APOD: Ghost of the Cepheus Flare (2010 Oct 30)

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APOD: Ghost of the Cepheus Flare (2010 Oct 30)

Post by APOD Robot » Sat Oct 30, 2010 3:59 am

Image Ghost of the Cepheus Flare

Explanation: Spooky shapes seem to haunt this starry expanse, drifting through the night in the royal constellation Cepheus. Of course, the shapes are cosmic dust clouds faintly visible in dimly reflected starlight. Far from your own neighborhood on planet Earth, they lurk at the edge of the Cepheus Flare molecular cloud complex some 1,200 light-years away. Over 2 light-years across the ghostly nebula known as vdB 141 or Sh2-136 is near the center of the field. The core of the dark cloud on the right is collapsing and is likely a binary star system in the early stages of formation.

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orin stepanek
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Re: APOD: Ghost of the Cepheus Flare (2010 Oct 30)

Post by orin stepanek » Sat Oct 30, 2010 4:15 am

I like this ghost! :mrgreen: Actually it looks like two ghosts in the upper right hand area. A big one and a little one. Might they be talking to each other? probably making plans for Halloween! :lol:
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Re: APOD: Ghost of the Cepheus Flare (2010 Oct 30)

Post by geckzilla » Sat Oct 30, 2010 7:36 am

Ahhh this is a great Halloween themed APOD. I was hoping for something other than the witch head again and glad she got a much deserved break!
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Re: APOD: Ghost of the Cepheus Flare (2010 Oct 30)

Post by orin stepanek » Sat Oct 30, 2010 11:36 am

geckzilla wrote:Ahhh this is a great Halloween themed APOD. I was hoping for something other than the witch head again and glad she got a much deserved break!
Aah; but Halloween is Sunday. We could get her (the Witch) yet. :mrgreen:
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Re: APOD: Ghost of the Cepheus Flare (2010 Oct 30)

Post by Redbone » Sat Oct 30, 2010 12:57 pm

Great pic!

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Ann
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Re: APOD: Ghost of the Cepheus Flare (2010 Oct 30)

Post by Ann » Sat Oct 30, 2010 7:18 pm

As a color freak who loves blue things, I was of course immediately fascinated by what looks like a bright blue double star in the picture. Thanks to my astronomy software I was able to identify the brighter component of this double star as HD 202986, a magnitude 7.92 F0 star seen from a distance of 245 light-years, with an absolute visual luminosity of 3.19 times that of the Sun and a color index of 0.42. That makes it yellower than A7 star Altair (color index 0.22) but bluer than F5 star Mirphak (color index 0.48). Altair looked blue to me when I observed it with a 14 inch telescope, but Mirphak looked white. I suspect that HD 202986 would also look white to me, but since it is clearly bluer than the Sun, it is okay to show it as blue in a photograph.

But the other component of the double star is another matter. According to my software it is a magnitude 9.36 star of spectral class G5 and with a color index of 0.68, yellower than that of the Sun, whose color index according to wikipedia is 0.656±0.005. There is no reason to show this star as blue, except that its whitish color might be overwhelmed by the slightly blue color of the brighter component.

It is interesting to see that so many of the stars in the picture seem to have a yellowish-brown color. No doubt they are reddened by the dust that is so prevalent in the constellation of Cepheus. Vad den Berg 141 is not so far away from the Iris Nebula, which is part of a huge dusty complex:
A great picture of all the dust surrounding the Iris Nebula was recently posted here at SA* by Bogdan Jarzyna:
My point is that Cepheus is really a very dusty constellation. At the same time it is home to many hot blue OB stars, but these stars don't look blue to us for two reasons. One, they are far away. The OB stars of Cepheus are generally much farther away than the comparatively nearby numerous bright blue stars in Centaurus, Scorpius and the Southern Cross, which are generally 300 to 400 light-years distant.

Image

The many blue stars of Centaurus are generally "only" about 400 light-years away...

The bright blue stars of Orion are at least twice as far away as those in Scorpius, Centaurus and Crux, but unlike the similarly distant stars in Cepheus their color is relatively unaffected by dust:

Image

But Cepheus is dusty. The intervening dust is between us and the most intensely starforming parts of the constellation, near O stars Lambda Cephei and 19 Cephei.The constellation is full of great stars, but we don't see them well because they are far away and strongly reddened by dust. To me, constellation Cepheus is like an itty bitty tiny baby brother of an ULIRG, an Ultra Luminous InfraRed Galaxy, whose light is smothered by all the dust created by its own intense star formation. So I'd say that it is no coincidence that we find the ghostly nebula of today's APOD in Cepheus; if you are looking for dust in our galaxy, Cepheus is as good a place as any to start.

Finally, I can't keep this truly great annotated picture of Cepheus from you. The picture is big, so I'll only post it as a link, and it is not in English, but you should be able to understand what the designations refer to. "Nebulosa Iris", for example, is obviously the Iris Nebula.

http://www.telefonica.net/web2/astromod ... saico-.jpg

I made a mistake with that link before. but this is the real link, I promise. Do look at it, because it's great!

Ann
Last edited by Ann on Sun Oct 31, 2010 4:26 pm, edited 1 time in total.
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Re: APOD: Ghost of the Cepheus Flare (2010 Oct 30)

Post by BMAONE23 » Sat Oct 30, 2010 7:59 pm


judy

Re: APOD: Ghost of the Cepheus Flare (2010 Oct 30)

Post by judy » Sat Oct 30, 2010 8:25 pm

wonderful picture! thank you.

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Re: APOD: Ghost of the Cepheus Flare (2010 Oct 30)

Post by Ann » Sun Oct 31, 2010 4:09 am

Thanks, BMAONE 123! :D

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Re: APOD: Ghost of the Cepheus Flare (2010 Oct 30)

Post by DavidLeodis » Sun Oct 31, 2010 10:42 am

The "this starry expanse" link (and clicking on the APOD) brings up a wder field-of-view image that is even spookier. :owl: << There does not seem to be a spooky smilie in the APOD list but that one is nearish (I like owls but some people think they are a bit spooky).

mpharo

Re: APOD: Ghost of the Cepheus Flare (2010 Oct 30)

Post by mpharo » Fri Nov 05, 2010 9:24 pm

Ghost of the Cepheus Flare (2010 Oct 30)

The ghostly nebula looks sort of like a number of snowy mountain peaks at night. Besides the blue binary star system beneath the nebula, there is another catchy feature: a prominent yellowish star (maybe a G-type) on top of the ghost's head.



Michael Pharo

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