APOD: Sisters of the Dusty Sky (2010 Nov 18)

[APOD Robot]

Sisters of the Dusty Sky

Explanation: Hurtling through a cosmic dust cloud some 400 light-years away, the lovely Pleiades or Seven Sisters star cluster is well-known for its striking blue reflection nebulae. In the dusty sky toward the constellation Taurus and the Orion Arm of our Milky Way Galaxy, this remarkable image shows the famous star cluster at the upper left. But lesser known dusty nebulae lie along the region's fertile molecular cloud, within the 10 degree wide field, including the bird-like visage of LBN 777 near center. Small bluish reflection nebula VdB 27 at the lower right is associated with the young, variable star RY Tau. At the distance of the Pleiades, the 5 panel mosaic spans nearly 70 light-years.

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[Ann]

The Pleiades look super-lovely as always (no, not as always - thank you, John Davies, for your great image), but what really caught my attention was the weird nebular shape in the center of the picture. APOD robot wrote:

the bird-like visage of LBN 777 near center

Bird-like visage???? You mean like one of these???



I tried to find LBN 777 with my astronomy software, but I could only access LBN 775, right next to LBN 777. This is what my software says about LBN 775:

Maximum diameter: 3000 arcseconds
Emission nebula (questionable)
This object possibly does not exist.
Brightness level: 6 (1=brightest, ... 6=faintest)

Anyway, thanks for the great image! Clearly LBN 777, at least, does exist. But it sure looks weird.

Ann

[yasgur]

LBN 777 looks like a barn owl in that shot.

http://greeneart.com/barn_owl.html

[neufer]

The Pleiades look super-lovely as always (no, not as always - thank you, John Davies, for your great image), but what really caught my attention was the weird nebular shape in the center of the picture. APOD robot wrote:

the bird-like visage of LBN 777 near center

Bird-like visage???? You mean like one of these???

More like this:

The Maltese Falcon (1941) Detective Tom Polhaus: [picks up the falcon] Heavy. What is it? Sam Spade: The, uh, stuff that dreams are made of. Detective Tom Polhaus: Huh?

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[rstevenson]

Hurtling through a cosmic dust cloud some 400 light-years away, ...

Hurtling? So how fast are they moving relative to that dust cloud? And are the sisters bound to each other or just coincidentally moving in more or less the same direction?

Rob

[orin stepanek]

The dust nebula does look kind of like a bird; looking right at the 7 sisters.

Click to play embedded YouTube video.

[neufer]

Hurtling through a cosmic dust cloud some 400 light-years away, ...

Hurtling?

"We hear also through successive ages that shebby choruysh of unkalified muzzlenimiissilehims
that would blackguardise the whitestone ever hurtleturtled out of heaven." - _Finnegans Wake_

Ploughing, actually:

<<[color=#0000FF][b]The Pleiades arrangement is somewhat similar to 'The Plough'[/b][/color]>>

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[url=http://www.naic.edu/~gibson/thesis/]Here[/url] is an interesting composite of the Pleiades: ultraviolet (blue), optical (green), and far-infrared (red). [i]Credit: Steven Gibson[/i]

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[size=145][color=#FF00FF][b]Animation of proper motion in 400 000 years (cross-eyed viewing)[/b][/color][/size]

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[size=175][color=#FF00FF]Carl Gustav M/45[/color][/size]

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Kulsprutepistol m/45 (Kpist m/45), also known as the Carl Gustav M/45 and the Swedish K SMG, is a 9 mm Swedish submachine gun designed by Gunnar Johnsson, adopted in 1945 (hence the m/45 designation), and manufactured in Eskilstuna, Sweden. The m/45 was the standard submachine gun of the Swedish Army from 1945 to the late 1990s.

So how fast are they moving relative to that dust cloud? And are the sisters bound to each other or just coincidentally moving in more or less the same direction?

