Starship Asterisk*

neufer wrote: ↑Thu Aug 06, 2020 8:07 pm

johnnydeep wrote: ↑Thu Aug 06, 2020 7:13 pm

orin stepanek wrote: ↑Thu Aug 06, 2020 6:21 pm
Isn't Methuselah A supermassive star? And yet it is very old! https://video.search.yahoo.com/yhs/sear ... tion=click

Wikipedia says it's only .8 times the mass of the sun, with twice the radius and 5 times the luminosity. See https://en.wikipedia.org/wiki/HD_140283

The sun will be come a red giant in about 5 billion years, at which point it will be 9.5 billion years old. The Methuselah star is estimated to be about 13.5 billion years old, but is not a red giant...(yet?).

lower-mass tracks show very short long-lasting subgiant branches

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Methuselah was (for a long time) a low mass low luminosity star that is so old that it has recently left the main sequence and become relatively large bright subgiant star.

Methuselah star age: 13.66-15.26 Gyrs.
Planck Universe age: 13.78-14.02 Gyrs.

(Close enough for government work.)

Since Methuselah is suffering from iron-deficiency anemia it is unfortunate that a radial velocity of −169 km/s indicates that it is not willing to stay socially distanced (at 202.4 ly).

johnnydeep wrote: ↑Thu Aug 06, 2020 7:13 pm

orin stepanek wrote: ↑Thu Aug 06, 2020 6:21 pm
Isn't Methuselah A supermassive star? Andyet it is very old! https://video.search.yahoo.com/yhs/sear ... tion=click

Wikipedia says it's only .8 times the mass of the sun, with twice the radius and 5 times the luminosity. See https://en.wikipedia.org/wiki/HD_140283

The sun will be come a red giant in about 5 billion years, at which point it will be 9.5 billion years old. The Methuselah star is estimated to be about 13.5 billion years old, but is not a red giant...(yet?). Not sure if that makes total sense to me, but here is some more from that Wikipedia page:

Because HD 140283 is neither on the main sequence nor a red giant, its early position in the Hertzsprung-Russell diagram has been interpreted with its data and theoretical models of stellar evolution based on quantum mechanics and the observations of processes in millions of stars to infer its old age. For field stars (as opposed to stars in clusters) it is rare to know a star's luminosity, surface temperature and composition precisely enough to get a well-constrained value for their age; because of their relative scarcity, this is even rarer for a Population II star like HD 140283. A study published in 2013[13][14] used the Fine Guidance Sensors of NASA's Hubble Space Telescope to measure a precise parallax (and therefore distance and luminosity) for the star,[1] and employ this information to estimate an age for the star of 14.46 ± 0.8 billion years.[1] Due to the uncertainty in the value, this age for the star may or may not conflict with the calculated age of the Universe as determined by the final 2015 Planck satellite results of 13.799 ± 0.021 billion years.[1][15]

Once dubbed the "Methuselah Star" by the popular press due to its age, if the assumptions of stellar evolution are correct in the report, the star must have formed soon after the Big Bang[1] and is one of the oldest stars known.[citation needed] The search for such very iron-poor stars has shown they are almost all anomalies in globular clusters and the Galactic Halo. This concords with a narrative that they are rare survivors of their generation.

johnnydeep wrote: ↑Thu Aug 06, 2020 7:13 pm

orin stepanek wrote: ↑Thu Aug 06, 2020 6:21 pm
Isn't Methuselah A supermassive star? And yet it is very old! https://video.search.yahoo.com/yhs/sear ... tion=click

Wikipedia says it's only .8 times the mass of the sun, with twice the radius and 5 times the luminosity. See https://en.wikipedia.org/wiki/HD_140283

The sun will be come a red giant in about 5 billion years, at which point it will be 9.5 billion years old. The Methuselah star is estimated to be about 13.5 billion years old, but is not a red giant...(yet?).

orin stepanek wrote: ↑Thu Aug 06, 2020 6:21 pm
Isn't Methuselah A supermassive star? Andyet it is very old! https://video.search.yahoo.com/yhs/sear ... tion=click

