APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06)

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APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06)

Post by APOD Robot » Mon Apr 06, 2015 4:11 am

Image NGC 3293: A Bright Young Star Cluster

Explanation: Hot blue stars shine brightly in this beautiful, recently formed galactic or "open" star cluster. Open cluster NGC 3293 is located in the constellation Carina, lies at a distance of about 8000 light years, and has a particularly high abundance of these young bright stars. A study of NGC 3293 implies that the blue stars are only about 6 million years old, whereas the cluster's dimmer, redder stars appear to be about 20 million years old. If true, star formation in this open cluster took at least 15 million years. Even this amount of time is short, however, when compared with the billions of years stars like our Sun live, and the over-ten billion year lifetimes of many galaxies and our universe. Pictured, NGC 3293 appears just in front of a dense dust lane and red glowing hydrogen gas emanating from the Carina Nebula.

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Ann
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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by Ann » Mon Apr 06, 2015 6:27 am

Oh, this is a lovely RGB image! And NGC 3293 is such an interesting cluster. For one thing, it is so rich and compact. Few other open clusters look like that. The Jewel Box, for example, looks compact from afar, but seems to draw apart at a closeup. NGC 3293 remains compact.

It is interesting to hear that the red stars are older than the blue ones in this cluster. There is one very obvious red star in NGC 3293, SAO 238228 or V361 Carina. This star is fainter than two of the blue stars in NGC 3293 in V light, but it is so bright in infrared light that its total energy output must be greater than that of its blue siblings. To me this looks like a typical bright M-type cluster supergiant, and I always thought, since I first saw pictures of this cluster, that the red whopper must either be a bit older or more massive than the blue stars in NGC 3293.

In today's APOD, there is another red star to the lower right of obvious SAO 238228, and that is HD 303076. I don't know much about it, but to me it looks like an outlier of NGC 3293, and it looks like it sort of belongs to its big red brother. Perhaps star formation started in this general vicinity and then progressed to the upper left, into what is now the main part of the cluster? There are a few other red stars at the lower right edge of the cluster, which might be remnants of the first wave of star formation here.

What a beautiful picture this is, and what an interesting cluster it shows us!

Ann
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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by BillBixby » Mon Apr 06, 2015 5:40 pm

My first thought on seeing today's APOD was that Ann was going to love this one. My second thought was how beautiful the picture was. Third thought was to save it to my computer. Now I think it is time for a cup of coffee.

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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by Guest1 » Mon Apr 06, 2015 7:19 pm

Hello. After studying this picture, I have found a curious green object in the upper middle of the picture. I don't know if this picture is a color enhanced photo or not. Anyway I was just wondering if anyone else noticed it.

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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by Lithopsian » Mon Apr 06, 2015 10:00 pm

Guest1 wrote:Hello. After studying this picture, I have found a curious green object in the upper middle of the picture. I don't know if this picture is a color enhanced photo or not. Anyway I was just wondering if anyone else noticed it.
The cluster image consists of a number of filtered images overlaid in artificial colours. This is the case with the majority of modern astronomical images. Here we have two visual filters, plus IR plus H-alpha. At full scale it shows a number of artefacts that I can't imagine are purely optical.

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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by Ann » Tue Apr 07, 2015 1:50 am

Lithopsian wrote:
Guest1 wrote:Hello. After studying this picture, I have found a curious green object in the upper middle of the picture. I don't know if this picture is a color enhanced photo or not. Anyway I was just wondering if anyone else noticed it.
The cluster image consists of a number of filtered images overlaid in artificial colours. This is the case with the majority of modern astronomical images. Here we have two visual filters, plus IR plus H-alpha. At full scale it shows a number of artefacts that I can't imagine are purely optical.
The colors in this picture are probably less "artificial" than the colors in many other astronomy images. The filters used for this picture are blue, green, H-alpha(red) and infrared. That is not far from how the human eye sees color, since we have receptors for blue, green and red light. We can be certain that the picture of NGC 3292 taken through the blue filter has been shown as blue, the "green-filter-image" has been shown as green, and the Ha and infrared-filter images have both been mapped as red. That's not too far from "reality".

I wasn't able to spot a green object in the upper middle of the picture, but it is true that one star, at about 8 o'clock, has a curious green halo around it. This is somewhat baffling, since the color of the star (HD 92121) is unremarkable, about +0.2. However, one thing sets this star apart from all the other bright stars in this image, and that is that HD 92121 belongs to spectral class A. All the other bright stars here are either bluer than spectral class A (spectral classes O and B) or redder than spectral class A (K and M). Since HD 92121 belongs to spectral class A its "energy distribution" will be different than the really hot and really cool stars here, and it will emit more of its energy in the form of green light. But surely there must be stars of spectral class A inside NGC 3293? Oh, absolutely, but the main sequence A-type stars are not so bright, and they don't have any obvious halos in this image. Chances are that HD 92121 may belong to NGC 3293, but if so it is probably an older and somewhat evolved member.

In any case the green halo is an artifact. HD 92121 has four well separated and distinct halos: a large green one, centered on the star, a smaller blue one moderately well centered on the star, a blue ring to the upper right, and a small, sharp red ring to the right of the star. The rings are very obvious artifacts, and the distinct green halo is, too.

