by Ann » Fri May 14, 2021 3:15 pm
NCTom wrote: ↑Fri May 14, 2021 2:17 pm
Similar to Orin's question, just how large is the central bulge of this galaxy and is it common for a galaxy to have a star halo around it seemingly twice its diameter?
Also, there is a blue something at the bottom of the photo just right of center, especially clear on the enlargement. Why so blue?
As to why M104 looks the way it does, check out my first
post here. To summarize, M104 is "two galaxies in one", an elliptical galaxy with an accreted ring of stars and dust orbiting around it, not entirely unlike the rings of Saturn.
"The blue something" at bottom right in the APOD looks like just another star, except that it's very blue.
There are a couple of things it could be. It could be a white dwarf, and it could also possibly be a quasar, maybe even a blazar, which is an active galaxy where we look straight into the maw of the jet rushing our way from the supermassive black hole. We should bear in mind that white dwarfs and quasars are likely to be very faint, the white dwarfs because they are intrinsically faint, and the quasars because they are terribly distant. In theory, the blue starlike thing could also be a singularly bright and blue supernova in our own galaxy, but you can bet your boots we would have heard about it if there had been a new supernova in the Milky Way. And we are extremely unlikely to see a supernova in another galaxy in a picture like this, because it would have to be exceedingly faint - bear in mind that we don't even see a host galaxy! Maybe the mystery object could even be a small bright unusually blue planetary nebula.
The most likely object, in my opinion, is a distant unreddened O-type (or even an early B-type) star, particularly one that we see rotating pole on, so that it would it look especially blue from our perspective. If so, it would be a "normal but rare" object in the Milky Way.
Ann
[quote=NCTom post_id=313213 time=1621001834]
Similar to Orin's question, just how large is the central bulge of this galaxy and is it common for a galaxy to have a star halo around it seemingly twice its diameter?
Also, there is a blue something at the bottom of the photo just right of center, especially clear on the enlargement. Why so blue?
[/quote]
As to why M104 looks the way it does, check out my first [url=https://asterisk.apod.com/viewtopic.php?p=313209#p313209]post[/url] here. To summarize, M104 is "two galaxies in one", an elliptical galaxy with an accreted ring of stars and dust orbiting around it, not entirely unlike the rings of Saturn.
"The blue something" at bottom right in the APOD looks like just another star, except that it's very blue.
There are a couple of things it could be. It could be a white dwarf, and it could also possibly be a quasar, maybe even a blazar, which is an active galaxy where we look straight into the maw of the jet rushing our way from the supermassive black hole. We should bear in mind that white dwarfs and quasars are likely to be very faint, the white dwarfs because they are intrinsically faint, and the quasars because they are terribly distant. In theory, the blue starlike thing could also be a singularly bright and blue supernova in our own galaxy, but you can bet your boots we would have heard about it if there had been a new supernova in the Milky Way. And we are extremely unlikely to see a supernova in another galaxy in a picture like this, because it would have to be exceedingly faint - bear in mind that we don't even see a host galaxy! Maybe the mystery object could even be a small bright unusually blue planetary nebula.
The most likely object, in my opinion, is a distant unreddened O-type (or even an early B-type) star, particularly one that we see rotating pole on, so that it would it look especially blue from our perspective. If so, it would be a "normal but rare" object in the Milky Way.
Ann