Because HD 140283 is neither on the main sequence nor a red giant, its early position in the Hertzsprung-Russell diagram has been interpreted with its data and theoretical models of stellar evolution based on quantum mechanics and the observations of processes in millions of stars to infer its old age. For field stars (as opposed to stars in clusters) it is rare to know a star's luminosity, surface temperature and composition precisely enough to get a well-constrained value for their age; because of their relative scarcity, this is even rarer for a Population II star like HD 140283. A study published in 2013[13][14] used the Fine Guidance Sensors of NASA's Hubble Space Telescope to measure a precise parallax (and therefore distance and luminosity) for the star,[1] and employ this information to estimate an age for the star of 14.46 ± 0.8 billion years.[1] Due to the uncertainty in the value, this age for the star may or may not conflict with the calculated age of the Universe as determined by the final 2015 Planck satellite results of 13.799 ± 0.021 billion years.[1][15]

Once dubbed the "Methuselah Star" by the popular press due to its age, if the assumptions of stellar evolution are correct in the report, the star must have formed soon after the Big Bang[1] and is one of the oldest stars known.[citation needed] The search for such very iron-poor stars has shown they are almost all anomalies in globular clusters and the Galactic Halo. This concords with a narrative that they are rare survivors of their generation.

neufer wrote: ↑Thu Aug 06, 2020 3:20 pm

Ann wrote: ↑Thu Aug 06, 2020 2:01 pm

orin stepanek wrote: ↑Thu Aug 06, 2020 11:44 am
I know that the sun is supposed to be middle aged at about 4 1/2 to 5 billion years in age! It is supposedly called a 3rd generation star! I guess that means it was made up from the leftovers of preceding stars! So I'm Thinking 8 million years makes them pretty young! Maybe not?

Yes, 8 million years is certainly young for stars!

I was just making the point that all massive stars are young, because they don't live to be old.

But you are right, M21 is a young cluster!

https://en.wikipedia.org/wiki/Open_cluster wrote:

At 8 million years M21 is just a toddler in many respects.

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<<An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist. They are loosely bound by mutual gravitational attraction and become disrupted by close encounters with other clusters and clouds of gas as they orbit the galactic center. This can result in a migration to the main body of the galaxy and a loss of cluster members through internal close encounters. Open clusters generally survive for a few hundred million years, with the most massive ones surviving for a few billion years.

Young open clusters may be contained within the molecular cloud from which they formed, illuminating it to create an H II region. Over time, radiation pressure from the cluster will disperse the molecular cloud. Typically, about 10% of the mass of a gas cloud will coalesce into stars before radiation pressure drives the rest of the gas away.

Open clusters are key objects in the study of stellar evolution. Because the cluster members are of similar age and chemical composition, their properties (such as distance, age, metallicity, extinction, and velocity) are more easily determined than they are for isolated stars. A number of open clusters, such as the Pleiades, Hyades or the Alpha Persei Cluster are visible with the naked eye.>>

Ann wrote: ↑Thu Aug 06, 2020 2:01 pm

orin stepanek wrote: ↑Thu Aug 06, 2020 11:44 am
I know that the sun is supposed to be middle aged at about 4 1/2 to 5 billion years in age! It is supposedly called a 3rd generation star! I guess that means it was made up from the leftovers of preceding stars! So I'm Thinking 8 million years makes them pretty young! Maybe not?

Yes, 8 million years is certainly young for stars! I was just making the point that all massive stars are young, because they don't live to be old.

But you are right, M21 is a young cluster!

Ann

neufer wrote: ↑Thu Aug 06, 2020 3:20 pm

Ann wrote: ↑Thu Aug 06, 2020 2:01 pm

orin stepanek wrote: ↑Thu Aug 06, 2020 11:44 am
I know that the sun is supposed to be middle aged at about 4 1/2 to 5 billion years in age! It is supposedly called a 3rd generation star! I guess that means it was made up from the leftovers of preceding stars! So I'm Thinking 8 million years makes them pretty young! Maybe not?

Yes, 8 million years is certainly young for stars!

I was just making the point that all massive stars are young, because they don't live to be old.

