APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 3327
Joined: Fri Dec 04, 2009 3:27 am

APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by APOD Robot » Thu Sep 20, 2018 4:11 am

Image Stars and Dust in Corona Australis

Explanation: Cosmic dust clouds and young, energetic stars inhabit this telescopic vista, less than 500 light-years away toward the northern boundary of Corona Australis, the Southern Crown. The dust clouds effectively block light from more distant background stars in the Milky Way. But the striking complex of reflection nebulae cataloged as NGC 6726, 6727, and IC 4812 produce a characteristic color as blue light from the region's young, hot stars is reflected by the cosmic dust. The dust also obscures from view stars still in the process of formation. At top right, smaller yellowish nebula NGC 6729 bends around young variable star R Coronae Australis. Near it, glowing arcs and loops shocked by outflows from embedded newborn stars are identified as Herbig-Haro objects. On the sky this field of view spans about 1 degree. That corresponds to almost 9 light-years at the estimated distance of the nearby star forming region.

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

User avatar
Ann
4725 Å
Posts: 9048
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by Ann » Thu Sep 20, 2018 4:33 am

APOD Robot wrote:
At top right, smaller yellowish nebula NGC 6729 bends around young variable star R Coronae Australis.
I can see no yellowish nebula in today's APOD. But the little pink (and deeper red) tendrils and arcs are beautiful in this "sea of blue"! :D

Ann
Last edited by Ann on Thu Sep 20, 2018 7:12 am, edited 1 time in total.
Color Commentator

User avatar
geckzilla
Ocular Digitator
Posts: 8886
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by geckzilla » Thu Sep 20, 2018 5:00 am

Ann wrote:
Thu Sep 20, 2018 4:33 am
APOD Robot wrote:
At top right, smaller yellowish nebula NGC 6729 bends around young variable star R Coronae Australis.
I can see no yellowish nebula in today's APOD. But the little pink (and deeper red) tendrils and arcs) are beautiful in this "sea of blue"! :D

Ann
Note that it does look indistinguishable from yellow to a colorblind individual.
Just call me "geck" because "zilla" is like a last name.

User avatar
bystander
Apathetic Retiree
Posts: 17520
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by bystander » Thu Sep 20, 2018 5:25 am

geckzilla wrote:
Thu Sep 20, 2018 5:00 am
Ann wrote:
Thu Sep 20, 2018 4:33 am
APOD Robot wrote:
At top right, smaller yellowish nebula NGC 6729 bends around young variable star R Coronae Australis.
I can see no yellowish nebula in today's APOD. But the little pink (and deeper red) tendrils and arcs) are beautiful in this "sea of blue"! :D

Ann
Note that it does look indistinguishable from yellow to a colorblind individual.
A version of this explanation has been used with several different images before. At least they corrected "At the left" to "At top right".
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

User avatar
Ann
4725 Å
Posts: 9048
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by Ann » Thu Sep 20, 2018 7:10 am

There actually is a lttle nebula between the main blue "clouds" that is shaped like an arc curving round a star, and the bottom left part of that arc is yellowish. More precisely, it is a bit orange.

Ann
Color Commentator

NHcycler

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by NHcycler » Thu Sep 20, 2018 10:26 am

I wonder what caused that gaping hole in the lower left half of the cloud? Also, what a beautiful face-on spiral background galaxy at the far left of the photo!

User avatar
Ann
4725 Å
Posts: 9048
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by Ann » Thu Sep 20, 2018 10:54 am

NHcycler wrote:
Thu Sep 20, 2018 10:26 am
I wonder what caused that gaping hole in the lower left half of the cloud? Also, what a beautiful face-on spiral background galaxy at the far left of the photo!
Gorgeous spiral indeed. It has no bar and its bulge is fairly big. Its arms are moderately tightly wound, but one outer arm is rather widely separated from the main "body" of the galaxy. I'd say it is a spiral galaxy of Hubble class Sab or Sb (like Andromeda).

What about the gaping hole in one of the blue clouds? My amateur guess is that one of the two components of the prominent double star which is lighting up the blue cloud on the left had an outburst of some kind a while ago, and emitted a jet which blew a hole in the glowing nebula.

