APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 2903
Joined: Fri Dec 04, 2009 3:27 am

APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby APOD Robot » Thu Apr 07, 2016 4:08 am

Image Wolf-Lundmark-Melotte

Explanation: Named for the three astronomers instrumental in its discovery and identification, Wolf - Lundmark - Melotte (WLM) is a lonely dwarf galaxy. Seen toward the mostly southern constellation Cetus, about 3 million light-years from the Milky Way, it is one of the most remote members of our local galaxy group. In fact, it may never have interacted with any other local group galaxy. Still, telltale pinkish star forming regions and hot, young, bluish stars speckle the isolated island universe. Older, cool yellowish stars fade into the small galaxy's halo, extending about 8,000 light-years across. This sharp portrait of WLM was captured by the 268-megapixel OmegaCAM widefield imager and survey telescope at ESO's Paranal Observatory.

<< Previous APOD This Day in APOD Next APOD >>

User avatar
Ann
4725 Å
Posts: 8300
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby Ann » Thu Apr 07, 2016 5:05 am

Today's APOD is a fine picture, and personally I am always happy to see galaxies being showcased as APODs. Particularly if the galaxy rarely has its portrait taken.

NGC 6503. Photo: NASA, ESA, D. Calzetti (University of Massachusetts),
H. Ford (Johns Hopkins University), and the Hubble Heritage Team
The loneliness and remote position of dwarf galaxy Wolf-Lundmark-Melotte at the outskirts of the Local Group, made me think of another nearby but isolated galaxy, NGC 6503.

http://www.nasa.gov/image-feature/goddard/lonely-galaxy-lost-in-space wrote:
Most galaxies are clumped together in groups or clusters. A neighboring galaxy is never far away. But this galaxy, known as NGC 6503, has found itself in a lonely position, at the edge of a strangely empty patch of space called the Local Void.


The Local Void is a huge stretch of space that is at least 150 million light-years across. It seems completely empty of stars or galaxies. The galaxy’s odd location on the edge of this never-land led stargazer Stephen James O’Meara to dub it the “Lost-In-Space galaxy” in his 2007 book, Hidden Treasures.


NGC 6503 is 18 million light-years away from us in the northern circumpolar constellation of Draco. NGC 6503 spans some 30,000 light-years, about a third of the size of the Milky Way.


So Wolf-Lundmark-Melotte, a small irregular galaxy, finds itself at the edge of the Local Group, whereas NGC 6503, a small spiral galaxy, finds itself at the edge of the Local Void. Both are bravely making new stars, but not so many that these galaxies can grow much in size. There is probably not so much gas around at the edge of the cosmic wilderness.

To paraphrase William Wordsworth, I wandered lonely as a star... no, as a cloud. No, as a smallish galaxy where Groups and Voids end.

Ann
Color Commentator

User avatar
bystander
Apathetic Retiree
Posts: 15950
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby bystander » Thu Apr 07, 2016 5:13 am

Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

dl martin, canada

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby dl martin, canada » Thu Apr 07, 2016 7:14 am

what is the red streak at the 6:30 position in the enlarged version?
Last edited by geckzilla on Thu Apr 07, 2016 7:23 am, edited 1 time in total.
Reason: lowercase

User avatar
geckzilla
Ocular Digitator
Posts: 8517
Joined: Wed Sep 12, 2007 12:42 pm

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby geckzilla » Thu Apr 07, 2016 7:29 am

dl martin, canada wrote:what is the red streak at the 6:30 position in the enlarged version?

I would guess an asteroid that was present during one of the observing sessions. If that's right, then the time between imaging was great enough that it was gone or not yet in the frame by the time the data used for the other two channels (green and blue) was collected.
Just call me "geck" because "zilla" is like a last name.

stargazer
Asternaut
Posts: 4
Joined: Mon Sep 21, 2009 7:12 am

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby stargazer » Thu Apr 07, 2016 10:56 am

At 16:00 about half way between Wolf- Lundmark- Melotte and the edge of the picture two interacting galaxies can be seen. Is there a closeup of them in the archive?
You do not have the required permissions to view the files attached to this post.

User avatar
Chris Peterson
Abominable Snowman
Posts: 13037
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby Chris Peterson » Thu Apr 07, 2016 11:41 am

geckzilla wrote:
dl martin, canada wrote:what is the red streak at the 6:30 position in the enlarged version?

