Starship Asterisk*

snuggs28 wrote: ↑Fri Mar 29, 2024 3:33 pm I'm mostly passive on this board and just like reading the comments. But I do like my Star clusters.

Wait a minute on this remanent core talk. If it is a dwarf galaxy core. It had to be a real old galaxy. The estimated age of the Omega Centauri stars is from 10-12 billion years old. If that is the case, then this Dwarf Galaxy had to be a first or second-generation galaxy.

For the age of these starts, don't they have to be the most stable stars in the known Universe? Am I wrong in thinking this?

Roy wrote: ↑Thu Mar 28, 2024 10:29 pm M31, Andromeda, has over 500 Global Clusters, GCs. M87, according to a paper by John Huchra of Harvard, has approximately 20,000 GCs. No suggestion of them being leftover cores. I'll stick by my statement that there are too many GCs for them to originate by the stripping method imputed in the original description.

Chris Peterson wrote: ↑Thu Mar 28, 2024 7:43 pm

johnnydeep wrote: ↑Thu Mar 28, 2024 7:24 pm

Chris Peterson wrote: ↑Thu Mar 28, 2024 7:20 pm
I am not. I'm suggesting that "leftover galaxy core" is a lousy term for it, and that it isn't even a globular cluster, except visually. My point is that there's no evidence that globular clusters (plural, in general) are "leftover galaxy cores".

Ok, but it seems the paper is arguing (or might be - I don't have full access) that it is indeed a "remnant galaxy core", which I take to be the same as a "left over galaxy core".

I don't think the two terms are really synonymous. But in any case, the important point is that this singular object is very different from other bodies we call "globular clusters".

Roy wrote: ↑Thu Mar 28, 2024 8:38 pm Some astronomers think there is a black hole in omega Centauri. Five others think that if that is so, it could be the center of a small galaxy stripped of its peripheral stars. They look in that area of the sky, and find 309 stars that seem to be of the same age as omega Centauri, in an arc pointed at the cluster. They name it "Fimbulthul". Lots of "what ifs" and conjecture and data selection in that logic sequence. Can it be falsified?
My original remark about "leftover" galaxy cores referred to a galaxy being stripped of all except the central core stars after it had passed through the large galaxy, on the way to becoming an orbiting globular cluster - that there were too many globular clusters for that process to be the source of them.
In this case remnant and leftover are substantially the same semantics.

johnnydeep wrote: ↑Thu Mar 28, 2024 7:24 pm

Chris Peterson wrote: ↑Thu Mar 28, 2024 7:20 pm

johnnydeep wrote: ↑Thu Mar 28, 2024 6:56 pm

Well, doesn't it say that Omega Centauri is - or very well could be - the remnant core of a cannibalized galaxy? And aren't you arguing that it's not?

I am not. I'm suggesting that "leftover galaxy core" is a lousy term for it, and that it isn't even a globular cluster, except visually. My point is that there's no evidence that globular clusters (plural, in general) are "leftover galaxy cores".

Ok, but it seems the paper is arguing (or might be - I don't have full access) that it is indeed a "remnant galaxy core", which I take to be the same as a "left over galaxy core".

Chris Peterson wrote: ↑Thu Mar 28, 2024 7:20 pm

johnnydeep wrote: ↑Thu Mar 28, 2024 6:56 pm

Chris Peterson wrote: ↑Thu Mar 28, 2024 6:46 pm
What of it?

Well, doesn't it say that Omega Centauri is - or very well could be - the remnant core of a cannibalized galaxy? And aren't you arguing that it's not?

I am not. I'm suggesting that "leftover galaxy core" is a lousy term for it, and that it isn't even a globular cluster, except visually. My point is that there's no evidence that globular clusters (plural, in general) are "leftover galaxy cores".

johnnydeep wrote: ↑Thu Mar 28, 2024 6:56 pm

Chris Peterson wrote: ↑Thu Mar 28, 2024 6:46 pm

johnnydeep wrote: ↑Thu Mar 28, 2024 6:42 pm

What of this paper then - https://www.nature.com/articles/s41550-019-0751-x

What of it?

