APOD: Sharpless 249 and the Jellyfish Nebula (2018 Mar 23)

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APOD Robot
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APOD: Sharpless 249 and the Jellyfish Nebula (2018 Mar 23)

Post by APOD Robot » Fri Mar 23, 2018 4:11 am

Image Sharpless 249 and the Jellyfish Nebula

Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic image. Centered in the scene it's anchored right and left by two bright stars, Mu and Eta Geminorum, at the foot of the celestial twin. The Jellyfish Nebula is the brighter arcing ridge of emission with dangling tentacles. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, the Jellyfish Nebula is known to harbor a neutron star, the remnant of the collapsed stellar core. An emission nebula cataloged as Sharpless 249 fills the field at the upper left. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be about 300 light-years across.

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sillyworm2

Re: APOD: Sharpless 249 and the Jellyfish Nebula (2018 Mar 23)

Post by sillyworm2 » Fri Mar 23, 2018 12:50 pm

Maybe Sharpless 249 could be called The SEAHORSE Nebula.

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Re: APOD: Sharpless 249 and the Jellyfish Nebula (2018 Mar 23)

Post by De58te » Fri Mar 23, 2018 1:15 pm

Maybe it's just me but if it wasn't for the Jellyfish Nebula, I would find looking at pictures of Sharpless 249 rather dull. [Groan! But it is better than Uranus jokes]

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Re: APOD: Sharpless 249 and the Jellyfish Nebula (2018 Mar 23)

Post by neufer » Fri Mar 23, 2018 1:41 pm

Click to play embedded YouTube video.
De58te wrote: Fri Mar 23, 2018 1:15 pm
Maybe it's just me but if it wasn't for the Jellyfish Nebula, I would find looking at pictures of Sharpless 249 rather dull.
Art Neuendorffer

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Re: APOD: Sharpless 249 and the Jellyfish Nebula (2018 Mar 23)

Post by MarkBour » Fri Mar 23, 2018 2:52 pm

Does anyone else see a counter-punching St. Nicholas in this image?
(There is an interesting dark feature that looks like he is bleeding from his left cheek.)
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Ann
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Re: APOD: Sharpless 249 and the Jellyfish Nebula (2018 Mar 23)

Post by Ann » Fri Mar 23, 2018 4:23 pm

There is a big and interesting difference between Sharpless 249 and the Jellyfish Nebula. Sharpless 249 is bland and relatively featureless, but the Jellyfish Nebula looks like the aftermath of a wreck. Or rather, it looks like the shattered remains of an explosion, and that is what it is, too.



















Another fascinating coincidence of this part of the sky is that here we see the juxtaposition of red nebulas and orange stars. But orange stars don't make red nebulas - at best, like "red" (really yellow-orange) supergiant Antares, they can make yellow reflection nebulas.

So what's going on in Gemini? Well, for one thing, the two bright orange stars have nothing to do with the red nebulas. Mu Geminorum, the orange star at left, is an M-type giant less than 300 light-years away, much, much closer than the Jellyfish Nebula and much closer than Sharpless 249, too. Eta Geminorum is another M-type giant that is farther away than Mu, but it is less than 400 light-years away and again much closer than the two red nebulas. So not only do the orange stars have nothing to do with the red nebulas, but they probably have nothing to do with each other, either.

For all of that, it is remarkable that two so bright-looking M-type giants are located so close to one another in the sky, because M-type giants are relatively rare. Mu Gem shines at bright third magnitude and Eta Gem at faint third magnitude, and they completely dominate their own little part of the sky. In the picture at right, Mu and Eta are at bottom center. Mu is located "above" Eta, and it is very red-looking due to the fact that it seems to be attached to Sharpless 249. Eta is at lower right from Mu, looking orange rather than red. The small Jellyfish Nebula can be clearly seen between them. To the lower left of Eta is the small, round, bright pink Monkey Head Nebula. To the right of Eta is bright white cluster M35 (and below M35, faint distant cluster NGC 2158 and boring nearby orange star Propus, or 1 Geminorum).

Fascinatingly, between the Monkey Head Nebula and M35 are at least three intrinsically brilliant M-type supergiants, TV Geminorum, BU Geminorum and WY Geminorum. To get so many M-type supergiants in a small patch of sky you need to start out with a lot of hot massive blue stars and have them age and evolve into red giants. And indeed, there really are several hot, distant and dust-reddened B-type stars in the general vicinity: LU Gem, PX Gem and PU Gem. So this part of the sky is dominated by bright, massive but nevertheless aging young stars, which is why it contains both emission nebulas, bright clusters, hot blue B-type supergiant stars and red M-type supergiants.

But eye-catching Mu and Eta Geminorum are not part of the action, but are just passing by in the foreground in their unusual M-type splendor. Oh, and for those of you who are wondering: The obvious blue reflection nebula in Sharpless 249 is van den Bergh 75, centered on 12 Geminorum, a bright A-type giant probably a couple of thousand light-years away, just like Sharpless 249 and many of the bright distant B-type and M-type supergiants here.

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Re: APOD: Sharpless 249 and the Jellyfish Nebula (2018 Mar 23)

Post by starsurfer » Fri Mar 23, 2018 5:23 pm

MarkBour wrote: Fri Mar 23, 2018 2:52 pm Does anyone else see a counter-punching St. Nicholas in this image?
(There is an interesting dark feature that looks like he is bleeding from his left cheek.)
Does anyone see a planetary nebula hidden somewhere?