Starship Asterisk*

by **neufer** » Fri Dec 19, 2008 10:48 pm

Chris Peterson wrote:
zbvhs wrote:To my eye, The Dumbbells aren't shaped like dumbbells (the kind that weight-lifters use) but are more toroidal in shape with jets coming out of the doughnut hole.
I'm pretty sure the names were bestowed by visual observers. Certainly, through a telescope, these objects are much easier to see as dumbbell shaped (that's because, as is usual for DSOs, you can't see much through a telescope except for faint gray fuzzy things, with little detail. So the outside shape is about all that's available for naming). Many objects, when imaged in detail, don't show much of their visual-based name characteristics.

They look more like Dumbledores
------------------------------------------------
<<The name "Dumbledore" is an old Devon word for "bumblebee"
and was picked by Rowling because she imagines
[Albus Percival Wulfric Brian Dumbledore]
wandering around the castle humming to himself.>>
.
http://en.wikipedia.org/wiki/Albus_Dumbledore
-----------------------------------------------

by **Chris Peterson** » Fri Dec 19, 2008 10:04 pm

zbvhs wrote:To my eye, The Dumbbells aren't shaped like dumbbells (the kind that weight-lifters use) but are more toroidal in shape with jets coming out of the doughnut hole.

I'm pretty sure the names were bestowed by visual observers. Certainly, through a telescope, these objects are much easier to see as dumbbell shaped (that's because, as is usual for DSOs, you can't see much through a telescope except for faint gray fuzzy things, with little detail. So the outside shape is about all that's available for naming). Many objects, when imaged in detail, don't show much of their visual-based name characteristics.

by **zbvhs** » Fri Dec 19, 2008 9:47 pm

To my eye, The Dumbbells aren't shaped like dumbbells (the kind that weight-lifters use) but are more toroidal in shape with jets coming out of the doughnut hole.

by **DavidLeodis** » Thu Dec 18, 2008 2:36 pm

Thank you bystander and Chris for your replies, which are greatly appreciated. I did see the line between the two images but I wondered if that could simply be where the two images in an otherwise same area of view were joined. That the two nebula are not in the same area of view is not at all obvious, at least to me!

by **Chris Peterson** » Thu Dec 18, 2008 2:26 pm

DavidLeodis wrote:In the explanation to the APOD it states the "images were made at the same scale, so the apparent size difference is mostly because one is closer". I am unsure though if their apparent position to each other is as seen in the picture, that is can they be seen together like they appear, or is it just a picture showing an image of each nebula that have just been put next to each other but which in reality cannot be seen together. I hope that makes sense about what I'm trying to find out! :)

The two objects are in different parts of the sky (70° separation). You're seeing two images side-by-side. In fact, if you can't see the rather obvious division between the two, which is darker than the sky background, your monitor is too dark, and needs adjustment. Check this grayscale bar and make sure you can see all 13 segments.

by **bystander** » Thu Dec 18, 2008 2:21 pm

DavidLeodis wrote:In the explanation to the APOD it states the "images were made at the same scale, so the apparent size difference is mostly because one is closer". I am unsure though if their apparent position to each other is as seen in the picture, that is can they be seen together like they appear, or is it just a picture showing an image of each nebula that have just been put next to each other but which in reality cannot be seen together. I hope that makes sense about what I'm trying to find out!

They are not in the same part of the sky and can not be seen together.

M27 - Dumbbell Nebula
Vulpecula
RA 19h 59.6m
Dec +22° 43.3′
Dist 1,360 ly

M76 - Little Dumbbell
Perseus
RA 01h 42.4m
Dec +51° 34.0′
Dist 3,400 ly

by **neufer** » Thu Dec 18, 2008 1:38 pm

DavidLeodis wrote:In the explanation to the APOD it states the "images were made at the same scale, so the apparent size difference is mostly because one is closer". I am unsure though if their apparent position to each other is as seen in the picture, that is can they be seen together like they appear, or is it just a picture showing an image of each nebula that have just been put next to each other but which in reality cannot be seen together. I hope that makes sense about what I'm trying to find out!

