APOD: In Wolf's Cave (2019 Sep 07)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 3663
Joined: Fri Dec 04, 2009 3:27 am

APOD: In Wolf's Cave (2019 Sep 07)

Post by APOD Robot » Sat Sep 07, 2019 4:07 am

Image In Wolf's Cave

Explanation: The mysterious blue reflection nebula found in catalogs as VdB 152 or Ced 201 really is very faint. It lies at the tip of the long dark nebula Barnard 175 in a dusty complex that has also been called Wolf's Cave. At the center of this deep and widefield telescopic view, the cosmic apparitions are nearly 1,400 light-years away along the northern Milky Way in the royal constellation Cepheus. Near the edge of a large molecular cloud, pockets of interstellar dust in the region block light from background stars or scatter light from the embedded bright star giving the the nebula its characteristic blue color. Ultraviolet light from the star is also thought to cause a dim reddish luminescence in the nebular dust. Though stars do form in molecular clouds, this star seems to have only accidentally wandered into the area, as its measured velocity through space is very different from the cloud's velocity. Another dense, obscuring dark nebula, LDN 1221, is easy to spot at the upper right in the frame, while the more colorful planetary nebula Dengel-Hartl 5 is just below center. Faint reddish emission from an ancient supernova remnant can also be traced (lower right to upper left) against the dust-rich complex in Cepheus.

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

User avatar
Ann
4725 Å
Posts: 9734
Joined: Sat May 29, 2010 5:33 am

Re: APOD: In Wolf's Cave (2019 Sep 07)

Post by Ann » Sat Sep 07, 2019 8:19 am

This 527 KB image by T.A. Rector (University of Alaska Anchorage) and H. Schweiker (WIYN and NOAO/AURA/NSF) is a fine closeup of vdB 152. It also explains this part of the caption of the APOD:
APOD Robot wrote:

Ultraviolet light from the star is also thought to cause a dim reddish luminescence in the nebular dust.


The dim reddish luminescence in the nebular dust is not immediately obvious in the APOD. In the T. Rector/H. Schweiker image, most of the dusty structure looks decidedly yellowish, and a small red emission nebula is visible near top of it. This is is clearly a jet blown by a rambunctious baby star. We can also see that a pair of bright red elongated filaments near vdB 152 are part of the supernova remnant that can be seen in the APOD.

But when I looked at the APOD, I found myself smiling broadly when I spotted a lovely little pink arc with a dim but undeniably blue patch of luminosity inside it. I felt like starsurfer when I exclaimed triumphantly: Look, a planetary nebula!!! :D

Ann
Color Commentator

starsurfer
Stellar Cartographer
Posts: 3680
Joined: Thu Mar 15, 2012 7:25 pm

Re: APOD: In Wolf's Cave (2019 Sep 07)

Post by starsurfer » Sat Sep 07, 2019 10:30 am

Ann wrote:
Sat Sep 07, 2019 8:19 am
This 527 KB image by T.A. Rector (University of Alaska Anchorage) and H. Schweiker (WIYN and NOAO/AURA/NSF) is a fine closeup of vdB 152. It also explains this part of the caption of the APOD:
APOD Robot wrote:

Ultraviolet light from the star is also thought to cause a dim reddish luminescence in the nebular dust.


The dim reddish luminescence in the nebular dust is not immediately obvious in the APOD. In the T. Rector/H. Schweiker image, most of the dusty structure looks decidedly yellowish, and a small red emission nebula is visible near top of it. This is is clearly a jet blown by a rambunctious baby star. We can also see that a pair of bright red elongated filaments near vdB 152 are part of the supernova remnant that can be seen in the APOD.

But when I looked at the APOD, I found myself smiling broadly when I spotted a lovely little pink arc with a dim but undeniably blue patch of luminosity inside it. I felt like starsurfer when I exclaimed triumphantly: Look, a planetary nebula!!! :D

Ann
Actually DeHt 5 is a planetary nebula mimic, it is simply part of the interstellar medium being ionized by a white dwarf star. The previous PN classification is due to the presence of OIII emission. There are other examples of PN mimics such as Abell 35 or PHL 932 as well as who knows how many others.

User avatar
orin stepanek
Plutopian
Posts: 4973
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: In Wolf's Cave (2019 Sep 07)

Post by orin stepanek » Sat Sep 07, 2019 11:20 am

This is what caught my eye on today's AP{OD; I believe i've seen it before! :ssmile: Is that the 527 KB image Ann?
WolfsCaveCBMDMW1024.jpg
You do not have the required permissions to view the files attached to this post.
Orin

Smile today; tomorrow's another day!

