Starship Asterisk*

NGC 6357: Cathedral to Massive Stars

Explanation: How massive can a normal star be? Estimates made from distance, brightness and standard solar models had given one star in the open cluster Pismis 24 over 200 times the mass of our Sun, making it one of the most massive stars known. This star is the brightest object located just above the gas front in the featured image. Close inspection of images taken with the Hubble Space Telescope, however, have shown that Pismis 24-1 derives its brilliant luminosity not from a single star but from three at least. Component stars would still remain near 100 solar masses, making them among the more massive stars currently on record. Toward the bottom of the image, stars are still forming in the associated emission nebula NGC 6357. Appearing perhaps like a Gothic cathedral, energetic stars near the center appear to be breaking out and illuminating a spectacular cocoon.

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Looks like a giant alligator snapper from the bayou:
https://i.postimg.cc/s2sPrmk2/image.png

Today's APOD is a fascianting portrait of one of the most remarkable sites of high-mass star formation in our galaxy.

Can't stand the colors, though. There is no way that the star near the bottom of the image, which is deeper embedded in nebulosity that the cluster "above" it, should look bluer than the stars in the upper parts of the image.

No way.

Ann

I really like the photo! I'm going to tip
it on it's side and use it as a wallpaper! A
person could easily have two photos; the
stars on top; or the nebula

Ann wrote: ↑Sun Aug 30, 2020 6:17 am Today's APOD is a fascianting portrait of one of the most remarkable sites of high-mass star formation in our galaxy.

Can't stand the colors, though. There is no way that the star near the bottom of the image, which is deeper embedded in nebulosity that the cluster "above" it, should look bluer than the stars in the upper parts of the image.

No way.

Ann

Ann's comment made me look again, and I note that many stars surrounding the brightest central stars of this cluster have the blue affect, whereas all the central stars are nothing but white.

My initial view of this image was 'oh, that's nice'. But knowing what we've learned about the most massive stars being brilliantly blue, Ann's opinion is well founded.

I'd like to see other views of this scene for scientific comparison. What do the brightest stars here really look like?

Also in the constellation of the Auriga, in the Heart Nebula, in the Northern Cross, in Carina among others there are massive stars

BDanielMayfield wrote: ↑Sun Aug 30, 2020 1:59 pm

Ann wrote: ↑Sun Aug 30, 2020 6:17 am Today's APOD is a fascianting portrait of one of the most remarkable sites of high-mass star formation in our galaxy.

Can't stand the colors, though. There is no way that the star near the bottom of the image, which is deeper embedded in nebulosity that the cluster "above" it, should look bluer than the stars in the upper parts of the image.

No way.

Ann

Ann's comment made me look again, and I note that many stars surrounding the brightest central stars of this cluster have the blue affect, whereas all the central stars are nothing but white.

My initial view of this image was 'oh, that's nice'. But knowing what we've learned about the most massive stars being brilliantly blue, Ann's opinion is well founded.

I'd like to see other views of this scene for scientific comparison. What do the brightest stars here really look like?

Ann's views are mostly spot on; and I'm not smart enough to ? any of them! I wonder about the blue star at the bottom! Does it get some of it's color from all the dust in it's surroundings?

I thought canis majoris was the biggest star in the heavens. I remember on APOD sometime ago, when you started out showing the sun, then went on a movie showing stars as they were bigger, showing stars to scale. pass the ice cold one.

ta152h0 wrote: ↑Sun Aug 30, 2020 9:03 pm I thought canis majoris was the biggest star in the heavens. I remember on APOD sometime ago, when you started out showing the sun, then went on a movie showing stars as they were bigger, showing stars to scale. pass the ice cold one.

Alpha CMa (Sirius) is the brightest star we see in our sky. But it's not very big- about twice the mass of the Sun, and not even twice the diameter. It is bright because of a fairly high intrinsic luminosity, about 25 times that of the Sun, but also because it is one of the closest stars.

ta152h0 wrote: ↑Sun Aug 30, 2020 9:03 pm I thought canis majoris was the biggest star in the heavens. I remember on APOD sometime ago, when you started out showing the sun, then went on a movie showing stars as they were bigger, showing stars to scale. pass the ice cold one.

Cheers!

ta152h0 wrote: ↑Sun Aug 30, 2020 9:03 pm I thought canis majoris was the biggest star in the heavens. I remember on APOD sometime ago, when you started out showing the sun, then went on a movie showing stars as they were bigger, showing stars to scale. pass the ice cold one.

Chris Peterson wrote: ↑Sun Aug 30, 2020 9:41 pm Alpha CMa (Sirius) is the brightest star we see in our sky. But it's not very big- about twice the mass of the Sun, and not even twice the diameter. It is bright because of a fairly high intrinsic luminosity, about 25 times that of the Sun, but also because it is one of the closest stars.

I think he was referring to VY Canis Majoris, but even in the 2018 June 12 APOD UY Scuti has a larger radius, although it is not as massive. For the most massive star (and the most luminous) known star, we look to R136a1 in the LMC, but its radius is only some 30 times that of the Sun.

This just makes me curious. Is Prismis 24-1 real color white or blue? In this APOD they do look white. Yet in this animation from ESA where Prismis 24-1 are actually binary stars, they look incredibly blue. https://www.spacetelescope.org/videos/heic0619b/

fwiw there isn't complete coverage over the entire image with wideband filters to portray accurate star colors relative to one another from the top half to the bottom half. Only the narrowband data cover the whole image. this is just based on me looking at the footprints in the archive search result. I'm not entirely sure how it's composed, but it doesn't look like a complete mosaic to me.

ps that's me trying to say "go easy on whoever made this image they did the best they could with what they had"

geckzilla wrote: ↑Mon Aug 31, 2020 12:54 am ps that's me trying to say "go easy on whoever made this image they did the best they could with what they had"

Roger on that geck. After looking at several of the links in the explanation I noticed that this very same image is featured on NASA webpages. (hey Orin, if you really like it you can buy a poster!) So the work on this image is high quality, even if some artistic license on the star coloring MIGHT have been employed here.

I say that there might have been some creative expertise applied here due to the location of the subject, deep inside the central dust band of the galaxy, near its center where the dust is very thick. Hubble had to peer long and hard to pull data out of this area, I'd guess. So there would have to have been a great deal of signal loss, what astronomers call extinction or interstellar reddening in this image. The producer came up with a picture that looks good, so 'nuf said.