APOD: NGC 4755: A Jewel Box of Stars (2010 Aug 17)

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APOD: NGC 4755: A Jewel Box of Stars (2010 Aug 17)

Post by APOD Robot » Tue Aug 17, 2010 5:11 am

Image NGC 4755: A Jewel Box of Stars

Explanation: The great variety of star colors in this open cluster underlies its name: The Jewel Box. One of the bright central stars is a red supergiant, in contrast to the many blue stars that surround it. The cluster, also known as Kappa Crucis contains just over 100 stars, and is about 10 million years old. Open clusters are younger, contain few stars, and contain a much higher fraction of blue stars than do globular clusters. This Jewel Box lies about 6,400 light-years away, so the light that we see today was emitted from the cluster before even the Great Pyramids in Egypt were built. The Jewel Box, pictured above, spans about 20 light-years, and can be seen with binoculars towards the southern constellation of the cross (Crux).

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Re: APOD: NGC 4755: A Jewel Box of Stars (2010 Aug 17)

Post by bystander » Tue Aug 17, 2010 6:34 am

First seen on the Observation Deck, here.

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Re: APOD: NGC 4755: A Jewel Box of Stars (2010 Aug 17)

Post by orin stepanek » Tue Aug 17, 2010 12:00 pm

How did the red giant happen to be among the young blue stars? I'm wondering if maybe it was the cause of star forming in a region of ripe stellar dust?
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Re: APOD: NGC 4755: A Jewel Box of Stars (2010 Aug 17)

Post by terrastro » Tue Aug 17, 2010 12:20 pm

orin stepanek wrote:How did the red giant happen to be among the young blue stars? I'm wondering if maybe it was the cause of star forming in a region of ripe stellar dust?
I had the same question a while back and found this:
Larger stars have more fuel, but they have to burn (fuse) it faster in order to maintain equilibrium. Because thermonuclear fusion occurs at a faster rate in massive stars, large stars use all of their fuel in a shorter length of time.
http://aspire.cosmic-ray.org/labs/star_ ... uence.html

So the large stars just age quicker.

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Re: APOD: NGC 4755: A Jewel Box of Stars (2010 Aug 17)

Post by León » Tue Aug 17, 2010 12:57 pm

Transcribe
1. the stars in a cluster are all at about the same distance
2. the stars have approximately the same age
3. the stars have about the same chemical composition
4. the stars have different masses, ranging from about 80-100 solar masses for the most massive stars in very young clusters to less than about 0.08 solar masses. http://www.seds.org/messier/open.html

This cluster is one of the youngest known, with an estimated age of only 7.1 million years (Sky Catalog 2000). Its hottest star is of spectral type B0. According to Burnham, the 3 brightest stars are blue giants of mag 5.75 and spectral type B9, mag 5.94 and type B3, and mag 6.80/B2, while the fourth brightest star is a mag 7.58 M2 red supergiant. Another mag 5.7/spectral type A1 star is probably also a member, another white supergiant: This star would be the brioghtest of the cluster at about absolute magnitude -7.7 (83,000 solar luminosities).

As I am of the view that planets are remnants of stars, I would emphasize in Section 4. For now, comes up as, the studies are made from the most notable stars that are larger, but in the neighborhood and especially within the solar system to focus the studies require small stars.

Regarding the cluster, it is conceivable that the central star and old giant orange, like Betelgeuse, it could be the mother of the cluster to be ionized nebula of the raw material
supplier.
Down the globular cluster NGC 1818 ought to be called jewelry by color
Image

thoughtfool

Re: APOD: NGC 4755: A Jewel Box of Stars (2010 Aug 17)

Post by thoughtfool » Tue Aug 17, 2010 1:36 pm

I have always wondered whether it would be possible in some way to "code" the light emitted from an object or if we can find some code in light emitted by an object. In this example, if we could try and find some useful information from the light emitted by these stars, we may know what it was like 6400 years ago in that star (or universe). Are there any studies being done relating to this? I am asking about information that we can possibly send/ receive that goes beyond the spectral analysis of the light.

Thanks.

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Re: APOD: NGC 4755: A Jewel Box of Stars (2010 Aug 17)

Post by mexhunter » Tue Aug 17, 2010 1:46 pm

Hello to all:
A few years ago, I had the chance to see it with a small telescope, from Acapulco, Mexico.
It is really a jewelry box.
Many grettings
Cesar
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Re: APOD: NGC 4755: A Jewel Box of Stars (2010 Aug 17)

Post by Chappy » Tue Aug 17, 2010 7:32 pm

It looks like a few of the stars in this cluster may have companion stars very nearby.
Does anyone here know if there are a few binary systems in this cluster where the companion star is close enough to orbit the other companion but far enough away to be visible as two separate stars at this range? Can binary star systems orbit far enough away to be visible as 2 stars, or are their mutual gravity too strong to allow them to be that far away from one another?
This one may be an example, I don't know, but it stood out to me. It could also just be an illusion from a star further behind the other, but there are a couple of very close looking stars in this cluster.

Image

I love these smaller clusters, they allow us to see the beauty of the individual cluster stars against a colorful backdrop of distant stars/galaxies, without washing each other out because of the huge number of them.

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RE: APOD: NGC 4755: A Jewel Box of Stars (2010 Aug 17)

Post by nickc c » Tue Aug 17, 2010 9:45 pm

The pic of the day showing the "Jewel Box" says they are 10M years old. That seems extremely young. Did they mean 10B?

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Re: RE: APOD: NGC 4755: A Jewel Box of Stars (2010 Aug 17)

Post by Chris Peterson » Tue Aug 17, 2010 11:22 pm

nickc c wrote:The pic of the day showing the "Jewel Box" says they are 10M years old. That seems extremely young. Did they mean 10B?
No, 10 million. That is a typical age for an open cluster. Open clusters have short lifetimes, since they are only loosely bound by gravity.
Chris

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Ann
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Re: APOD: NGC 4755: A Jewel Box of Stars (2010 Aug 17)

Post by Ann » Wed Aug 18, 2010 5:21 pm

For me as a color freak, it is extremely interesting that the lone red supergiant isn't the visually brightest of the stars. The situation is identical in another mostly blue cluster, NGC 3293:

Image

The red supergiant here is very bright, but not obviously brighter than the brightest blue stars.

M 41is another type of cluster, much older than the Jewel Box or NGC 3293, and its stars are not nearly as massive. Here the red giant (not supergiant) dominates its cluster in a way that the red supergiants do not dominate theirs (and the bright blue star at lower left is not part of the cluster):

Image

Similarly, the red giant of cluster M6 is the brightest of its cluster:

Image

Also Betelgeuse is visually fainter than Rigel, even though Rigel is farther away. The stars of Orion's Belt may also beat Betelgeuse in visual output, in view of the fact that they are definitely farther away than the red supergiant.

At least Antares most definitely dominates Scorpius.

Ann
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