APOD: Doomed Star Eta Carinae (2023 Jul 09)

[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 170 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 featured image brings out details in the unusual nebula that surrounds this rogue star. Diffraction spikes, caused by the telescope, are visible as bright multi-colored streaks emanating from Eta Carinae's center. Two distinct lobes of the Homunculus Nebula encompass the hot central region, while some strange radial streaks are visible in red extending toward the image right. The lobes are filled with lanes of gas and dust which absorb the blue and ultraviolet light emitted near the center. The streaks, however, remain unexplained.

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[Ann]

Doomed Star Eta Carinae. Image Credit & Copyright: NASA, ESA, Hubble; Processing & License: Judy Schmidt

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Wikipedia wrote:

The two main stars of the Eta Carinae system have an eccentric orbit with a period of 5.54 years. The primary is an extremely unusual star, similar to a luminous blue variable (LBV). It was initially 150–250 M☉, of which it has already lost at least 30 M☉, and it is expected to explode as a supernova in the astronomically near future. This is the only star known to produce ultraviolet laser emission. The secondary star is hot and also highly luminous, probably of spectral class O, around 30–80 times as massive as the Sun. The system is heavily obscured by the Homunculus Nebula, which consists of material ejected from the primary during the Great Eruption.

The Great Eruption! It's a good thing our ancestors weren't nearby so that they survived this event!

The illustration below doesn't show Eta Carina, but I like it anyway, and it shows how two massive hot blue stars can produce X-rays when their winds collide:

Artist’s rendering of a colliding wind binary (NASA / C. Reed)

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Impressive, you know! Impressive!

Ann

[AVAO]

Doomed Star Eta Carinae

..."Eta Carinae, in the Keyhole Nebula, is the only star currently thought to emit natural LASER light."...

The word "LASER" is an acronym and stands for "Light Amplification by Stimulated Emission of Radiation". I am not aware of any explanation (cause) for such a mechanism in a star that could explain such an effect?

The passage in the APOD text is only an assumption for which there are scientific references or indications. This should also be presented as such.

Nevertheless a great evergreen by Judy!

[Ann]

Doomed Star Eta Carinae

..."Eta Carinae, in the Keyhole Nebula, is the only star currently thought to emit natural LASER light."...

The word "LASER" is an acronym and stands for "Light Amplification by Stimulated Emission of Radiation". I am not aware of any explanation (cause) for such a mechanism in a star that could explain such an effect?

The passage in the APOD text is only an assumption for which there are scientific references or indications. This should also be presented as such.

Wikipedia wrote:

The ultraviolet spectrum of the Eta Carinae system shows many emission lines of ionised metals such as FeII and CrII, as well as Lymanα (Lyα) and a continuum from a hot central source. The ionisation levels and continuum require the existence of a source with a temperature at least 37,000 K.[58]

Certain FeII UV lines are unusually strong. These originate in the Weigelt Blobs and are caused by a low-gain lasing effect. Ionised hydrogen between a blob and the central star generates intense Lyα emission which penetrates the blob. The blob contains atomic hydrogen with a small admixture of other elements, including iron photo-ionised by radiation from the central stars. An accidental resonance (where emission coincidentally has a suitable energy to pump the excited state) allows the Lyα emission to pump the Fe+ ions to certain pseudo-metastable states,[59] creating a population inversion that allows the stimulated emission to take place.[60] This effect is similar to the maser emission from dense pockets surrounding many cool supergiant stars, but the latter effect is much weaker at optical and UV wavelengths and Eta Carinae is the only clear instance detected of an ultraviolet astrophysical laser. A similar effect from pumping of metastable OI states by Lyβ emission has also been confirmed as an astrophysical UV laser.

I don't understand a word of what Wikipedia is saying about Eta Carina's UV laser, but maybe it makes sense to you?

Ann

[Christian G.]

A "doomed" star is a way to put it, but you could also say a star approaching its apotheosis and grand finale!

[Chris Peterson]

Doomed Star Eta Carinae

..."Eta Carinae, in the Keyhole Nebula, is the only star currently thought to emit natural LASER light."...

The word "LASER" is an acronym and stands for "Light Amplification by Stimulated Emission of Radiation". I am not aware of any explanation (cause) for such a mechanism in a star that could explain such an effect?

The passage in the APOD text is only an assumption for which there are scientific references or indications. This should also be presented as such.

There is abundant observational evidence, and theoretical bases, for the existence of both natural lasers and natural masers.

[orin stepanek]

hard to believe that this star is way bigger than sol's entire solar
system! I sure don't want to go there!

etacarina_chandra.jpg (9.71 KiB) Viewed 1739 times

Eta in X=rays! There was one picture that showed eta in lasers,

Amused dog!

[johnnydeep]

Why is Eta Carinae described as a "rogue" star here? The linked-to study didn't mention it being a rogue star, but I only have access to the abstract. "Rogue" to me means that a star has been ejected from somewhere and is relatively alone. Or is the meaning here only due to Eta Carinae being very unusual?

[Ann]

Why is Eta Carinae described as a "rogue" star here? The linked-to study didn't mention it being a rogue star, but I only have access to the abstract. "Rogue" to me means that a star has been ejected from somewhere and is relatively alone. Or is the meaning here only due to Eta Carinae being very unusual?

"Rogue" in this context can only mean " extremely unusual", because, as you said, Eta Carina has not been ejected from anywhere. And having been ejected is indeed what is usually meant by the expression "rogue star":

Wikipedia wrote:

A rogue star, primarily known as an intergalactic star, is a star that has escaped the gravitational pull of its home galaxy and is moving independently in or towards the intergalactic void. More loosely, any star in an unusual location or state of motion may be termed a rogue star.

A rogue star escaping its home galaxy. Proposed mechanisms for the ejection of intergalactic stars by supermassive black holes. Credit: NASA, ESA, O. Gnedin and W. Brown

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A runaway star that has most likely been kicked out of cluster R136 of the Tarantula Nebula. Credit: NASA, ESA, J. Walsh (ST-ECF). Acknowledgment: Z. Levay (STScI). Credit for ESO image: ESO. Acknowledgments: J. Alves (Calar Alto, Spain), B. Vandame, and Y. Beletski (ESO). Processing by B. Fosbury (ST-ECF).

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Ann

[johnnydeep]

Thanks, Ann.