Ann
Color Commentator

User avatar
neufer
Vacationer at Tralfamadore
Posts: 15337
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by neufer » Thu Sep 20, 2018 12:15 pm

https://en.wikipedia.org/wiki/NGC_6729 wrote:


<<This very detailed false-colour image from ESO’s Very Large Telescope shows the dramatic effects of very young stars on the dust and gas from which they were born in the star-forming region NGC 6729. This fan-shaped nebula opens from the star R Coronae Australis toward the star T CrA to the south-east. R CrA is a pre-main-sequence star in the Corona Australis molecular complex, one of the closer star-forming regions of the galaxy at a distance of 130 pc. The baby stars are invisible in this picture, being hidden behind dust clouds at the upper left of the picture, but material they are ejecting is crashing into the surroundings at speeds of that can be as high as one million kilometres per hour. This picture was taken by the FORS1 instrument and records the scene in the light of glowing hydrogen and sulphur.>>
Art Neuendorffer

Wallybru

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by Wallybru » Thu Sep 20, 2018 1:01 pm

Why does there appear to be two stars?

BDanielMayfield
Don't bring me down
Posts: 1747
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: East Idaho

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by BDanielMayfield » Thu Sep 20, 2018 2:14 pm

Wallybru wrote:
Thu Sep 20, 2018 1:01 pm
Why does there appear to be two stars?
Because there are (at least) two stars. Most stars are part of multiple systems. And add to that the random chance alignments with background stars and we find that double stars are very common.

Bruce
"Happy are the peaceable ... "

User avatar
neufer
Vacationer at Tralfamadore
Posts: 15337
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by neufer » Thu Sep 20, 2018 5:21 pm

BDanielMayfield wrote:
Thu Sep 20, 2018 2:14 pm
Wallybru wrote:
Thu Sep 20, 2018 1:01 pm

Why does there appear to be two stars?
Because there are (at least) two stars. Most stars are part of multiple systems. And add to that the random chance alignments with background stars and we find that double stars are very common.
https://en.wikipedia.org/wiki/Coronet_cluster wrote:
<<The Coronet cluster, also known as the R CrA cluster after its best-known member, is a small open cluster located about 170 parsecs away in the southern constellation Corona Australis. Isolated [Long.: 0, Lat.: -18] at the edge of the Gould Belt the Coronet cluster is 3.5 times closer to the Earth than the Orion Nebula Cluster. The cluster center is composed of mostly [0.5-2 million year old] young stars.>>
https://en.wikipedia.org/wiki/Gould_Belt wrote: The Gould Belt is a partial ring of stars in the Milky Way, about 3000 light years across, tilted toward the galactic plane by about 16 to 20 degrees. It contains many O- and B-type stars, and may represent the local spiral arm to which the Sun belongs—currently the Sun is about 325 light years from the arm's center. The belt is thought to be from 30 to 50 million years old, and of unknown origin. It is named after Benjamin Gould, who identified it in 1879.

The belt contains bright stars in many constellations including (in order going more or less eastward) Cepheus, Lacerta, Perseus, Orion, Canis Major, Puppis, Vela, Carina, Crux (the Southern Cross), Centaurus, Lupus, and Scorpius (including the Scorpius-Centaurus Association). The Milky Way visible in the sky also passes through most of these constellations, but a bit southeast of Lupus.

Star-forming regions and OB associations that make up this region include the Orion Nebula and the Orion molecular clouds, the Scorpius-Centaurus OB Association, Cepheus OB2, Perseus OB2, and the Taurus-Auriga Molecular Clouds. The Serpens Molecular Cloud containing star-forming regions W40 and Serpens south is often included in Gould Belt surveys, but is not formally part of the Gould Belt due to its greater distance.

A theory proposed around 2009 suggests that the Gould Belt formed about 30 million years ago when a blob of dark matter collided with the molecular cloud in our region. There is also evidence for similar Gould belts in other galaxies.>>
Last edited by neufer on Thu Sep 20, 2018 7:17 pm, edited 1 time in total.
Art Neuendorffer

User avatar
Ann
4725 Å
Posts: 9048
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by Ann » Thu Sep 20, 2018 6:55 pm

NGC 6726, 6727 and R Corona Australis.
Photo: Rolf Olsen.
In the beautiful picture by Rolf Olsen at left, NGC 6729 (the nebula surrounding R Corona Australis) looks peach-colored rather than pink. The nebula is likely dust-reddened, so there is a reddish and a turquoise component from Hα and Hβ emission as well as whitish light from the star itself, but the nebula is dust-reddened into a peach or slightly orange hue.

The Flame Nebula with Orion's Belt, the Horsehead Nebula and the Orion Nebula.
Photo: Terry Hancock.














The R Corona Australis Nebula may be slightly similar to the Flame Nebula in Orion. In the picture at right, the Flame Nebula can be seen as a tiny yellowish and darkly bisected patch at lower left. The yellow color is due to severe dust-reddening of the reddish and a turquoise Hα and Hβ emission from young stars and the whitish starlight from the embedded stars themselves.

