Planetary Nebula in Globular Cluster.

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Planetary Nebula in Globular Cluster.

Postby orin stepanek » Tue Nov 22, 2011 11:37 pm

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NASA's Hubble Finds Stellar Life and Death in a Globular Cluster
A new NASA Hubble Space Telescope image shows globular cluster NGC 1846, a spherical collection of hundreds of thousands of stars in the outer halo of the Large Magellanic Cloud, a neighboring dwarf galaxy of the Milky Way that can be seen from the southern hemisphere. The most intriguing object, however, doesn't seem to belong in the cluster. It is a faint green bubble in the white box near the bottom center of the image. This so-called "planetary nebula" is the aftermath of the death of a star.

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Re: Planetary Nebula in Gkobular Cluster.

Postby neufer » Wed Nov 23, 2011 12:35 am

The "Gkobular Cluster" almost became your 3,000th post.
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Re: Planetary Nebula in Gkobular Cluster.

Postby orin stepanek » Wed Nov 23, 2011 12:57 am

neufer wrote:The "Gkobular Cluster" almost became your 3,000th post.

Thanks Art; and here it is. :D 8-) :clap: :clap: :b: :wink:
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Re: Planetary Nebula in Gkobular Cluster.

Postby Ann » Wed Nov 23, 2011 1:58 am

Congratulations on your 3000th post, Orin! :-D :clap: :-D :clap: :-D :clap:

You beat me to the latest Hubble picture, too. I checked http://hubblesite.org/ yesterday, but there was no new image there then.

As for the new image, I wonder how they can be so sure that the planetary nebula doesn't belong to the cluster.

Image
The globular itself appears to be a comparatively metal-rich one, because it doesn't appear to have a blue horizontal branch of stars.

Take a look at this Hubble image of M13, which is a metal-poor cluster. Look carefully, and you will see that there is a large number of small blue stars in the cluster.

These blue stars are blue horizontal branch stars, and the only stars that reach this position in their evolutionary track are metal-poor stars.

Image
A color-magnitude plot of the stars in a metal-poor globular cluster will look something like this. You can see the blue horizontal stars to the upper left in this picture. But there is no such obvious population to be found in the latest Hubble image of NGC 1846.

If you go to this page, however, you can enlarge the Hubble image of NGC 1846. At the JPEG 2.64 MB magnification, I can see a relatively numerous population of smallish blue stars, which are numerous and similar enough to be some kind of population of blue stars in NGC 1846. But they stand out quite poorly, I must say.


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Hubble Heritage: Globular Cluster NGC 1846 (2011 Nov)

Postby bystander » Tue Nov 29, 2011 10:33 pm

Globular Cluster NGC 1846
Hubble Heritage (STScI/AURA) | 2011 Nov 22
Large Magellanic Cloud Cluster Member May be a Planetary Nebula

In a "Where's Waldo" montage of stellar proportions, the Hubble Space Telescope image of the globular cluster NGC 1846 holds some non-typical treasures. The spherical collection of hundreds of thousands of stars resides in the outer halo of the Large Magellanic Cloud (LMC), our dwarf galaxy neighbor.

Bright stars in the cluster glow in intense shades of red and blue, indicative of their temperatures. The majority of fainter stars are bluish-white in color. Hidden deep between the stars of NGC 1846 are some optical gems. Slightly up and to the right of the center of the cluster, a bright edge-on galaxy can be found. Further out at the lower left is a background face-on spiral galaxy, shaped like a "Bull's Eye." More and more galaxies can be found with a keen eye - some with elongated shapes, others reddish in color.

But the most intriguing object, and the one that just doesn't seem to belong, is a faint, round, green bubble near the bottom center of the image. This is the aftermath of a stellar explosion of a star, known as a planetary nebula. The remnant central star can be seen neatly confined inside the bubble.

The bubble's color comes from the fact that Hubble's broad filters were used to examine the starlight from the cluster. Planetary nebulae, like this one, emit bright oxygen gas, which is being picked up by the green filter. It is uncertain whether the star that is now a planetary nebula is a member of NGC 1846. Measurements of the motion of the cluster stars and the planetary nebula's central star are close enough to rule in favor of the dying star being a cluster member.

This Hubble image was taken with the Advanced Camera for Surveys in January of 2006. The cluster was observed in filters that isolate blue, green, and infrared starlight. As a member of the LMC, NGC 1846 is located roughly 160,000 light-years away in the direction of the constellation Doradus.

Credit: NASA, ESA, Hubble Heritage (STScI/AURA)
Acknowledgment: P. Goudfrooij (STScI)
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Re: Planetary Nebula in Globular Cluster.

Postby neufer » Tue Nov 29, 2011 11:01 pm

http://en.wikipedia.org/wiki/The_Boy_with_Green_Hair wrote:
Click to play embedded YouTube video.

The Boy with Green Hair

<<The Boy with Green Hair is a 1948 American comedy-drama film directed by Joseph Losey.[1][2] It stars Dean Stockwell as Peter, a young war orphan who is subject to ridicule after he awakens one morning to find his hair mysteriously turned green. Co-stars include Pat O'Brien, Robert Ryan, and Barbara Hale.

Finding a curiously silent young runaway boy (Stockwell) whose head has been completely shaved, small-town police call in a psychologist (Ryan) and discover that he is a war orphan named Peter Frye. Moving in with an understanding retired actor named Gramps (O'Brien), Peter starts attending school and generally begins living the life of a normal boy until his class gets involved with trying to help war orphans in Europe and Asia.

Peter soon realizes that—like the children on the posters, whose images haunt him—he, too, is a war orphan. The realization about his parents and the work helping the orphans makes Peter turn very serious, and he is further troubled when he overhears the adults around him talking about the world preparing for another war. Peter awakens the next day and his hair has turned green, prompting him to run away after being taunted by the townspeople and his peers. Suddenly, appearing before him in a lonely part of the woods are the orphaned children whose pictures he saw on the posters.

They tell him that he is a war orphan, but that with his green hair he can make a difference and must tell people that war is dangerous for children. He leaves determined to deliver his message to any and all. Upon his return, the townspeople chase Peter, and even Gramps tries to encourage him to consider shaving his hair so that it might grow back normally. He agrees to get his head shaved, and the town barber does the job—that night, however, Peter runs away. Later reunited with Gramps, Peter learns that there are adults out there who accept what he has to say and want him to go on saying it. He's sure that his hair will grow back in green again, and he will continue to carry his message.

The 2009 film Battlestar Galactica: The Plan, which also starred Dean Stockwell, made extensive reference to The Boy with Green Hair. Director Edward James Olmos, a fan of Stockwell's earlier film, had a replica of Peter's costume created for a war orphan character in The Plan named John. Olmos stated that he wanted John to have green hair, but the studio refused to allow it.>>
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