Eta Carinae, Soon To Be a Local Supernova

da4 writes "Phil Plait over at Bad Astronomy has a great article about Eta Car, a star approx 7,500 light years away from us that's ready to supernova sometime Real Soon Now." Larger versions of the Hubble-Chandra image of Eta Car are available at the Chandra site. Of course when astronomers say it's "about to explode," they really mean it probably exploded 6,500 to 7,500 years ago and we're awaiting the news.

Comments

Ummm...

[TheSHAD0W]

All I can say is, if you see Al Gore, Michael Moore and Noam Chomsky wearing robes and riding camels... run like hell.

Re:Gamma Rays

[kenaaker]

The lobes in the picture show the path followed by the material from previous outbursts. That material is guided by the magnetic field around the star, to the axis of rotation of the magnetic field, which generally lines up with the axis of rotation of the star. Because of the angular momentum of the star, it should maintain that orientation and any new outbursts should go in the same direction as the previous burst.

Re:thanks

[HTH NE1]

Of course when astronomers say it's "about to explode," they really mean it probably exploded 6,500 to 7,500 years ago and we're awaiting the news.

could you clear up that 'sun rise' and 'sun set' thing for me as well?

How about this: even though this expected supernova happened thousands of years ago, for all causal purposes, it won't have any effect upon us until we can see it. After all, the speed of light is really just the speed of causality.

So, in a local causal sense, it hasn't happened yet. The distance just means that if we thought to have any influence on it before it happens here, we'd have to have done something thousands of years ago or longer to exert a causal influence.

Re:Don't hold your breath

[IWannaBeAnAC]

Argh, I was going to moderate this thread, but when I saw this post I felt I should reply instead.

Eta C surely has gone supernova already. General relativity tells us that the passage of time depends on your movements in space, but it doesn't forbit the presence of some 'special' reference frame in which one can consistently give an age on events that happen in the universe. That special reference frame would be the one based on the center of the universe - in effect, the center of mass frame. But even without such a special frame, we can certainly give a precise timeline between any two events no matter how separated they are or how they move. General relativity allows the exact calculation, it just won't be a constant timeline with time moving at the same rate for all observers.

For the case of Eta C, it is located at a distance of 7500 lightyears away, so the light we see from it now left Eta C 7500 years ago. Since we will surely see it go supernova sometime within the next 1000 years, there is no doubt at all that Eta C went supernova sometime between 6500 and 7500 years ago. General relativity doesn't even come into it, it is already clear just from the finite velocity of light.

Re:If we detected it today. . .

[Chris Burke]

You may be thinking of SN 1006, the brightest supernova in recorded history. It was significantly brighter than Venus, though not as bright as the moon. It was bright enough to be easily seen during the day, and was bright enough to read by at night. This event was documented in Chinese, Egyptian, Middle Eastern, Swiss, and even North Americans records, as one would expect of something so amazing. Yet it is conspicuously absent from any other European writings, and the common story (i.e. i can't coroborate at all, may be apocryphal) is that the Church and their "perfect unchanging universe" doctrine made it heresy to even acknowledge that the thing was even there.

Or, maybe you're thinking of SN 1054, which according to Wikipedia may have been described by Irish monastic monks, but was later corrupted into a story of the Antichrist.

Re:Gamma Rays

[The Bad Astronomer]

There are several forces that direct the outflow of an explosion. In this case, it's the rotation of the star coupled with its magnetic fields. When the core collapses, it forms a black hole. The inner parts of the star collapse down too, forming a flattened disk around the BH. The disk rotates quickly, and has ferocious magnetic fields. It's also incredibly hot. This forces material outward, along the poles of the disk. Two beams of energy and matter erupt out, forming what we call a gamma-ray burst. We're pretty sure this will be along the same axis as those two lobes which blew out in the 1800s. So they'll miss us. If the star explodes as a regular old supernova, it's too far away to do any damage; they have to be withing about 100 light years to harm us. I have references for all this, but I won't list them here. I'm writing a chapter in my next book about it... :-)