Well, doesn't it say that Omega Centauri is - or very well could be - the remnant core of a cannibalized galaxy? And aren't you arguing that it's not?

Chris Peterson wrote: ↑Thu Mar 28, 2024 6:46 pm

johnnydeep wrote: ↑Thu Mar 28, 2024 6:42 pm

Chris Peterson wrote: ↑Thu Mar 28, 2024 6:03 pm

I would not characterize the remnant of a collision as a "leftover galaxy core"! In any case, the hypothesis that Omega Centauri isn't a "true" globular cluster, but rather something left from a collision, is based on the observation that its stellar population looks very different from that of other globular clusters... the overwhelming majority of which present stellar populations that look nothing like galaxy cores.

What of this paper then - https://www.nature.com/articles/s41550-019-0751-x

Abstract
Omega Centauri (ω Cen) is the Milky Way’s most massive globular cluster, and has long been suspected of being the remnant core of an accreted dwarf galaxy. If this scenario is correct, ω Cen should be tidally limited and tidal debris should be spread along its orbit. Here we use N-body simulations to show that the recently discovered ‘Fimbulthul’ structure is the long-sought-for tidal stream of ω Cen, extending up to 28° from the cluster. Follow-up high-resolution spectroscopy of five stream stars shows that they are closely grouped in velocity, and have metallicities consistent with having originated in that cluster. Informed by our N-body simulations, we devise a selection filter that we apply to Gaia mission data to also uncover the stream in the highly contaminated and crowded field within 10° of ω Cen. Further modelling of the stream may help to constrain the dynamical history of the dwarf galaxy progenitor of this disrupting system and guide future searches for its remnant stars in the Milky Way.

What of it?

johnnydeep wrote: ↑Thu Mar 28, 2024 6:42 pm

Chris Peterson wrote: ↑Thu Mar 28, 2024 6:03 pm

Ann wrote: ↑Thu Mar 28, 2024 5:57 pm

I take it that there is some evidence that Omega Centauri is?

Ann

I would not characterize the remnant of a collision as a "leftover galaxy core"! In any case, the hypothesis that Omega Centauri isn't a "true" globular cluster, but rather something left from a collision, is based on the observation that its stellar population looks very different from that of other globular clusters... the overwhelming majority of which present stellar populations that look nothing like galaxy cores.

What of this paper then - https://www.nature.com/articles/s41550-019-0751-x

Abstract
Omega Centauri (ω Cen) is the Milky Way’s most massive globular cluster, and has long been suspected of being the remnant core of an accreted dwarf galaxy. If this scenario is correct, ω Cen should be tidally limited and tidal debris should be spread along its orbit. Here we use N-body simulations to show that the recently discovered ‘Fimbulthul’ structure is the long-sought-for tidal stream of ω Cen, extending up to 28° from the cluster. Follow-up high-resolution spectroscopy of five stream stars shows that they are closely grouped in velocity, and have metallicities consistent with having originated in that cluster. Informed by our N-body simulations, we devise a selection filter that we apply to Gaia mission data to also uncover the stream in the highly contaminated and crowded field within 10° of ω Cen. Further modelling of the stream may help to constrain the dynamical history of the dwarf galaxy progenitor of this disrupting system and guide future searches for its remnant stars in the Milky Way.

Chris Peterson wrote: ↑Thu Mar 28, 2024 6:03 pm

Ann wrote: ↑Thu Mar 28, 2024 5:57 pm

Chris Peterson wrote: ↑Thu Mar 28, 2024 1:59 pm

There is no evidence that globular clusters are "leftover galaxy cores".

I take it that there is some evidence that Omega Centauri is?

