APOD: A Stellar Jewel Box: Open Cluster... (2019 Oct 13)

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APOD: A Stellar Jewel Box: Open Cluster... (2019 Oct 13)

Post by APOD Robot » Sun Oct 13, 2019 4:08 am

Image A Stellar Jewel Box: Open Cluster NGC 290

Explanation: Jewels don't shine this bright -- only stars do. Like gems in a jewel box, though, the stars of open cluster NGC 290 glitter in a beautiful display of brightness and color. The photogenic cluster, pictured here, was captured in 2006 by the orbiting Hubble Space Telescope. Open clusters of stars are younger, contain few stars, and contain a much higher fraction of blue stars than do globular clusters of stars. NGC 290 lies about 200,000 light-years distant in a neighboring galaxy called the Small Cloud of Magellan (SMC). The open cluster contains hundreds of stars and spans about 65 light years across. NGC 290 and other open clusters are good laboratories for studying how stars of different masses evolve, since all the open cluster's stars were born at about the same time.

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Sam Waldon

Re: APOD: A Stellar Jewel Box: Open Cluster... (2019 Oct 13)

Post by Sam Waldon » Sun Oct 13, 2019 5:03 am

What are the intense red dots in the NGC 290 photo... a special class of stars? There are about 7 or so in this photo.

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Re: APOD: A Stellar Jewel Box: Open Cluster... (2019 Oct 13)

Post by Ann » Sun Oct 13, 2019 5:12 am

Yes, I remember this picture. I didn't like it. You can guess why. The colors seemed strange and, to me, unpleasant. (I know.)

Okay. Let me be a little more productive. How old is this cluster?

NGC 290. NASA, ESA, Hubble; Acknowledgement: E. Olzewski
The Hyades. Photo: Bob King.

























Let's compare NGC 290 with the Hyades. How old is the Hyades? According to Ruth Angus of Astrobites, the Hyades is generally thought to be 625 million years old, but may be as old as 750 or even 950 million years old, if you factor in stellar rotation. Whatever.

As you can see, however, NGC 290 is a totally different sort of cluster than the Hyades. The stars are close together in NGC 290, or at least centrally concentrated, while they are quite far apart in the Hyades. The brightest stars are more or less equally bright in the Hyades, while they come in many different magnitudes in NGC 290. The brightest stars in the Hyades are fairly colorless - the bluest stars are not very blue, and the reddest stars not very red (of course you know that red giant Aldebaran is a foreground star and not a member of the cluster), while in NGC 290 they appear to come in many different colors.

But the colors of the stars in NGC 290 are confusing. There is one bright orange star in NGC 290, but it is located some distance away from the cluster center. Is it even a member of the cluster? There are orange stars well inside the cluster center, but they are clearly fainter than some of the bluer stars. At the same time they are at least moderately bright. This is not what we expect from stellar evolution.

Also the bluest stars seem to be located in the periphery of the cluster. However, there are also orange stars located here. How weird. The brightest stars in the middle are a disgusting turquoise color. (Sorry. Couldn't resist.)

Okay, I'll have a guess as to the age of this cluster. It is clearly younger than the Hyades, if only because the there is such a central concentration of stars in it, and because the stars are of such different brightnesses.

But NGC 290 is also different from the Hyades because it is obviously so very much richer and more massive than the Hyades. So maybe we should compare it with rich open cluster instead of the Hyades, then.

Rich open cluster M11. ESA/Hubble.
Rich open cluster M11. Fort Lewis College - Department of Physics & Engineering.




















According to Wikipedia, the estimated age of M11 is 316±50 million years. As you can see from the picture at right, the bright stars of M11 seem to be of about equal brightness. The cluster, while rich, is not centrally concentrated. (On the other hand, the extremely rich globular cluster Omega Centauri is not centrally concentrated, either.) Although the overall impression of M11 is that it is a bluish cluster, the Hubble closeup of a part of the cluster shows a mixture of blue and orange stars.

The apparent difference in brightness in stars in NGC 290 makes it look younger than M11. M11 is so old that all its truly bright stars have already died. NGC 290 still appears to have some truly bright stars, but probably no true supergiants.

I'll have a guess and say that NGC 290 is about 50-75 million years old.

Ann
Last edited by Ann on Sun Oct 13, 2019 5:19 am, edited 1 time in total.
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Re: APOD: A Stellar Jewel Box: Open Cluster... (2019 Oct 13)

Post by Ann » Sun Oct 13, 2019 5:14 am

Sam Waldon wrote:
Sun Oct 13, 2019 5:03 am
What are the intense red dots in the NGC 290 photo... a special class of stars? There are about 7 or so in this photo.
An interesting possibility is that they might be distant and highly reddened galaxies.

