David Malin once wrote that bubble structures are much less common in the Milky Way than in many smaller galaxies, "because the interstellar material is at the same time both more constrained and more turbulent in our Galaxy, and these delicate structures are swept away before they become recognisable."
So the Milky Way doesn't have the bubbles of dwarf galaxy NGC 6822:
Ah, but we do have a bubble nebula - the Bubble Nebula!
I like Dominic Gareau's image a lot, because it brings out the Bubble Nebula very clearly while at the same time showing us its nebular environment.
The Bubble Nebula is quite distant. Its Gaia parallax puts it at almost 10,000 light-years away. The central star, BD+60 2522 or SAO 20575, is a hot high-mass mass-losing star.
The most typical mass-losing stars are, of course, the Wolf-Rayet stars.The way I understand it - warning! Amateur explanation! - is that the Wolf-Rayet stars may actually still be on the main sequence and fusing hydrogen to helium in their cores, but they are so massive and so hot inside that their nuclear engines run in overdrive, and they generate so much energy that that they simply blow their outer layers away.
More common, I think, are the Wolf-Rayet stars that have left the main sequence, and their already extremely hot cores undergo large changes, which can lead to pretty violent outbursts and mass-loss events.
As for BD+60 2522, Simbad describes it as an O6.5 type star, so it's not a Wolf-Rayet star yet, although it probably will become one. If you are wondering how Simbad can know that BD+60 2522 is not a Wolf-Rayet star, it's because Wolf-Rayet stars have typical WR lines in their spectra, and BD+60 2522 lacks these. Well, a very hot O-type star can have an outburst anyway.
Actually, my guess is that BD+60 2522 has undergone something that is not so much a mass-loss event as an "eruptive event", where the star "sneezed" or "hiccuped" violently and pushed gas away from it in all directions. Or maybe it suffered from temporary indigestion and releasad a sudden gust of wind? Or maybe the star has just systematically, slowly blown almost all surrounding gas away from it, until the gas that was blown away from the star met the surrounding interstellar medium, forming a bubble-like interface.
And bubbles, or rings, appear in unexpected places.
Ann
So the Milky Way doesn't have the bubbles of dwarf galaxy NGC 6822:
Ah, but we do have a bubble nebula - the Bubble Nebula!
I like Dominic Gareau's image a lot, because it brings out the Bubble Nebula very clearly while at the same time showing us its nebular environment.
The Bubble Nebula is quite distant. Its Gaia parallax puts it at almost 10,000 light-years away. The central star, BD+60 2522 or SAO 20575, is a hot high-mass mass-losing star.
The most typical mass-losing stars are, of course, the Wolf-Rayet stars.The way I understand it - warning! Amateur explanation! - is that the Wolf-Rayet stars may actually still be on the main sequence and fusing hydrogen to helium in their cores, but they are so massive and so hot inside that their nuclear engines run in overdrive, and they generate so much energy that that they simply blow their outer layers away.
More common, I think, are the Wolf-Rayet stars that have left the main sequence, and their already extremely hot cores undergo large changes, which can lead to pretty violent outbursts and mass-loss events.
As for BD+60 2522, Simbad describes it as an O6.5 type star, so it's not a Wolf-Rayet star yet, although it probably will become one. If you are wondering how Simbad can know that BD+60 2522 is not a Wolf-Rayet star, it's because Wolf-Rayet stars have typical WR lines in their spectra, and BD+60 2522 lacks these. Well, a very hot O-type star can have an outburst anyway.
Actually, my guess is that BD+60 2522 has undergone something that is not so much a mass-loss event as an "eruptive event", where the star "sneezed" or "hiccuped" violently and pushed gas away from it in all directions. Or maybe it suffered from temporary indigestion and releasad a sudden gust of wind? Or maybe the star has just systematically, slowly blown almost all surrounding gas away from it, until the gas that was blown away from the star met the surrounding interstellar medium, forming a bubble-like interface.
And bubbles, or rings, appear in unexpected places.
Ann
Statistics: Posted by Ann — Wed Oct 30, 2024 7:46 am — Replies 1 — Views 53