I would guess an asteroid that was present during one of the observing sessions. If that's right, then the time between imaging was great enough that it was gone or not yet in the frame by the time the data used for the other two channels (green and blue) was collected.

Maybe, but usually asteroids show up as lines that are sequentially red, green, and blue. The isolated red line makes me think it was a more transient event like a meteor, present only during the red exposure.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
Asterhole
Ensign
Posts: 60
Joined: Fri Oct 30, 2015 2:27 pm
Location: Solar System

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby Asterhole » Thu Apr 07, 2016 11:52 am

dl martin, canada wrote:what is the red streak at the 6:30 position in the enlarged version?

Possibly a distant (red-shifting?) galaxy? There are quite a few of them, whatever they are in this image.
They're all wasted!

NCTom

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby NCTom » Thu Apr 07, 2016 11:56 am

This is such a rich image of background galaxies. I was surprised at how many doublets did not appear to be line-of-sight pairs, but showed true interaction with star streams connecting them. One was mentioned above. Others lie above and to the right of the primary dwarf galaxy.

JPL

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby JPL » Thu Apr 07, 2016 11:59 am

I would like to see a picture of remote objects like this stripped of Milky Way stars, assuming it's possible to identify foreground stars. After a lifetime of viewing such pictures, it is difficult to escape the notion that space is cluttered with stars. Such a doctored image, if honestly labelled, might help dispel this misleading feeling of clutter, and in a sense convey more truthfully what is (isn't) out there.

User avatar
Chris Peterson
Abominable Snowman
Posts: 13037
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby Chris Peterson » Thu Apr 07, 2016 12:01 pm

stargazer wrote:At 16:00 about half way between Wolf- Lundmark- Melotte and the edge of the picture two interacting galaxies can be seen. Is there a closeup of them in the archive?

These objects are only about 9 arcseconds apart, so this is already pretty much a closeup. At this pixel scale, we're close to seeing limited in terms of resolution, although the source image from this instrument is presumably twice as large, so if the conditions were ideal we might see a bit more there. A Hubble image, however, could place several hundred pixels on a side across them- about 5 times the spatial resolution of the OmegaCAM.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

stargazer
Asternaut
Posts: 4
Joined: Mon Sep 21, 2009 7:12 am

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby stargazer » Thu Apr 07, 2016 12:05 pm

Ha! Let's make Hubble to look at them. Where's the control panel? ;-)

heehaw

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby heehaw » Thu Apr 07, 2016 12:19 pm

JPL wrote:I would like to see a picture of remote objects like this stripped of Milky Way stars, assuming it's possible to identify foreground stars. After a lifetime of viewing such pictures, it is difficult to escape the notion that space is cluttered with stars. Such a doctored image, if honestly labelled, might help dispel this misleading feeling of clutter, and in a sense convey more truthfully what is (isn't) out there.


I strongly endorse this suggestion. We all get conditioned by seeing the same thing over and over. Often a different perspective can usefully shake up our understanding of what we've seen so often. An example is McArthur's Universal Corrective Map of the World. Another example: I was in the audience decades ago with fellow astronomers trying to sell the idea of Hubble to an ignorant NASA Administrator, and Phil Morrison asked us all to picture in our minds the Andromeda Galaxy. (Do it yourself, right now!) Then Phil announced that we'd all got it completely wrong because of our human restricted perspective: he said "do it again, but this time picture it over a billion years: not only will you see it ROTATING, you will see HUGE NUMBERS OF SUPERNOVAE going off: it will look like a fourth of July pinwheel!" And of course, today, we'd also add, in our minds, the colossal Dark Matter! I like the doctored image suggestion!

heehaw

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby heehaw » Thu Apr 07, 2016 12:26 pm

Immediately after posting the above, I turned to http://epod.usra.edu/blog/ as I do each morning --- and found another example!
Try picturing in your mind a row of icicles. Then! go to ESPOD for a shock!

User avatar
Chris Peterson
Abominable Snowman
Posts: 13037
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby Chris Peterson » Thu Apr 07, 2016 12:29 pm

JPL wrote:I would like to see a picture of remote objects like this stripped of Milky Way stars, assuming it's possible to identify foreground stars. After a lifetime of viewing such pictures, it is difficult to escape the notion that space is cluttered with stars. Such a doctored image, if honestly labelled, might help dispel this misleading feeling of clutter, and in a sense convey more truthfully what is (isn't) out there.

