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.

Re:Gamma Rays

[kungfoofairy]

According to TFA, it's tilted 40 degrees away from us so we won't get hit.

Re:Bad Astronomy?

[spun]

The Bad Astronomy site started out to debunk nutty astronomical theories, like the Electric Universe theory, or the preposterous notion that the moon landing was faked. It's a pretty decent site.

Re:Gamma Rays

[PieSquared]

Stars rotate on an axis. I'm not an astrophysicist, but I'd assume that most of the radiation and gasses would go either in the direction of the axis or in the plane perpendicular to it. I mean, there is a *huge* amount of angular momentum that has to be preserved when you consider mass and the speed of rotation.

So yea, kinda like the death star explosion in the remake. Or maybe perpendicular to that. Once again, not an astrophysicist.

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:I hope no one died.

[spun]

Eta Carinae is so large, it is almost too big to be a star. It has been blowing itself apart every now and then since it was born. I find it unlikely in the extreme that any life could have developed nearby. I doubt the system even has planets.

Re:Gamma Rays

[Intron]

Note that the lobes appear to be tilted away from us by about 40 degrees or so. That's a good thing. When stars like Eta Carinae explode, they tend to shoot of beams of energy and matter that, at its distance of 7500 light years, could kill every living thing on Earth. But since it's pointed away from us, all we'll get is a spectacular light show.

Matter won't get here for quite a while, but the X-Rays, etc. will get here at the same time as the pretty light. For the energy to be enough to kill us at 7500 light years, and the inverse square law to be in effect, that means the energy density at the star's surface would be ... hmmm ... fairly large.

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:Gamma Rays

[secPM_MS]

There is good reason to believe that eta carniae will emit a powerfull gamma ray burst when it collapses. Since the axis of rotation is not pointed anywhere near us, we are at no risk from the gamma beam. It is also possible that it is massive enough to suffer a pair creation supernovae. A recent supernovae of this type in a presumed LBV (luminus blue variable) was ~ 100 X brighter than most core collapse supernovae. Regardless, it is to far away from us to create any type of radiation hazard or even cause problems with perturbing the day - night balance.

Re:If we detected it today. . .

[Chris Burke]

You may be thinking of SN 1006 [wikipedia.org], 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 [wikipedia.org], which according to Wikipedia may have been described by Irish monastic monks, but was later corrupted into a story of the Antichrist.

Re:How fast are the gamma rays moving?

[spun]

Let me introduce you to a thing called the Internet. You can use it to look up facts and dispel ignorance. Well, I can use it that way, anyhow. Evidently you can't. Here you go: http://en.wikipedia.org/wiki/Gamma_radiation [wikipedia.org]

In short, gamma radiation is light. Just very, very high frequency light.

Re:Gamma Rays

[Anonymous Coward]

The inverse square law is always in effect. Lasers dissipate over distance just like sunlight - you can focus a laser down to a tight beam, but it still covers some number of microsteradians of spherical angle. So the area covered will increase as the square of the distance, so the energy per unit area goes as the inverse square.

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... :-)

Re:Eta C is not 7500 light years away for me

[IWannaBeAnAC]

No, even in that case Eta C has already gone supernova. It might only take you one day to get to Eta C in your frame of reference, but in the frame of reference of Eta C (or the frame of reference of the Earth, for that matter) it will take very close to 7,500 years. Since it already went nova at least 6,500 years ago, you will be at least 14,000 years too late if you wanted to see it up close.

Re:Bipolar Symmetric Objects

[The Bad Astronomer]

That's an astute question. Perfect spheres are hard to come by in astronomy, though they're out there (Abell 39 is probably the best example: http://antwrp.gsfc.nasa.gov/apod/image/0101/abell3 9_wiyn_big.jpg [nasa.gov]). The famous Ring Nebula (http://antwrp.gsfc.nasa.gov/apod/ap060625.html) is an object that people thought was a ring, but it turns out to be barrel-shaped and pointed at us. That happened a lot. Bipolar objects are very common, since lots of objects either spin or have disks, which shapes the outflow into two lobes of some kind.

Re:Bad Astronomy?

[Fission86]

This conveniently ignores the fact that Einstein never even mentioned electrodynamics, except in his correspondence with (that expletive) V, and that James Clerk Maxwell demonstrated that e-fields and b-fields are inseparable.

I hate to tell you this dude, but Einstein wrote a little paper called "On the Electodynamics of Moving Bodies" perhaps you've heard of it?

Also, Maxwell never said electric fields and magnetic fields were INSEPERABLE, just that they were connected

Astrophysics continues to be the only field of science where magnetic fields are treated as if they are independent entities that can exist in the absence of electric currents and electric fields.

Also, the reason electric fields can be thought of independantly from magnetic fields, on an astrophysical scale, is that electric fields can extend infinitely from an electric monopole and magnetic fields must return to their source, which i might add has no monopole associated. Pick up an E&M book (i suggest Griffith's, it's pretty good), you might learn what Maxwell's equations actually mean.

People would be wise to consider that it is now an established fact that there exists an interstellar magnetic field whose origin remains unknown.

I'd like to see how you prove that while staying on this planet/in this solar system.

It's interesting that the site is called "Bad Astronomy" -- as if all discussion on that site is meant purely to confirm existing mainstream theories.

Every time someone starts talking about an alternate theory of physics they always have the exact same reaction when people don't believe them "oh, you're a fool for trusting the old ways, blah blah blah." There's a reason these theories are mainstream, they're testable and retestable.

Theories are not evaluated on the basis of their merit alone, but rather how well their creators can withstand a relentless series of withering attacks.

Yes, you are correct, but this is the way of doing things, since nothing can ever be absolutely proven within a finite amount of time (see universe time scale of infinity), a good bet of what is most probable is the best we can ever hope for. And a relentless attack on theories is a good way to do this, if a theory is found lacking, it might be completely wrong or just in need of a tweak. Currently the Standard Model is in one of these categories as it unifies the strong nuclear, weak nuclear and electromagnetic forces, where as gravity is unadressed. And string theory might just be in the other (it's untestable, thus cannot be proven or disproven), but that's another story all-together.

Re:Bad Astronomy?

[RespekMyAthorati]

It's obvious to most of us who made it past grade school that it was a fake.

It's obvious to anyone who actually paid attention in grade school that these "anomalies" have all been explained, although most of them never needed to be. Only an idiot would have any trouble seeing through "anomalies" like "the images are too perfect" (they are far from perfect) or "who took the the picture of Neil Armstrong on the ladder" (the camera was mounted on the lander's base).

Lord, deliver us from morons like you.