by Ann » Mon Nov 22, 2010 4:39 pm
I found a Hubble palette image of NGC 6357. Very strange.
Usually I'm quite bored by Hubble palette images, and I will rarely praise them. But they can be useful at times. For example, you can normally expect a nebula to look blue close to an O star if the nebula is shown in the Hubble palette. That is because blue color represents oxygen emission in the Hubble palette, and oxygen emission is usually only present around hot O-type stars. So the blue color of a nebula shown in the Hubble palette tells you that an O star is probably located here.
Well, I found an image of NGC 6357 in the Hubble palette. Guess what? The nebula surrounding the star in today's APOD
is not blue!!! Instead the nebula is yellow from a combination of hydrogen and nitrogen. The hydrogen and nitrogen emission combined with the lack of oxygen strongly suggests to me that the star, impressive-looking as it is, is in fact not an O-type star. Most likely it is an early B-type star instead.
The stars in Pismis 24 are also not surrounded by blue light. My guess is that this cluster has blown away the gas and dust that surrounded it.
But an area of strong nebulosity between Pismis 24 and the star in today's APOD is brightly turquoise, suggesting emission of both oxygen, hydrogen and nitrogen. Also, a "cavity" to the right of Pismis 24, to the right of some dark dusty pillars, is strongly blue! Where does this blue light come from????
Something tells me that I may possibly not be allowed to post the image I found, which is why I did my best to describe it. Here, however, is the image, and let's see how long it lasts:
Ann
I found a Hubble palette image of NGC 6357. Very strange.
Usually I'm quite bored by Hubble palette images, and I will rarely praise them. But they can be useful at times. For example, you can normally expect a nebula to look blue close to an O star if the nebula is shown in the Hubble palette. That is because blue color represents oxygen emission in the Hubble palette, and oxygen emission is usually only present around hot O-type stars. So the blue color of a nebula shown in the Hubble palette tells you that an O star is probably located here.
Well, I found an image of NGC 6357 in the Hubble palette. Guess what? The nebula surrounding the star in today's APOD [i][b]is not blue!!![/b][/i] Instead the nebula is yellow from a combination of hydrogen and nitrogen. The hydrogen and nitrogen emission combined with the lack of oxygen strongly suggests to me that the star, impressive-looking as it is, is in fact not an O-type star. Most likely it is an early B-type star instead.
The stars in Pismis 24 are also not surrounded by blue light. My guess is that this cluster has blown away the gas and dust that surrounded it.
But an area of strong nebulosity between Pismis 24 and the star in today's APOD is brightly turquoise, suggesting emission of both oxygen, hydrogen and nitrogen. Also, a "cavity" to the right of Pismis 24, to the right of some dark dusty pillars, is strongly blue! Where does this blue light come from????
Something tells me that I may possibly not be allowed to post the image I found, which is why I did my best to describe it. Here, however, is the image, and let's see how long it lasts:
[img2]http://2.bp.blogspot.com/_9HcYqbvUc4s/TChFu-RoCQI/AAAAAAAAEl8/QR6AaGUGUXE/s1600/NGC6357HST.jpg[/img2]
Ann