Except near the edges of the galaxy, nearly every star in this image is a foreground star. Removing them would be a rather laborious manual task, however, and one complicated by the fact that many of the objects that appear to be stars are actually background galaxies.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Whiskybreath
Asternaut
Posts: 9
Joined: Thu Dec 17, 2015 1:27 pm

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby Whiskybreath » Thu Apr 07, 2016 1:38 pm

Also interesting is the 'J' shaped object halfway to the bottom of the picture from the centre.

User avatar
geckzilla
Ocular Digitator
Posts: 8517
Joined: Wed Sep 12, 2007 12:42 pm

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby geckzilla » Thu Apr 07, 2016 1:48 pm

Chris Peterson wrote:
geckzilla wrote:
dl martin, canada wrote:what is the red streak at the 6:30 position in the enlarged version?

I would guess an asteroid that was present during one of the observing sessions. If that's right, then the time between imaging was great enough that it was gone or not yet in the frame by the time the data used for the other two channels (green and blue) was collected.

Maybe, but usually asteroids show up as lines that are sequentially red, green, and blue. The isolated red line makes me think it was a more transient event like a meteor, present only during the red exposure.

There are a few more at the top, too. Could also be some odd artifact or dirt.
Just call me "geck" because "zilla" is like a last name.

User avatar
Chris Peterson
Abominable Snowman
Posts: 13037
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby Chris Peterson » Thu Apr 07, 2016 1:55 pm

geckzilla wrote:
Chris Peterson wrote:
geckzilla wrote:I would guess an asteroid that was present during one of the observing sessions. If that's right, then the time between imaging was great enough that it was gone or not yet in the frame by the time the data used for the other two channels (green and blue) was collected.

Maybe, but usually asteroids show up as lines that are sequentially red, green, and blue. The isolated red line makes me think it was a more transient event like a meteor, present only during the red exposure.

There are a few more at the top, too. Could also be some odd artifact or dirt.

Yeah. I wish there were more details about the shot. That would help in understanding the kind of artifacts we might reasonably expect.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
geckzilla
Ocular Digitator
Posts: 8517
Joined: Wed Sep 12, 2007 12:42 pm

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby geckzilla » Thu Apr 07, 2016 2:07 pm

Chris Peterson wrote:
JPL wrote:I would like to see a picture of remote objects like this stripped of Milky Way stars, assuming it's possible to identify foreground stars. After a lifetime of viewing such pictures, it is difficult to escape the notion that space is cluttered with stars. Such a doctored image, if honestly labelled, might help dispel this misleading feeling of clutter, and in a sense convey more truthfully what is (isn't) out there.

Except near the edges of the galaxy, nearly every star in this image is a foreground star. Removing them would be a rather laborious manual task, however, and one complicated by the fact that many of the objects that appear to be stars are actually background galaxies.

The halo of this galaxy likely extends to the edges of the frame, especially the left and right sides and more sparsely at the top and bottom. Separating the three main layers here would indeed be a strenuous exercise, but I think there may be fewer foreground stars than it looks like. IMO, the vast majority of tiny dots in this image are comprised of WLM and distant, blueish background galaxies. Obviously, I can't say for certain, but this view is well away from the plane of the Milky Way and it is also a relatively narrow field of view. I guess what I really want to say is that these dwarf galaxies are often more extended than one might initially think them to be.
Just call me "geck" because "zilla" is like a last name.

User avatar
Chris Peterson
Abominable Snowman
Posts: 13037
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby Chris Peterson » Thu Apr 07, 2016 2:22 pm

geckzilla wrote:
Chris Peterson wrote:
JPL wrote:I would like to see a picture of remote objects like this stripped of Milky Way stars, assuming it's possible to identify foreground stars. After a lifetime of viewing such pictures, it is difficult to escape the notion that space is cluttered with stars. Such a doctored image, if honestly labelled, might help dispel this misleading feeling of clutter, and in a sense convey more truthfully what is (isn't) out there.

Except near the edges of the galaxy, nearly every star in this image is a foreground star. Removing them would be a rather laborious manual task, however, and one complicated by the fact that many of the objects that appear to be stars are actually background galaxies.