But you are right, M21 is a young cluster!

https://en.wikipedia.org/wiki/Open_cluster wrote:

At 8 million years M21 is just a toddler in many respects.

---

<<An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist. They are loosely bound by mutual gravitational attraction and become disrupted by close encounters with other clusters and clouds of gas as they orbit the galactic center. This can result in a migration to the main body of the galaxy and a loss of cluster members through internal close encounters. Open clusters generally survive for a few hundred million years, with the most massive ones surviving for a few billion years.

Ann wrote: ↑Thu Aug 06, 2020 2:01 pm

orin stepanek wrote: ↑Thu Aug 06, 2020 11:44 am
I know that the sun is supposed to be middle aged at about 4 1/2 to 5 billion years in age! It is supposedly called a 3rd generation star! I guess that means it was made up from the leftovers of preceding stars! So I'm Thinking 8 million years makes them pretty young! Maybe not?

Yes, 8 million years is certainly young for stars!

I was just making the point that all massive stars are young, because they don't live to be old.

But you are right, M21 is a young cluster!

https://en.wikipedia.org/wiki/Open_cluster wrote:

At 8 million years M21 is just a toddler in many respects.

---

<<An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist. They are loosely bound by mutual gravitational attraction and become disrupted by close encounters with other clusters and clouds of gas as they orbit the galactic center. This can result in a migration to the main body of the galaxy and a loss of cluster members through internal close encounters. Open clusters generally survive for a few hundred million years, with the most massive ones surviving for a few billion years.

Young open clusters may be contained within the molecular cloud from which they formed, illuminating it to create an H II region. Over time, radiation pressure from the cluster will disperse the molecular cloud. Typically, about 10% of the mass of a gas cloud will coalesce into stars before radiation pressure drives the rest of the gas away.

Open clusters are key objects in the study of stellar evolution. Because the cluster members are of similar age and chemical composition, their properties (such as distance, age, metallicity, extinction, and velocity) are more easily determined than they are for isolated stars. A number of open clusters, such as the Pleiades, Hyades or the Alpha Persei Cluster are visible with the naked eye.>>

orin stepanek wrote: ↑Thu Aug 06, 2020 11:44 am
I know that the sun is supposed to be middle aged at about 4 1/2 to 5 billion years in age! It is supposedly called a 3rd generation star! I guess that means it was made up from the leftovers of preceding stars! So I'm Thinking 8 million years makes them pretty young! Maybe not?

http://www.messier.seds.org/m/m020.html wrote:
<<The [Trifid] nebula's distance is rather uncertain, with values between 2,200 light years (Mallas/Kreimer; Glyn Jones has 2,300) and about 7,600 light years (C.R. O'Dell 1963). The Sky Catalog 2000 gives 5,200 light years, a value which is also used by Archinal and Hynes (2003), and which we adopt here. The WEBDA database has 3140, the Hubble Press Release of Jeff Hester (STScI-PRC99-42) gives "about 9000" light years.>>

https://en.wikipedia.org/wiki/Trifid_Nebula wrote:

The [Trifid] nebula's distance: 4100 ± 200 ly

https://arxiv.org/abs/1807.02115 wrote:

Kinematics in Young Star Clusters and Associations with Gaia DR2

Michael A. Kuhn (1), Lynne A. Hillenbrand (1), Alison Sills (2), Eric D. Feigelson (3), Konstantin V. Getman (3) ((1) California Institute of Technology, (2) McMaster University, (3) Pennsylvania State University)

Submitted on 5 Jul 2018

<<The Gaia mission has opened a new window into the internal kinematics of young star clusters at the sub-km/s level, with implications for our understanding of how star clusters form and evolve. We use a sample of 28 clusters and associations with ages from 1-5 Myr, where lists of members are available from previous X-ray, optical, and infrared studies. Proper motions from Gaia DR2 reveals that at least 75% of these systems are expanding; however, rotation is only detected in one system. Typical expansion velocities are on the order of ~0.5 km/s, and, in several systems, there is a positive radial gradient in expansion velocity. Systems that are still embedded in molecular clouds are less likely to be expanding than those that are partially or fully revealed. One-dimensional velocity dispersions, which range from 1 to 3 km/s, imply that most of the stellar systems in our sample are supervirial and that some are unbound. In star-forming regions that contain multiple clusters or subclusters, we find no evidence that these groups are coalescing, implying that hierarchical cluster assembly, if it occurs, must happen rapidly during the embedded stage.>>