<<The cluster's relative motion will eventually lead it to be located, as seen from Earth many millennia in the future, passing below the feet of what is currently the constellation of Orion. Also, like most open clusters, the Pleiades will not stay gravitationally bound forever, as some component stars will be ejected after close encounters and others will be stripped by tidal gravitational fields. Calculations suggest that the [~115 million year old] cluster will take about 250 million [more] years to disperse, with gravitational interactions with giant molecular clouds and the spiral arms of our galaxy also hastening its demise.>>

[mexhunter]

Congratulations to John Davis, is an extraordinary shot.
I liked so much.
Greetings
César

[rstevenson]

Thank you Art, for the animation. What a strange chaotic (seemingly, I know) dance we are all engaged in. I'm trying hard to picture that little rectangular segment of our galaxy, with all its different stellar motions, as somehow progressing round the Milky Way, along with all of our billions of neighbours, in a more or less merry-go-round fashion. It might help me to know, relative to the Milky Way's center and plane, in what direction we're looking when we look at the Pleiades.

Rob

[Ann]

Once I start seeing a shape in a certain way, I sometimes find it almost impossible to force my brain to see it differently. When it comes to LBN 777, I kept seeing the darkest, blackest part of it as an open mouth, trying to eat an orange-red morsel above it. (The "morsel" would be the orange star above the nebula.) But finally, finally I'm able to see the black shape as an eye, and I can see now that the bird is facing left, its beak to the left. And the dark brownish shape to the right of the blackest smudge would be some sort of marking on the bird's head.

Art, I must echo Rob abd say thank you for the superior Pleiades animation! But isn't it somehow counterintuitively weird to think that the Pleaides are hurtling - no, ploughing - through space handle first?

Ann

[neufer]

Thank you Art, for the animation. What a strange chaotic (seemingly, I know) dance we are all engaged in. I'm trying hard to picture that little rectangular segment of our galaxy, with all its different stellar motions, as somehow progressing round the Milky Way, along with all of our billions of neighbours, in a more or less merry-go-round fashion. It might help me to know, relative to the Milky Way's center and plane, in what direction we're looking when we look at the Pleiades.

[img3="The shape of the Orion Spur, based on Vázquez, Ruben A.; May, Jorge; Carraro, Giovanni; Bronfman, Leonardo; Moitinho, André; Baume, Gustavo (January 2008). "Spiral Structure in the Outer Galactic Disk."."]http://upload.wikimedia.org/wikipedia/c ... onSpur.png[/img3]

M45 is more in the middle of the Orion Spur/Arm than the Sun is just to the right of the galactic anticenter [near [b][url=http://en.wikipedia.org/wiki/Beta_Tauri]Alnath (β Tau)[/url][/b]] M45 is orbiting clockwise to the right slower that our Sun is thereby drifting back to the left towards the Orion Nebula.

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[rstevenson]

M45 is orbiting clockwise to the right slower that our Sun is
thereby drifting back to the left towards the Orion Nebula.

Thanks again. So if I'm interpreting that right, up in the stereo animation is clockwise in our galaxy's flow. That's the general trend of most of the stars we can see there, but there are some that are moving almost at a right-angle to that flow. I suppose there must be some stars orbiting the galaxy in odd directions compared to the major flow, otherwise there'd be no central bulge and little thickness to the disk. And there's probably a few being kicked out for disrupting the class.

Rob

[neufer]

M45 is orbiting clockwise to the right slower that our Sun is
thereby drifting back to the left towards the Orion Nebula.

Thanks again. So if I'm interpreting that right, up in the stereo animation is clockwise in our galaxy's flow. That's the general trend of most of the stars we can see there, but there are some that are moving almost at a right-angle to that flow. I suppose there must be some stars orbiting the galaxy in odd directions compared to the major flow, otherwise there'd be no central bulge and little thickness to the disk. And there's probably a few being kicked out for disrupting the class.

Up in the stereo animation is clockwise in our galaxy's flow as you say; since these somewhat more distant stars have (on average) a slower rate of galactic clockwise rotation they are generally moving downward in the animation (i.e., counter-clockwise).

One would expect that the average relative motion of non-M45 stars in this (galactic anticenter direction would be about one degree counterclockwise per 600,000 years. However, the stars associated with M45, itself, seem to be going about about one degree counterclockwise per 100,000 years... which, I suppose, might be defined as hurling (although clearly there are much faster individual stars zipping by).