The halo of this galaxy likely extends to the edges of the frame, especially the left and right sides and more sparsely at the top and bottom. Separating the three main layers here would indeed be a strenuous exercise, but I think there may be fewer foreground stars than it looks like. IMO, the vast majority of tiny dots in this image are comprised of WLM and distant, blueish background galaxies. Obviously, I can't say for certain, but this view is well away from the plane of the Milky Way and it is also a relatively narrow field of view. I guess what I really want to say is that these dwarf galaxies are often more extended than one might initially think them to be.

Yes, I thought about this and you might well be correct. It's not at all obvious at this scale where the galaxy's halo actually ends, or how compact the galaxy is.

Galaxies can largely be isolated automatically by looking at their profiles. A handful of obvious foreground stars can be removed on the basis of their intensity. But otherwise, this galaxy is too close to easily distinguish its stars from Milky Way stars by any easily measured characteristics. I think we could look at that area of sky in that region and statistically determine how many local stars should be present, however.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
neufer
Vacationer at Tralfamadore
Posts: 14075
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby neufer » Thu Apr 07, 2016 2:24 pm

Chris Peterson wrote:
geckzilla wrote:
Chris Peterson wrote:
Maybe, but usually asteroids show up as lines that are sequentially red, green, and blue. The isolated red line makes me think it was a more transient event like a meteor, present only during the red exposure.

There are a few more at the top, too. Could also be some odd artifact or dirt.

Yeah. I wish there were more details about the shot. That would help in understanding the kind of artifacts we might reasonably expect.
http://www.eso.org/observing/dfo/qualit ... k_QC1.html wrote:
<<The OmegaCAM dark template consists of three, one-hour exposures taken with the camera shutter closed. The processing consists of rejecting the cosmic ray events and subtracting the bias level. The remaining signal above the bias level is the dark signal, given in units of ADU/pixel/hour. For the reduction of subsequent on-sky observations the subtraction of the sky brightness will include the dark current, and a separation of both contributions is normally not required.>>
Art Neuendorffer

User avatar
Chris Peterson
Abominable Snowman
Posts: 13037
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby Chris Peterson » Thu Apr 07, 2016 2:32 pm

neufer wrote:
Chris Peterson wrote:Yeah. I wish there were more details about the shot. That would help in understanding the kind of artifacts we might reasonably expect.
http://www.eso.org/observing/dfo/qualit ... k_QC1.html wrote:
<<The OmegaCAM dark template consists of three, one-hour exposures taken with the camera shutter closed. The processing consists of rejecting the cosmic ray events and subtracting the bias level. The remaining signal above the bias level is the dark signal, given in units of ADU/pixel/hour. For the reduction of subsequent on-sky observations the subtraction of the sky brightness will include the dark current, and a separation of both contributions is normally not required.>>

Well, that still doesn't tell me much of anything about the details of today's image, or the subsequent processing. Things like filters, exposure times, and subexposure count (if any) would be very useful information.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
Coil_Smoke
Ensign
Posts: 83
Joined: Sun Nov 17, 2013 7:57 am

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby Coil_Smoke » Thu Apr 07, 2016 2:55 pm

Wow, That's a lot of real estate in that frame. I can't get over how many galaxies there are in the expanded{Double left click}version of this image...The definition of awesome . I am uncertain about the resolving power of these devices. At 3 million light years distance, are we seeing individual stars in WLM ?

User avatar
geckzilla
Ocular Digitator
Posts: 8517
Joined: Wed Sep 12, 2007 12:42 pm

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby geckzilla » Thu Apr 07, 2016 3:01 pm

Coil_Smoke wrote:At 3 million light years distance, are we seeing individual stars in WLM ?

Yeah, the brightest stars and stellar systems are indeed showing up as single points.
Just call me "geck" because "zilla" is like a last name.

User avatar
Fred the Cat
Theoretic Apothekitty
Posts: 357
Joined: Mon Feb 22, 2016 4:09 pm
AKA: Ron

Re: APOD: Wolf-Lundmark-Melotte (2016 Apr 07)

Postby Fred the Cat » Thu Apr 07, 2016 3:42 pm

You should probably know your neighborhood before venturing out into the wider cosmos. To do that in a great ride is even better. Now to get the best bang for your buck if you want to drive yourself.

Or you could just see them daily on APOD. Nice view of the neighbors!! :D
Feynman's Felicity "Only ascertain as a cat box survivor"


Return to “The Bridge: Discuss an Astronomy Picture of the Day”

Who is online

Users browsing this forum: No registered users and 0 guests