determining distances to faraway objects (from 1 to 1000 megaparsecs away (1 parsec = ~3.2 light years)). Distances to other galaxies are determined this way.
They type of supernova being observed can be determined by the specatra of light coming from it. I can't recall the distinguishing characterisitics of type 1a supernova, but suffice it to say they can be distinguished from other types of supernova.
The supernova that made the Cas A remnant is estimated at 1665AD or so. There was so much dust in the way that no one even saw it with the possible exception of the astronomer Flamsteed who recorded what he thought was a normal star there but when we look there today there's no star of the brightness Flamsteed saw. Dust can really dim a supernova so much that we don't see it, but since we're looking around with even neutrinos and radio that dust doesn't stop it'll be detected even if it's on the far side of the Galaxy.
Wikipedia lists ones occuring in our galaxy in 1006, 1054, 1181, 1572, 1604, and I remember from other sources that several were observed during Roman times.
Isn't that typical. Before the telescope, there was a frickin' smorgasboard of supernovae at close range, then no sooner does man invent the telescope and the party's over, which draws me to the conclusion: I blame this supernovae drought on Galileo.
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