APOD: Doomed Star Eta Carinae (2012 Dec 30)

[APOD Robot]

Doomed Star Eta Carinae

Explanation: Eta Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now. Eta Carinae's mass - about 100 times greater than our Sun - makes it an excellent candidate for a full blown supernova. 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. Eta Carinae, in the Keyhole Nebula, is the only star currently thought to emit natural LASER light. This image, taken in 1996, brought out new details in the unusual nebula that surrounds this rogue star. Now clearly visible are two distinct lobes, a hot central region, and strange radial streaks. The lobes are filled with lanes of gas and dust which absorb the blue and ultraviolet light emitted near the center. The streaks remain unexplained.

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[jimnms]

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The requested URL /apod/image/1212/etacarinae_hst_9000.jpg was not found on this server.

[Ann]

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The requested URL /apod/image/1212/etacarinae_hst_9000.jpg was not found on this server.

To me, all the links worked fine, and I had no trouble finding the APOD itself. But if you can't find it, try a mirror site.

Ann

[Ann]

Eta Carina is perhaps the most remarkable of all stars known to humanity in the Milky Way. The Hubble image is a classic and deserves a repeat. However, some information needs to be updated.

For example, the first Eta Carinae link takes us to a picture of Eta Carinae glowing bright in X-rays. Stars normally don't produce X-rays, not even the very hottest stars. Instead, X-rays usually arise in high-mass binary systems where the strong stellar winds of both stars collide with each other, and many astronomers believe that Eta Carinae is a binary star. This picture shows what the Eta Carinae binary system might look like. The colliding stellar winds form a shock front, seen as a thick white arc in the picture, which wraps around the lower-mass companion. The X-rays come from the shock front.

The star link takes, us, fascinatingly, to a youtube video that zooms in on the Carina Nebula and - on a star that is not Eta Carinae!

The Keyhole nebula link takes us to a mapped color image. The caption tells us that "Sulfur is shown in blue, hydrogen in green and oxygen in red hues". Instead, sulphur is mapped as red and oxygen as blue.

Ann

[bjmb]

Eta Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now.
***
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'

[owlice]

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The requested URL /apod/image/1212/etacarinae_hst_9000.jpg was not found on this server.

Thank you for this; I've notified the editor. It's a typo, I think; the link should be http://apod.nasa.gov/apod/image/1212/et ... st_900.jpg

[metamorphmuses]

I've always loved this image... Eta Carinae looks so menacing... talk about storm clouds brewing!

[orin stepanek]

IMHO; since Eta Carinae spewed out those two lobes; I would think that would extend it's life some! My reasoning is that a lot of pressure would have been alleviated within it's core!

[neufer]

<<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.>>

[Psnarf]

??! WOW!

Ultraviolet laser? What's up with that! http://laserstars.org/news/EtaCarinae.html
Getting a bit rusty in there, what with the double Fe emission lines. Gonna need a lot of WD-40 to fix that.

[MagSec4]

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?

[Tszabeau]

After reading the linked info., I am fuzzy on why Eta Carinae is considered a "rogue star". I thought a rogue was on it's own and not part of a larger system such as galaxy. For example, a rogue planet would not be part of a solar system. I assume that my assumptions must be wrong so what makes it rogue?

[Chris Peterson]

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.

[LSTERNDALE]

Perhaps we should rename this photo as the "Einstein's Brain Nebula"
Sure looks like it!

[metamorphmuses]

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?

When the core collapses at the end of a star's life, it either leaves behind a neutron star, a quark star or a black hole, but that process always* entails a supernova. As far as I know, there is no such thing as core collapse to black hole without a supernova.

* correct me if I'm wrong.

[neufer]

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.

A low metallicity spherically symmetric star of high mass may indeed collapse
directly into a black hole without a supernova (but with a Gamma Ray Burst).

However, Eta Carinae is NOT a low metallicity spherically symmetric star.

Furthermore: Eta Carinae is losing mass at a high rate
(which is interacting with a companion star).

When Eta Carinae dies it will probably be with a bang (or multiple bangs) and not a whimper.

http://en.wikipedia.org/wiki/Hypernova#Collapsar_model

[Boomer12k]

They do "CONE OUT" don't they...Some are seen at different angles so they look circular, but they are actually double cones.

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]

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???

A nebula is simply a concentration of gas and dust, which this is. No explosion is required (although this nebula was actually produced by an explosion). In fact, this is considered an emission nebula, and it has a name- the Homunculus Nebula. It isn't a planetary nebula.

[FloridaMike]

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....

[Chris Peterson]

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

Thank you... I think.

[bjmb]

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....

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. i grant it is irksome we don't know anything with cerainty about the 'now' of the universe, we're always looking at yesteryear and yestermillennium, and always talking about yesterday - still, to date any event by the moment we learn of it is a fallacy, no one says 'tutankhamon was murdered in 1983 because that's when we found out about it'. what's wrong with saying 'we noticed an outburst 150 years ago'? knowing full well that that was not the time it occurred, but only then did we notice it.same for 'we have not yet noticed a supernova explosion at eta carinae'.

[tom2688]

I am always amazed by the images that are submitted here on APOD. due to having three strokes, (one of which has affected my eye sight) I'm unable to view our beautiful galaxy using a telescope so I rely on APOD to show me what I'm missing out on.

That being said I would like to suggest a hypothesis of my own about the "streaks" mentioned in the explanation part of the picture. Seeing that the streaks seem to come from the equatorial region of the star, could they be the result of planets being either fully or partially destroyed, or could they be just shadows of the planets at the time of the stars "outburst"? Of course I'm assuming there are planets around Eta Carinae seeing that there seems to be planets around just about every sun that has been looked at for that reason including binary stars. I thank you in advance for any feedback you may offer.

Respectfully; Tom Dougherty

tom2688@cox.net

[Ann]

A new class of strange stars have been described lately, the supernova impostors. They are much brighter than ordinary novae but fainter than real supernovae. They don't destroy the star having an outburst, but the star loses a lot of mass.

An interesting supernova impostor which turned supernova for real only two years after its impostorous show is Supernova 2009 ip. You can read a discussion thread about it here.

It seems pretty certain that Eta Carina was being a supernova impostor back in 1843, when it underwent a great explosion which wasn't great enough to blow the star to smithereens. Its apparent brightness then rose to -0.8, despite being perhaps 8,000 light-years away. We must also assume that some light from the explosion was lost on its way to the Earth due to dust reddening. Still, those of you who are good at math, if Eta Carina had an apparent brightness of -0.8 in 1843, and we assume it was 8,000 light-years away, and we disregard the question of dust reddening, how bright was it then in absolute terms? What was its absolute visual magnitude?

Ann

[Chris Peterson]

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.

Maintaining a "Martian clock" that was different from an Earth clock makes sense in this case, because we operate in a closed loop: commands are sent to Mars, and responses come back. We have to consider the time of flight of the signal. That is not the case with distant events like supernovas, and that's why astronomers rarely make any effort to consider when something "really" happened, as all that matters is when the observation occurs.

The two exceptions are for the very close (e.g. within our Solar System) and the very far (when we are interested in the state of things during the earlier Universe).

[saturno2]

Distance from Earth to Eta Carinae 7,500 light years.
This is a "short distance" for a explosion of supernova, with a mass 100-120
times the Sun.
Wow!! Eta Carinae emit natural Laser Light