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jimnms wrote:Not Found

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jimnms wrote:Not Found

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http://en.wikipedia.org/wiki/Eta_Carinae wrote:
<<Eta Carinae (η Carinae or η Car) is a stellar system in the constellation Carina, about 7,500 to 8,000 light-years from the Sun. The system contains at least two stars, one of which is a luminous blue variable (LBV), which during the early stages of its life had a mass of around 150 solar masses, of which it has lost at least 30 since. It is thought that a hot supergiant of approximately 30 solar masses exists in orbit around its larger companion star, although an enormous thick red nebula surrounding Eta Carinae makes it impossible to see optically.

Eta Carinae is expected to explode as a supernova or hypernova some time within the next million years or so. A supernova or hypernova produced by Eta Carinae would probably eject a gamma ray burst (GRB) out from both polar areas of its rotational axis. Calculations show that the deposited energy of such a GRB striking the Earth's atmosphere would be equivalent to one kiloton of TNT per square kilometer over the entire hemisphere facing the star, with ionizing radiation depositing ten times the lethal whole body dose to the surface. This catastrophic burst would probably not hit Earth, though, because the rotation axis does not currently point towards our solar system. [However,] if Eta Carinae is a binary system, this may affect the future intensity and orientation of the supernova explosion that it produces.

Spectrographic monitoring of Eta Carinae showed that some emission lines faded every 5.52 years, and that this period was stable for decades. The star's radio emission, along with its X-ray brightness, also drop precipitously during these "events" as well. These variations, along with ultra-violet variations, suggest a high probability that Eta Carinae is actually a binary star in which a hot, lower-mass star revolves around η Carinae in a 5.52-year, highly eccentric elliptical orbit. The ionizing radiation emitted by the secondary star in Eta Carinae is the major radiation source of the system. Much of this radiation is absorbed by the primary stellar wind, mainly after it encounters the secondary wind and passes through a shock wave. The amount of absorption depends on the compression factor of the primary wind in the shock wave. The compression factor is limited by the magnetic pressure in the primary wind. The variation of the absorption by the post-shock primary wind with orbital phase changes the ionization structure of the circumbinary gas, and can account for the radio light curve of Eta Carinae. Fast variations near periastron passage are attributed to the onset of the accretion phase.>>

bjmb wrote:let's not forget eta carinae is some 8000 light years away, so we don't know anything about its situation 'now'. all we can sy is that 8000 years ago it has not yet exploded. 'Historical records do show that about 150 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky.' what is meant is 'about 8150 years ago'

MagSec4 wrote:I have a question for anyone with more expertise on the matter:

Everywhere I've read on the subject, it says Eta Carinae is a prime candidate for a supernova soon. Its mass is also reported everywhere as either 100 or 150 solar masses.
Yet the physics of stellar progression expects stars between roughly 8 and 40 or 50 solar masses to undergo a supernova with core collapse; but more massive than that, they are expected to collapse directly into black holes without a supernova.

What part of this conflict is wrong? What am I missing?
Any thoughts?

MagSec4 wrote:
Everywhere I've read on the subject, it says Eta Carinae is a prime candidate for a supernova soon. Its mass is also reported everywhere as either 100 or 150 solar masses.

Yet the physics of stellar progression expects stars between roughly 8 and 40 or 50 solar masses to undergo a supernova with core collapse; but more massive than that, they are expected to collapse directly into black holes without a supernova.

What part of this conflict is wrong? What am I missing?

• Complexity probably.

Boomer12k wrote:Do we call what we are looking at a Planetary Nebula? A PRE-Planetary Nebula? A STELLAR Nebula? Just what do we call this phenomena??? It hasn't exploded yet, is it a NEBULA YET???

Chris Peterson wrote:

bjmb wrote:let's not forget eta carinae is some 8000 light years away, so we don't know anything about its situation 'now'. all we can sy is that 8000 years ago it has not yet exploded. 'Historical records do show that about 150 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky.' what is meant is 'about 8150 years ago'

It does not matter how far away it is. "Now" is almost always defined as the moment of observation. It is quite correct to say that, as of now, this star has not yet produced a supernova. And it is also quite correct to say that it underwent an outburst 150 years ago. You will not find any astronomers saying it happened 8150 years ago, because that number would be inaccurate, would change every time the distance (which is uncertain) is revised, and would have little physical relevance.

FloridaMike wrote:Thank you Chris, Speaking as the Professor of Unnecessary Distinctions, thanks for not adding another....

FloridaMike wrote:

Chris Peterson wrote:

bjmb wrote:let's not forget eta carinae is some 8000 light years away, so we don't know anything about its situation 'now'. all we can sy is that 8000 years ago it has not yet exploded. 'Historical records do show that about 150 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky.' what is meant is 'about 8150 years ago'

It does not matter how far away it is. "Now" is almost always defined as the moment of observation. It is quite correct to say that, as of now, this star has not yet produced a supernova. And it is also quite correct to say that it underwent an outburst 150 years ago. You will not find any astronomers saying it happened 8150 years ago, because that number would be inaccurate, would change every time the distance (which is uncertain) is revised, and would have little physical relevance.

Thank you Chris, Speaking as the Professor of Unnecessary Distinctions, thanks for not adding another....

bjmb wrote:well, has everybody forgotten the 7 minutes of terror? then astronomers were not so bold as to say 'curiosity has now landed' because thet knew they knew (and know) nothing about the 'now' on mars' surface.