Ann wrote: ↑Thu Aug 06, 2020 11:16 am

orin stepanek wrote: ↑Thu Aug 06, 2020 10:46 am

APOD Robot wrote: ↑Thu Aug 06, 2020 4:06 am Messier 20 and 21
Trisected by dust lanes the Trifid itself is about 40 light-years across and a mere 300,000 years old. That makes it one of the youngest star forming regions in our sky, with newborn and embryonic stars embedded in its natal dust and gas clouds. Estimates of the distance to open star cluster M21 are similar to M20's, but though they share this gorgeous telescopic skyscape there is no apparent connection between the two. In fact, M21's stars are much older, about 8 million years old.

trifidnebulaM20M21_1024.jpg


Actually; isn't 8 million years quite young for stars; even
though they are a lot older than the 300,000 years for trifid?

The Pleiades, a young cluster at a 100 million years old. Photo: Marco Lorenzi.

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Absolutely, yes, it is! Consider the Pleiades! They are around 100 million years old, and they are considered young!

But it's all a matter of mass, as you know. The more massive a star is, the shorter is its lifetime. The mass of stars of the Pleiades is only a few times that of the Sun (the brightest member of the Pleiades, Alcyone, has a mass of 6 solar, according to Jim Kaler).

The brightest members of M21 are certainly more massive. But how massive? I'm not sure if the nature of the stars in M21 is really known. My guess is that the brightest member of M21, HD 164863, has a mass of at least 12 times that of the Sun, maybe more. And if so, an age of 8 million years is not that young.

Why did I say that the brightest member of M21 is about 12 times as massive as the Sun? Well, I'm totally guessing. But Jim Kaler has said that Betelgeuse, which as we all know is an extremely evolved supergiant star, probably started out with a mass 18-19 times solar.

And according to Wikipedia, Betelgeuse is probably about the same age as the stars of M21, some 8 million years. So if Betelgeuse and the stars of M21 are contemporaries, we should assume that Betelgeuse started out more massive than any of the stars in M21, since it is so much more highly evolved.

The stars of M21 are "unevolved", at least in the respect that they are still blue. No red giants can be seen in the cluster. This, interestingly, is an aspect they have in common with the Pleiades. But the Pleiades is suspected to have had at least one red giant in the past, because this cluster does seem contain a white dwarf, named EG 25 (LB 1497).

Ann

orin stepanek wrote: ↑Thu Aug 06, 2020 10:46 am

APOD Robot wrote: ↑Thu Aug 06, 2020 4:06 am Messier 20 and 21
Trisected by dust lanes the Trifid itself is about 40 light-years across and a mere 300,000 years old. That makes it one of the youngest star forming regions in our sky, with newborn and embryonic stars embedded in its natal dust and gas clouds. Estimates of the distance to open star cluster M21 are similar to M20's, but though they share this gorgeous telescopic skyscape there is no apparent connection between the two. In fact, M21's stars are much older, about 8 million years old.

trifidnebulaM20M21_1024.jpg


Actually; isn't 8 million years quite young for stars; even
though they are a lot older than the 300,000 years for trifid?

APOD Robot wrote: ↑Thu Aug 06, 2020 4:06 am Messier 20 and 21
Trisected by dust lanes the Trifid itself is about 40 light-years across and a mere 300,000 years old. That makes it one of the youngest star forming regions in our sky, with newborn and embryonic stars embedded in its natal dust and gas clouds. Estimates of the distance to open star cluster M21 are similar to M20's, but though they share this gorgeous telescopic skyscape there is no apparent connection between the two. In fact, M21's stars are much older, about 8 million years old.

APOD Robot wrote:

Trisected by dust lanes the Trifid itself is about 40 light-years across and a mere 300,000 years old.