I Which one is Antares in this photo?

[swampwiz]

https://en.wikipedia.org/wiki/Rho_O...le:Antares_and_Rho_Ophiuchi_by_Adam_Block.jpg

The caption says it's the yellow one (false color), but there are 2 such yellow stars, one that is in a clear area, and one that has a cloud around it. Whenever I look (naked-eye) at Antares, I don't see a cloud, but I know that with a low level of resolution, the cloud would not appear to be occluding it.

 

[phyzguy]

This one:

 

[phyzguy]

It's not just the low resolution that keeps your eyes from seeing the cloud. It's that the cloud is much fainter than the star.

 

[russ_watters]

...and no doubt this photo was taken with narrow-band filters that block the vast majority of the light from the stars while letting the light from the nebulae through. So that compresses the dynamic range.

 

[Drakkith]

...and no doubt this photo was taken with narrow-band filters that block the vast majority of the light from the stars while letting the light from the nebulae through. So that compresses the dynamic range.

... AND whoever made the image almost certainly digitally altered the image, bringing out the fainter parts and equalizing things so that the brighter parts of the nebula weren't overexposed at the same time. We do it all the time in astrophotography (for those that don't know).

 

[Ken G]

A fascinating star for those who don't know about it, its mass is about 12 times the Sun's but its radius is some 700 times larger than the Sun's, making it one of the largest stars you can see with the naked eye. This is what it looks like: https://www.space.com/37912-supergiant-star-antares-photos-video.html . That mass means it will eventually go supernova (perhaps pretty soon, actually, maybe even in our lifetime but it's always a long shot), but right now it is puffed out so much because it has some element undergoing fusion in a shell, which means it cannot regulate its fusion temperature the way core fusion can. Hence the fusion is at higher T and going rather nuts, and the only way it can regulate itself is if it lifts off weight. That is the purpose of its huge radius, it reduces the weight of the envelope and stabilizes the shell fusion rate. Since weight goes like mass squared divided by radius squared, the former is some 100 times the Sun, yet the latter is some 500,000 times the Sun, so the weight has been reduced by a factor in the thousands to stabilize its high temperature fusion compared to the core fusion in the Sun.

 

[Ken G]

The effect is similar to the red giants, by the way, it's not just the red supergiants that do this.

 

[snorkack]

If the neutrino detectors detect a powerful, nearby flash say, tonight, do we here on Earth have any clue whether to stare at Betelgeuse or Antares until the shock actually starts breaking out into the bottom of the photosphere?
How long would propagation of the shock take, and who would be notified of a neutrino flash like that?