Ann
Last edited by Ann on Tue Apr 07, 2015 7:33 am, edited 1 time in total.
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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by starsurfer » Tue Apr 07, 2015 7:10 am

A beautiful cluster that is also known as the Gem Cluster! A wider view by Don Goldman shows more of the surrounding nebulosity, which is known as RCW 51. This image by Steve Crouch also shows the reflection nebulosity around the cluster, which isn't as apparent in the ESO image. This widefield image by Tanja Schmitz also includes the nebula NGC 3324 and the large filamentary WR 23 Wolf Rayet nebula, which is one of the largest WR nebulae with a size of approximately 50 light years.

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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by DavidLeodis » Tue Apr 07, 2015 12:58 pm

On enlarging the image (click on it when online) there are a number of interesting red rings to be seen in various parts of the image. I wonder if they are image artefacts, or if not what are they?

On looking in the ESO website I learnt a new word, namely 'organigram' :wink: . It's an organisational chart :).

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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by Ann » Tue Apr 07, 2015 2:09 pm

DavidLeodis wrote:On enlarging the image (click on it when online) there are a number of interesting red rings to be seen in various parts of the image. I wonder if they are image artefacts, or if not what are they?

On looking in the ESO website I learnt a new word, namely 'organigram' :wink: . It's an organisational chart :).
As I said in my second post, the red rings are definitely artifacts. :wink:

Thanks for teaching us a new word!

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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by Nitpicker » Wed Apr 08, 2015 12:27 am

I wonder why this cluster (The Gem Cluster, NGC 3293) appears to be so much less famous than the nearby Kappa Crucis (The Jewel Box Cluster, NGC 4755)? I'd never seen it before this beautiful APOD, but the two seem very similar.

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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by Ann » Wed Apr 08, 2015 6:09 am

Nitpicker wrote:I wonder why this cluster (The Gem Cluster, NGC 3293) appears to be so much less famous than the nearby Kappa Crucis (The Jewel Box Cluster, NGC 4755)? I'd never seen it before this beautiful APOD, but the two seem very similar.
http://en.wikipedia.org/wiki/Jewel_Box_ ... cluster%29 wrote:
The Jewel Box, Kappa Crucis Cluster, NGC 4755, is an open cluster in the constellation Crux, originally discovered by Nicolas Louis de Lacaille during 1751–1752. This famous cluster was later named the Jewel Box by Sir John Herschel when he described its telescopic appearance as "a casket of variously coloured precious stones." It is easily visible to the naked eye as a hazy star some 1.0° southeast of the first-magnitude star Beta Crucis.
So why is the Jewel Box famous? Let's see...Image

One. Famous discoverer. (I mean Sir John Herschel, famous son of a famous father and cataloger of southern skies - let's forget about that Nicolas Louis de Lacaille guy).

Two. Fancy name.

Three. Wonderful description.

Four. Top southern location. Located right next to Beta Crucis, itself unmistakable as a crucial(!) member of the famous Southern Cross. (NGC 4755 is another name for the Jewel Box.)


Let's compare the assets of NGC 3293 with those that can be mustered by the Jewel Box. Famous discoverer? Nope, only the Lacaille guy again. Fancy name? Well, the Gem Cluster isn't bad, but who has heard about it? Wonderful description? None is to be had. Easy location? No. Bright fifth magnitude cluster NGC 3293 is located in the general direction of faint sixth magnitude star Eta Carina. It is pretty close to bright fourth magnitude star HD 90853, does it help? Even closer to faint fourth magnitude K-type star HD 91942. Still doesn't ring a bell? Well, I guess the closest first magnitude star to NGC 3293 is... Alpha Crucis?

But in photos at least, NGC 3293 looks better than the Jewel Box, at least in my opinion.

Ann
Last edited by Ann on Wed Apr 08, 2015 7:34 am, edited 1 time in total.
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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by Nitpicker » Wed Apr 08, 2015 7:21 am

Thanks Ann, I suppose you're right.

There sure is a lot going on in this part of the sky, if you look at a decent and wide enough photo. Here's a nice one I found, which I've defaced (sorry) with big green arrows pointing to the two clusters:
Crux_Carina_nitpickered.jpg
Credit: Sergio Eguivar http://www.baskies.com.ar/PHOTOS/Crux%2 ... Carina.jpg
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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by Ann » Wed Apr 08, 2015 8:25 am

Thanks for the map, Nit!

I really think location is the key. Location, location, location. The first galaxy ever to be shown to have spiral structure was M51, and another Messier galaxy, M101, is surely one of the most-photographed galaxies in the sky. Where are these famous galaxies located? Well, close to the Big Dipper, not too far away from Eta Ursa Majoris, Alkaid, the end star in the Dipper's handle.

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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by starsurfer » Wed Apr 08, 2015 10:27 am

Nitpicker wrote:Thanks Ann, I suppose you're right.

There sure is a lot going on in this part of the sky, if you look at a decent and wide enough photo. Here's a nice one I found, which I've defaced (sorry) with big green arrows pointing to the two clusters:
Crux_Carina_nitpickered.jpg
Credit: Sergio Eguivar http://www.baskies.com.ar/PHOTOS/Crux%2 ... Carina.jpg
The image also shows the Southern Pleiades (IC 2602) south of the Eta Carinae Nebulae! One of the best regions of the Milky Way (and also well studied as well)! :D

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Re: APOD: NGC 3293: A Bright Young Star Cluster (2015 Apr 06

Post by starsurfer » Wed Apr 08, 2015 10:28 am

DavidLeodis wrote:On enlarging the image (click on it when online) there are a number of interesting red rings to be seen in various parts of the image. I wonder if they are image artefacts, or if not what are they?
ESO images seem to have haloes around the brighter stars, which is a little annoying.