BDanielMayfield
Don't bring me down
Posts: 2094
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: East Idaho

Re: APOD: In Wolf's Cave (2019 Sep 07)

Post by BDanielMayfield » Sat Sep 07, 2019 12:33 pm

orin stepanek wrote:
Sat Sep 07, 2019 11:20 am
This is what caught my eye on today's AP{OD; I believe i've seen it before! :ssmile: Is that the 527 KB image Ann?

WolfsCaveCBMDMW1024.jpg
A sock puppet?
"Happy are the peaceable ... "

Boomer12k
:---[===] *
Posts: 2569
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: In Wolf's Cave (2019 Sep 07)

Post by Boomer12k » Sat Sep 07, 2019 1:25 pm

A wondrous and dusty place...

:---[===] *

User avatar
Ann
4725 Å
Posts: 9734
Joined: Sat May 29, 2010 5:33 am

Re: APOD: In Wolf's Cave (2019 Sep 07)

Post by Ann » Sat Sep 07, 2019 3:03 pm

orin stepanek wrote:
Sat Sep 07, 2019 11:20 am
This is what caught my eye on today's AP{OD; I believe i've seen it before! :ssmile: Is that the 527 KB image Ann?

WolfsCaveCBMDMW1024.jpg
Not quite, but it is similar! :D

Ann
Color Commentator

User avatar
orin stepanek
Plutopian
Posts: 4973
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: In Wolf's Cave (2019 Sep 07)

Post by orin stepanek » Sat Sep 07, 2019 4:23 pm

BDanielMayfield wrote:
Sat Sep 07, 2019 12:33 pm
orin stepanek wrote:
Sat Sep 07, 2019 11:20 am
This is what caught my eye on today's AP{OD; I believe i've seen it before! :ssmile: Is that the 527 KB image Ann?

WolfsCaveCBMDMW1024.jpg
A sock puppet?
++! :lol2:
Orin

Smile today; tomorrow's another day!

BDanielMayfield
Don't bring me down
Posts: 2094
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: East Idaho

Re: APOD: In Wolf's Cave (2019 Sep 07)

Post by BDanielMayfield » Sat Sep 07, 2019 6:33 pm

orin stepanek wrote:
Sat Sep 07, 2019 4:23 pm
BDanielMayfield wrote:
Sat Sep 07, 2019 12:33 pm
orin stepanek wrote:
Sat Sep 07, 2019 11:20 am
This is what caught my eye on today's AP{OD; I believe i've seen it before! :ssmile: Is that the 527 KB image Ann?

WolfsCaveCBMDMW1024.jpg
A sock puppet?
++! :lol2:
But it couldn't be! Rule 12 at Starship Asterisk*:
Sock Puppetry

Users are allowed only one account per person. Do not register under a different username for any reason as that will be treated as sock puppetry. All such accounts (including the primary one) will be banned without warning. Should you feel a need to contact the moderator staff, use the Contact Us link at the bottom of the homepage.
"Happy are the peaceable ... "

User avatar
Ann
4725 Å
Posts: 9734
Joined: Sat May 29, 2010 5:33 am

Re: APOD: In Wolf's Cave (2019 Sep 07)

Post by Ann » Sat Sep 07, 2019 6:48 pm

BDanielMayfield wrote:
Sat Sep 07, 2019 6:33 pm
orin stepanek wrote:
Sat Sep 07, 2019 4:23 pm
BDanielMayfield wrote:
Sat Sep 07, 2019 12:33 pm

A sock puppet?
++! :lol2:
But it couldn't be! Rule 12 at Starship Asterisk*:
Sock Puppetry

Users are allowed only one account per person. Do not register under a different username for any reason as that will be treated as sock puppetry. All such accounts (including the primary one) will be banned without warning. Should you feel a need to contact the moderator staff, use the Contact Us link at the bottom of the homepage.

No Starship Asterisk* for Kermit the Frog? :( :cry:

Ann
Color Commentator

NCTom

Re: APOD: In Wolf's Cave (2019 Sep 07)

Post by NCTom » Sat Sep 07, 2019 7:58 pm

Again I say, I love this site! Kermit loves it too. He just cannot voice his opinions without croaking.

