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."

Comments

Rho Casspiopiae

[9x320]

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)

Re:Rho Casspiopiae

[SetupWeasel]

Giant stars do not produce type 1a supernovae. Type 1a SN are believed to be caused by a binary system of a giant star and a white dwarf. When the one star becomes a giant, the atmosphere can be so large that it fills its gravity well and spills material onto the white dwarf. The white dwarf, which would never be massive enough to become a supernova on its own, gains the mass from its partner at a trickle until it reaches the mass necessary for it to collapse.

Because type 1a SN are believed to occur under nearly identical circumstances, they are considered especially important in astronomy. Astronomers believe that they can be used as what they call "standard candles." A "standard candle" is a light source of known brightness. Standard candles are important, because astronomers can directly determine the distance of these sources. Certain stars already act as standard candles, but stars can only be resolved at a certain distance. A type 1a SN can be seen at such a large distance that astronomers believe they can more accurately determine cosmoloigical properties if they can determine exactly how bright one is, and how it may fluctuate under different circumstances.

Other SN are interesting, but a Type 1a SN in our galaxy might tell us a lot about the entire universe indirectly.

Re:Actually

[Is0m0rph]

They mention the star by name many times in the article. Did you actually read it? They mention it in the first few sentences. Here's the wiki on the star: http://en.wikipedia.org/wiki/RS_Ophiuchi

Re:Actually

[Zocalo]

Actually, they do name the star. It's RS Ophiuchi which is 1,950 light-years from Earth according to the linked Wikipedia article. It's worth a look if you are now thinking of doing some amateur astronomy since it also contains some information on some of the star's past failures at going nova and a bunch of related links.

Re:CNN Story is different...

[Phanatic1a]

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.'

Re:Range of lethality

[zepol]

While this doesn't directly answer your question, you might find the following interesting. Steven Dutch, a professor at the University of Wisconsin at Green Bay has estimated what would happen if the sun were to go supernova. Some highlights: the radiation flux on the daylight side of the earth would be the same as if our entire nuclear arsenal were to go off once per second at a distance of one kilometer. The reflected light from the full moon would be 10,000 times brighter than the sun; Venus would shine six times as intensely as the normal sun. The earth vaporize in a matter of days.

By the way, the sun will never become a supernova. The calculations are illustrative only.