Ann

I would not characterize the remnant of a collision as a "leftover galaxy core"! In any case, the hypothesis that Omega Centauri isn't a "true" globular cluster, but rather something left from a collision, is based on the observation that its stellar population looks very different from that of other globular clusters... the overwhelming majority of which present stellar populations that look nothing like galaxy cores.

Abstract
Omega Centauri (ω Cen) is the Milky Way’s most massive globular cluster, and has long been suspected of being the remnant core of an accreted dwarf galaxy. If this scenario is correct, ω Cen should be tidally limited and tidal debris should be spread along its orbit. Here we use N-body simulations to show that the recently discovered ‘Fimbulthul’ structure is the long-sought-for tidal stream of ω Cen, extending up to 28° from the cluster. Follow-up high-resolution spectroscopy of five stream stars shows that they are closely grouped in velocity, and have metallicities consistent with having originated in that cluster. Informed by our N-body simulations, we devise a selection filter that we apply to Gaia mission data to also uncover the stream in the highly contaminated and crowded field within 10° of ω Cen. Further modelling of the stream may help to constrain the dynamical history of the dwarf galaxy progenitor of this disrupting system and guide future searches for its remnant stars in the Milky Way.

Ann wrote: ↑Thu Mar 28, 2024 5:57 pm

Chris Peterson wrote: ↑Thu Mar 28, 2024 1:59 pm

Roy wrote: ↑Thu Mar 28, 2024 1:47 pm Globular clusters are leftover galaxy cores? The 2010 count of them was 157. We see large numbers of them in the Andromeda galaxy, and other galaxies. So, based on that number crunching, clusters are two or three orders of magnitude more common than galaxies.

There is no evidence that globular clusters are "leftover galaxy cores".

I take it that there is some evidence that Omega Centauri is?

Ann

Chris Peterson wrote: ↑Thu Mar 28, 2024 1:59 pm

Roy wrote: ↑Thu Mar 28, 2024 1:47 pm Globular clusters are leftover galaxy cores? The 2010 count of them was 157. We see large numbers of them in the Andromeda galaxy, and other galaxies. So, based on that number crunching, clusters are two or three orders of magnitude more common than galaxies.

There is no evidence that globular clusters are "leftover galaxy cores".

zendae wrote: ↑Thu Mar 28, 2024 2:37 pm I've asked this before re the Hercules cluster: do astronomers know the approximate distance between the closest stars to each other here? They seem to know the approximate number of stars, and the size and distance of the structure. I'm assuming things are not homogeneous tho: some stars are relatively closer to each other than others.
It certainly is a good representation of how close stars appear to be to each other from our visual perspective, yet how far they actually are from each other, and both how great and miniscule the span of distance a light year is.

If we were viewing from the center of this, I do wonder what the "sky" would look like compared to ours.

Wikipedia wrote:
The stars in the core of Omega Centauri are so crowded that they are estimated to average only 0.1 light-year away from each other.

zendae wrote: ↑Thu Mar 28, 2024 2:37 pm I've asked this before re the Hercules cluster: do astronomers know the approximate distance between the closest stars to each other here? They seem to know the approximate number of stars, and the size and distance of the structure. I'm assuming things are not homogeneous tho: some stars are relatively closer to each other than others.
It certainly is a good representation of how close stars appear to be to each other from our visual perspective, yet how far they actually are from each other, and both how great and miniscule the span of distance a light year is.

If we were viewing from the center of this, I do wonder what the "sky" would look like compared to ours.

Roy wrote: ↑Thu Mar 28, 2024 1:47 pm Globular clusters are leftover galaxy cores? The 2010 count of them was 157. We see large numbers of them in the Andromeda galaxy, and other galaxies. So, based on that number crunching, clusters are two or three orders of magnitude more common than galaxies.

smitty wrote: ↑Thu Mar 28, 2024 1:08 pm Is gravitational attraction causing the stars to move toward the center of the cluster? If not, why not?