`I know what you're thinking about,' said Tweedledum; `but it isn't so, nohow.'

`Contrariwise,' continued Tweedledee, `if it was so, it might be; and if it were so, it would be; but as it isn't, it ain't. That's logic.'

by **DavidLeodis** » Thu Dec 18, 2008 12:36 pm

In the explanation to the APOD it states the "images were made at the same scale, so the apparent size difference is mostly because one is closer". I am unsure though if their apparent position to each other is as seen in the picture, that is can they be seen together like they appear, or is it just a picture showing an image of each nebula that have just been put next to each other but which in reality cannot be seen together. I hope that makes sense about what I'm trying to find out!

by **Chris Peterson** » Wed Dec 17, 2008 5:17 pm

rstevenson wrote:Thank you for that. Though I am shocked to my very core by this lack of precision.

It's not quite as bad as the previous post would suggest. M27 is close enough that conventional stellar parallax measurements can be made, using the HST or Hipparcos. Consequently, its distance is known with at least reasonable precision to be 1350 ly (+150, -200). M76 is too far away to use parallax measurements with our current instrumentation, so it does have quite a large uncertainty in distance.

by **rstevenson** » Wed Dec 17, 2008 4:00 pm

Thank you for that. Though I am shocked to my very core by this lack of precision.

Rob

by **neufer** » Wed Dec 17, 2008 3:46 pm

rstevenson wrote:I notice that the sizes of, and therefore the distances to, the two nebulae given in the linked pages in the last line of the APOD post, differ considerably from the sizes and distances given in the APOD post. Is there that much disagreement about these things, still?

Apparently
---------------------------------------------------------
http://www.maa.clell.de/Messier/E/m027.html

<<As for most planetary nebulae, the distance of M27 (and thus true dimension and intrinsic luminosity) is not very well known. Hynes gives about 800, Kenneth Glyn Jones 975, Mallas/Kreimer 1250 light years, while other existing estimates reach from 490 to 3500 light years. Currently, investigations with the Hubble Space Telescope are under work to determine a more reliable and accurate value for the distance of the Dumbbell Nebula.>>
---------------------------------------------------------
http://www.maa.clell.de/Messier/E/m076.html

<<As is not unusual for planetary nebulae, the [M76] distance is poorly known, with estimates between 1,700 and 15,000 light years (the latter value is from Kaufmann's Universe; Kenneth Glyn Jones has the value of 8,200). Accordingly, the true dimensions of the cork is between 0.34x0.72 and 3.1x6.4 light years, while the wings extend up to between 1.3 and 11.3 light years, and the faint halo reaches out to between 2.4 and 21 light years.>>
---------------------------------------------------------

by **rstevenson** » Wed Dec 17, 2008 3:03 pm

Hello,

I notice that the sizes of, and therefore the distances to, the two nebulae given in the linked pages in the last line of the APOD post, differ considerably from the sizes and distances given in the APOD post. Is there that much disagreement about these things, still?

Rob

by **apodman** » Wed Dec 17, 2008 2:47 pm

http://antwrp.gsfc.nasa.gov/apod/ap081217.html

http://antwrp.gsfc.nasa.gov/apod/image/ ... _Lopez.jpg

by **neufer** » Wed Dec 17, 2008 2:22 pm

jimmysnyder wrote:From today's APOD:
Not intended to indicate substandard mental prowess, their popular names refer to their similar, dumbbell or hourglass shapes.
I don't know, next to an Einstein ring
they look to me like nincompoops.

http://apod.nasa.gov/apod/ap081217.html

Art

Neuendorffer

by **jimmysnyder** » Wed Dec 17, 2008 1:33 pm

From today's APOD:

Not intended to indicate substandard mental prowess, their popular names refer to their similar, dumbbell or hourglass shapes.

I don't know, next to an Einstein ring, they look to me like nincompoops.

http://apod.nasa.gov/apod/ap080728.html

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