How much do we know about individual stars in the Andromeda Galaxy? For example, do we know the size of all the ones that can be resolved with telescopes? Or could there be a star in plain view that will turn out to be larger than any star we’ve currently studied? Can the stars in the central bulge be resolved?
Also, what is the furthest galaxy whose individual stars can be resolved from here?
I think that variable stars such as the RR Lyrae (sp?) type are resolved and studied (“resolved” meaning separated from surrounding stars, not visualized as physical disks) in Andromeda and a number of other galaxies. This is a link in the chain of measurements that establishes the scale of the universe.
Stars that become supernovae are individually studied during this process in galaxies that are quite distant. If “resolved” means telescopically identified relative to the things around them, which is a pretty generous definition of the word, then they’d meet that criterion.
Thanks - I knew that supernovae in other galaxies are studied, as well as pulsars and things, but it’s the less unusual stars that I was wondering about, the ones that form the bulk of the spiral arms etc.
I was under the impression that even the nearest stars (in our own galaxy) are so far away that they cannot be resolved (into disks) in telescopes. I could be wrong, (they don’t call me Dufus for nothing) but I think light from other galaxies can’t even be resolved into individual stars.
Perhaps I’m misunderstood the meaning of the word resolved - I knew that even stars in our galaxy are too far away to appear as more than a point of light. What I meant was telling one star from another so that they don’t just merge into a cloud of light.
Well, I stand corrected. It seems individual stars in Andromeda can be resolved:
From this site.
A handful of exceptionally close and/or large stars in our Galaxy can be resolved into disks. I think it is only a literal handful, though, as in less than five. So it’s still a very good general rule to say that they can’t.
Incidentally, the Cepheids, RR Lyraes, etc. that are studied to determine distances to other galaxies are very bright, as stars go. If we had to rely upon main sequence stars like the Sun or Sirius, we wouldn’t have the technology for it.
I didn’t realise that there were any other than Betelgeuse. Just to be clear though, that’s not what I meant when I said “resolved”.
Astronomers speak of “splitting doubles” as a test of a telescope’s ability to resolve close stars as separate points.
There are a fair number of stars that have been “resolved” into disks in the sense of models based on eclipses or rotation and brightness measurements. Whether these count depends on one’s definition of resolution. But there are several stars that have been resolved using telescopic systems that rely on interferometry. Since the different regions of a single telescope objective cooperate through interferometry, I think building a larger telescope by linking smaller ones optically should count in the literal interpretation of “resolve”.
There are examples at http://www.chara.gsu.edu/CHARA/Slides/CHARAoverview.pdf and the ESO web site. On the ESO web site there are a very few pictures of resolved stars, such as one of T Leporis at The star T Leporis as seen with VLTI | ESO. I think these rely on interferometric techniques that are optically resolving the star’s disk.