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Re: APOD: A Stellar Jewel Box: Open Cluster... (2019 Oct 13)

Post by neufer » Sun Oct 13, 2019 12:08 pm

Ann wrote:
Sun Oct 13, 2019 5:14 am
Sam Waldon wrote:
Sun Oct 13, 2019 5:03 am

What are the intense red dots in the NGC 290 photo... a special class of stars? There are about 7 or so in this photo.
An interesting possibility is that they might be distant and highly reddened galaxies.
We don't know "what" but we do know "where": http://asterisk.apod.com/viewtopic.php? ... c5#p296102
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Re: APOD: A Stellar Jewel Box: Open Cluster... (2019 Oct 13)

Post by orin stepanek » Sun Oct 13, 2019 12:27 pm

A box full of diamonds and rubies! Oh My! 8-)
Ngc290_HubbleOlszewski_960.jpg
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Re: APOD: A Stellar Jewel Box: Open Cluster... (2019 Oct 13)

Post by BDanielMayfield » Mon Oct 14, 2019 12:25 am

Sam Waldon wrote:
Sun Oct 13, 2019 5:03 am
What are the intense red dots in the NGC 290 photo... a special class of stars? There are about 7 or so in this photo.
Perhaps one or two of the red dots are the redshifted cores of extremely distant galaxies, but there is a more likely explanation: Carbon stars.
A carbon star is typically an asymptotic giant branch star, a luminous red giant, whose atmosphere contains more carbon than oxygen. The two elements combine in the upper layers of the star, forming carbon monoxide, which consumes all the oxygen in the atmosphere, leaving carbon atoms free to form other carbon compounds, giving the star a "sooty" atmosphere and a strikingly ruby red appearance. There are also some dwarf and supergiant carbon stars, with the more common giant stars sometimes being called classical carbon stars to distinguish them.

In most stars (such as the Sun), the atmosphere is richer in oxygen than carbon. Ordinary stars not exhibiting the characteristics of carbon stars but cool enough to form carbon monoxide are therefore called oxygen-rich stars.
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Re: APOD: A Stellar Jewel Box: Open Cluster... (2019 Oct 13)

Post by Ann » Mon Oct 14, 2019 3:29 am

BDanielMayfield wrote:
Mon Oct 14, 2019 12:25 am
Sam Waldon wrote:
Sun Oct 13, 2019 5:03 am
What are the intense red dots in the NGC 290 photo... a special class of stars? There are about 7 or so in this photo.
Perhaps one or two of the red dots are the redshifted cores of extremely distant galaxies, but there is a more likely explanation: Carbon stars.
A carbon star is typically an asymptotic giant branch star, a luminous red giant, whose atmosphere contains more carbon than oxygen. The two elements combine in the upper layers of the star, forming carbon monoxide, which consumes all the oxygen in the atmosphere, leaving carbon atoms free to form other carbon compounds, giving the star a "sooty" atmosphere and a strikingly ruby red appearance. There are also some dwarf and supergiant carbon stars, with the more common giant stars sometimes being called classical carbon stars to distinguish them.

In most stars (such as the Sun), the atmosphere is richer in oxygen than carbon. Ordinary stars not exhibiting the characteristics of carbon stars but cool enough to form carbon monoxide are therefore called oxygen-rich stars.
Carbon star V Aquilae. Gerard Lodriguss/Science Source.



















Well, some of the red objects in the APOD might be carbon stars. There is one relatively faint round red object at far right (at about 2 o'clock) that might be a carbon star. (Or else it might be a dust-reddened star of some kind.) There is another, brighter red star just to the right of the cluster center that might be a carbon star.

I have seen one carbon star through a telescope in my life, V Aquilae. It was an absolutely startling sight.

But take a look at the diffuse red "streaks" at about 11 o'clock in APOD. Move downwards a bit and to the left and you'll find more small red objects. Galaxies tend to clump together, which is why I think that the diffuse red objects at upper left just might be distant galaxies.

NGC 290 detalj.png
Ann
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Aquila [Latin for 'eagle'] represents the bird that carried Jupiter's thunderbolts

Post by neufer » Mon Oct 14, 2019 3:44 pm

Click to play embedded YouTube video.
Ann wrote:
Mon Oct 14, 2019 3:29 am

Well, some of the red objects in the APOD might be carbon stars. There is one relatively faint round red object at far right (at about 2 o'clock) that might be a carbon star. (Or else it might be a dust-reddened star of some kind.) There is another, brighter red star just to the right of the cluster center that might be a carbon star.

I have seen one carbon star through a telescope in my life, V Aquilae. It was an absolutely startling sight.

But take a look at the diffuse red "streaks" at about 11 o'clock in APOD. Move downwards a bit and to the left and you'll find more small red objects. Galaxies tend to clump together, which is why I think that the diffuse red objects at upper left just might be distant galaxies.
Art Neuendorffer

Sam Waldon

Re: APOD: A Stellar Jewel Box: Open Cluster... (2019 Oct 13)

Post by Sam Waldon » Tue Oct 15, 2019 3:18 am

Thanks to all for your responses and suggestions for the intense red colored stars. I learned a lot. Now you've got me intrigued with V Aquilae... guess I'll have to look for it!