User avatar
neufer
Vacationer at Tralfamadore
Posts: 16217
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Henson's Voorwerp

Post by neufer » Sat Sep 07, 2019 10:02 pm

Ann wrote:
Sat Sep 07, 2019 6:48 pm

No Starship Asterisk* for Kermit the Frog? :( :cry:
https://en.wikipedia.org/wiki/Hanny%27s_Voorwerp wrote: <<Hanny's Voorwerp, (Dutch for Hanny's object) is a rare type of astronomical object called a quasar ionization echo. It was discovered in 2007 by Dutch schoolteacher Hanny van Arkel while she was participating as a volunteer in the Galaxy Zoo project, part of the Zooniverse group of citizen science websites. Photographically, it appears as a bright blob close to spiral galaxy IC 2497 in the constellation Leo Minor.

Hanny's Voorwerp (HsV) is about the size of a small galaxy and has a central hole over 16,000 light years across. In an image taken with the HST, HsV is colored green, a standard false color that is used to represent the presence of several luminous emission lines of glowing oxygen. HsV has been shown to be at the same distance from Earth as the adjacent galaxy IC 2497, which is about 650 million light-years away.

Star birth is occurring in the region of HsV that faces IC 2497. Radio observations indicate that this is due to an outflow of gas arising from the IC 2497's core which is interacting with a small region of HsV to collapse and form stars. The youngest of these stars are several million years old.

One hypothesis suggests that HsV consists of remnants of a small galaxy showing the impact of radiation from a bright quasar event that occurred in the center of IC 2497 about 100,000 years before how it is observed today. The quasar event is thought to have stimulated the bright emission that characterizes HsV. The quasar might have switched off in the last 200,000 years and is not visible in the available images. This might well be due to a process known as AGN feedback.

One possible explanation for the missing light-source is that illumination from the assumed quasar was a transient phenomenon. In this case, its effects on HsV would be still visible because of the distance of several tens of thousands of light years between HsV and the quasar in the nearby galaxy: HsV would show a "light echo" or "ghost image" of events that are older than those currently seen in the galaxy.

On 17 June 2010, a group of researchers at the European VLBI Network (EVN) and the UK’s Multi-Element Radio Linked Interferometer Network (MERLIN), proposed another related explanation. They hypothesized that the light comes from two sources:
  • (1) a supermassive black hole at the center of IC 2497, and
    (2) light produced by an interaction of an energetic jet from the black hole and the gas surrounding IC 2497.
In February 2012, W. C. Keel and others published a paper in the Monthly Notices of the Royal Astronomical Society. As a result of the interest in similar ionized clouds for the study of both the history and obscuration of Active Galactic Nucleus (AGN), participants in the Galaxy Zoo (GZ) project carried out a wide search for such clouds using data from the Sloan Digital Sky Survey (SDSS). This search yielded a list of 19 galaxies with AGN-photoionized clouds detected to beyond 10 kiloparsecs from the nuclei. These were nicknamed 'Voorwerpjes' from the Dutch for 'small objects'. In May 2015, W.C. Keel and others published a study in the Astrophysical Journal. This studies 8 of the original 19 Voorwerpjes in greater detail, focusing on 'the host-galaxy properties and origin of the gas.'>>
Last edited by neufer on Sun Sep 08, 2019 3:54 am, edited 1 time in total.
Art Neuendorffer

User avatar
orin stepanek
Plutopian
Posts: 4973
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: In Wolf's Cave (2019 Sep 07)

Post by orin stepanek » Sun Sep 08, 2019 12:07 am

BDanielMayfield wrote:
Sat Sep 07, 2019 6:33 pm
orin stepanek wrote:
Sat Sep 07, 2019 4:23 pm
BDanielMayfield wrote:
Sat Sep 07, 2019 12:33 pm

A sock puppet?
++! :lol2:
But it couldn't be! Rule 12 at Starship Asterisk*:
Sock Puppetry

Users are allowed only one account per person. Do not register under a different username for any reason as that will be treated as sock puppetry. All such accounts (including the primary one) will be banned without warning. Should you feel a need to contact the moderator staff, use the Contact Us link at the bottom of the homepage.
Guess I don't have to worry about that: 1 account is more than I can handle! :mrgreen:
Orin

Smile today; tomorrow's another day!

starsurfer
Stellar Cartographer
Posts: 3680
Joined: Thu Mar 15, 2012 7:25 pm

Re: APOD: In Wolf's Cave (2019 Sep 07)

Post by starsurfer » Mon Sep 09, 2019 12:43 pm

This paper might be of interest to some.