APOD: A Dark and Dusty Sky (2015 May 22)

Comments and questions about the APOD on the main view screen.
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APOD: A Dark and Dusty Sky (2015 May 22)

Post by APOD Robot » Fri May 22, 2015 4:11 am

Image A Dark and Dusty Sky

Explanation: In the dusty sky toward the constellation Taurus and the Orion Arm of our Milky Way Galaxy, this broad mosaic follows dark and faint reflection nebulae along the region's fertile molecular cloud. The six degree wide field of view starts with long dark nebula LDN 1495 stretching from the lower left, and extends beyond the (upside down) bird-like visage of the Baby Eagle Nebula, LBN 777, at lower right. Small bluish reflection nebulae surround scattered fainter Taurus stars, sights often skipped over in favor of the constellation's better known, brighter celestial spectacles. Associated with the young, variable star RY Tau, the yellowish nebula VdB 27 is toward the upper left. Only 400 light-years or so distant, the Taurus molecular cloud is one of the closest regions of low-mass star formation. At that distance this dark vista would span over 40 light-years.

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Craine
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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by Craine » Fri May 22, 2015 11:51 am

"Dark and dusty, painted on the sky
Misty taste of moonshine, teardrop in my eye"

From "Country Road" by John Denver.

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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by geckzilla » Fri May 22, 2015 12:07 pm

I'm very fond of these sorts of images. This one pleases my sense of aesthetics.
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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by starsurfer » Fri May 22, 2015 3:45 pm

geckzilla wrote:I'm very fond of these sorts of images. This one pleases my sense of aesthetics.
It is an incredibly pleasing image, also generally I really like mosaics. I like vistas that appear to be cosmic watercolour paintings. I thought I recognised Scott Rosen's name and he did an amazing widefield image of Sh2-129 with the possible outflow nebula Ou 4. He also has a nice mosaic of the Iris Nebula that includes Gyulbudaghian's Nebula! :D

Also in today's APOD, the large blue reflection nebula to the right of vdB27 is Ced 30, a closeup by Adam Block.

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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by JimK87654 » Fri May 22, 2015 5:00 pm

What is the size of the "dust"? Is it dust in the household sense or much finer or larger? Thanks.

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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by Chris Peterson » Fri May 22, 2015 5:11 pm

JimK87654 wrote:What is the size of the "dust"? Is it dust in the household sense or much finer or larger? Thanks.
From a mass standpoint, most of the "dust" consists of simple molecules, mostly H2. But the opacity is primarily from silicates and carbonates, which range in size from a few molecules up to perhaps 100 nm. Household dust is much more diverse, and much of it is larger, in the 1-100 micrometer range.
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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by Ann » Fri May 22, 2015 5:17 pm

starsurfer wrote: Also in today's APOD, the large blue reflection nebula to the right of vdB27 is Ced 30, a closeup by Adam Block.
Thanks for that, starsurfer! :D

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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by Ron-Astro Pharmacist » Fri May 22, 2015 6:25 pm

If the sky is full of treasures like this I can begin to see why astrophotographers get hooked then swallowed by choice to learn their trade. What's this, about 0.04% of the sky at that distance? There's a lot of sky to use as their canvas! Nice choice and well done Scott! :clap:
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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by Chris Peterson » Fri May 22, 2015 7:03 pm

Ron-Astro Pharmacist wrote:What's this, about 0.04% of the sky at that distance? There's a lot of sky to use as their canvas!
Not just that, but there are countless ways this (or any other) 0.04% of the sky can be imaged- filter choices, color balance choices- that can give us radically different views, both scientific and aesthetic.
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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by Craig Willford » Fri May 22, 2015 9:04 pm

In the hyperlink to LDN 1495, it talks of the NH3 being gravitationally bound (some of it) and some of it being pressure bound and that each of those can collapse into protostars.

I wonder how much of such material collapse into "solar systems" but with an inadequately massive center object to trigger nuclear "fire" to make it a star?

In other words, how much mass is floating around in our galaxy dark and invisible, but for minor (very minor) gravitational lensing?

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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by Chris Peterson » Fri May 22, 2015 9:15 pm

Craig Willford wrote:In other words, how much mass is floating around in our galaxy dark and invisible, but for minor (very minor) gravitational lensing?
Probably none. Because such matter still has an electromagnetic signature- in the IR typically, but depending on conditions it could be in the UV or radio spectrum, as well.

That is, it's not that there isn't essentially non-luminous matter floating around, it's that it isn't invisible.
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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by Craig Willford » Fri May 22, 2015 11:07 pm

Chris Peterson wrote:
Craig Willford wrote:In other words, how much mass is floating around in our galaxy dark and invisible, but for minor (very minor) gravitational lensing?
Probably none. Because such matter still has an electromagnetic signature- in the IR typically, but depending on conditions it could be in the UV or radio spectrum, as well.

That is, it's not that there isn't essentially non-luminous matter floating around, it's that it isn't invisible.
Chris, as the black body radiation fades into deeper and deeper IR, then radio wave frequencies, while the body cools from the loss of energy by such radiation, wouldn't the bodies become invisible to our equipment?

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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by Chris Peterson » Fri May 22, 2015 11:57 pm

Craig Willford wrote:
Chris Peterson wrote:
Craig Willford wrote:In other words, how much mass is floating around in our galaxy dark and invisible, but for minor (very minor) gravitational lensing?
Probably none. Because such matter still has an electromagnetic signature- in the IR typically, but depending on conditions it could be in the UV or radio spectrum, as well.

That is, it's not that there isn't essentially non-luminous matter floating around, it's that it isn't invisible.
Chris, as the black body radiation fades into deeper and deeper IR, then radio wave frequencies, while the body cools from the loss of energy by such radiation, wouldn't the bodies become invisible to our equipment?
The dust and gas tend to hang out together. And the non-luminous stuff is necessarily extremely tenuous, or its self-gravity would pull it back to together again. In those regions, the gas is actually very hot, and shines dimly in the UV and x-ray. It can also show up as neutral hydrogen in radio images.
Chris

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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by Boomer12k » Sat May 23, 2015 1:18 am

Thank you for the LINKS!!!
The Orion Arm Link is really great!! Zooming out is cool....( I thought it was just the Orion SPUR from another APOD..., guess it has been upgraded...)

Did not know we had so many arms...Maybe S.P.E.C.T.R.E should change their mascot and logo from an Octopus to the Galaxy...but then G.A.L.A.X.Y... from the Flint movies would complain...
:lol2:

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Re: APOD: A Dark and Dusty Sky (2015 May 22)

Post by Boomer12k » Sat May 23, 2015 4:05 am

I see faces, and ghosts...I'm really scared...

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