But the Flame Nebula does not look yellow in all pictures. It looks quite pink in this picture by David Murray. But it looks very yellow indeed in this picture by Don Taylor Imagery.

So nebulas like the R Corona Australis Nebula and the Flame Nebula may look either pink or yellow, depending on the filters used for the image and the processing.

Ann
Color Commentator

User avatar
MarkBour
Subtle Signal
Posts: 739
Joined: Mon Aug 26, 2013 2:44 pm
Location: Illinois, USA

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by MarkBour » Thu Sep 20, 2018 8:32 pm

bystander wrote:
Thu Sep 20, 2018 5:25 am
geckzilla wrote:
Thu Sep 20, 2018 5:00 am
Ann wrote:
Thu Sep 20, 2018 4:33 am
I can see no yellowish nebula in today's APOD. But the little pink (and deeper red) tendrils and arcs) are beautiful in this "sea of blue"! :D
Ann
Note that it does look indistinguishable from yellow to a colorblind individual.
A version of this explanation has been used with several different images before. At least they corrected "At the left" to "At top right".
Note that "at the left" is indistinguishable from "at top right" to a blind individual. :-)
Mark Goldfain

User avatar
neufer
Vacationer at Tralfamadore
Posts: 15337
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by neufer » Thu Sep 20, 2018 9:02 pm

MarkBour wrote:
Thu Sep 20, 2018 8:32 pm

Note that "at the left" is indistinguishable from "at top right" to a blind individual. :-)
So...you can't teach a blind person the difference between left & right :?:
Art Neuendorffer

User avatar
geckzilla
Ocular Digitator
Posts: 8886
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by geckzilla » Fri Sep 21, 2018 5:57 am

I have long suspected one or both APOD editors to be colorblind in some way, and I am aware that descriptions are sometimes reused. Think for a moment: If you were colorblind, you wouldn't know that the color of the nebula was red in one picture and yellow in another. So then you'd change the location, but not necessarily the color description. I'm aware that I could be wrong, also. I'd just ask, but wouldn't that ruin the fun?
Just call me "geck" because "zilla" is like a last name.

User avatar
neufer
Vacationer at Tralfamadore
Posts: 15337
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by neufer » Fri Sep 21, 2018 1:29 pm

geckzilla wrote:
Fri Sep 21, 2018 5:57 am

I have long suspected one or both APOD editors to be colorblind in some way, and I am aware that descriptions are sometimes reused. Think for a moment: If you were colorblind, you wouldn't know that the color of the nebula was red in one picture and yellow in another. So then you'd change the location, but not necessarily the color description. I'm aware that I could be wrong, also. I'd just ask, but wouldn't that ruin the fun?
https://en.wikipedia.org/wiki/Color_blindness wrote:
<<Most color-blind individuals are anomanous anomalous trichromats. The first scientific paper on the subject of color blindness, Extraordinary facts relating to the vision of colours, was published by the English chemist, physicist, and meteorologist John Dalton in 1798 after the realization of his own color blindness. Because of Dalton's work, the general condition has been called daltonism.>>
Art Neuendorffer

starsurfer
Stellar Cartographer
Posts: 3249
Joined: Thu Mar 15, 2012 7:25 pm

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by starsurfer » Fri Sep 21, 2018 4:25 pm

This image would look better if it was north up. :lol2:

User avatar
MarkBour
Subtle Signal
Posts: 739
Joined: Mon Aug 26, 2013 2:44 pm
Location: Illinois, USA

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by MarkBour » Mon Sep 24, 2018 8:17 pm

neufer wrote:
Thu Sep 20, 2018 9:02 pm
MarkBour wrote:
Thu Sep 20, 2018 8:32 pm

Note that "at the left" is indistinguishable from "at top right" to a blind individual. :-)
So...you can't teach a blind person the difference between left & right :?:
Sorry, my only use here was in the context of looking at an APOD image and whether or not a caption should be adjusted.
... and was meant to be absurd.
... That caption is fine. After all, a person who only speaks Nepali can't read it anyway.
Mark Goldfain

User avatar
neufer
Vacationer at Tralfamadore
Posts: 15337
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by neufer » Mon Sep 24, 2018 10:17 pm

MarkBour wrote:
Mon Sep 24, 2018 8:17 pm
neufer wrote:
Thu Sep 20, 2018 9:02 pm
MarkBour wrote:
Thu Sep 20, 2018 8:32 pm

Note that "at the left" is indistinguishable from "at top right" to a blind individual. :-)
So...you can't teach a blind person the difference between left & right :?:
Sorry, my only use here was in the context of looking at an APOD image and whether or not a caption should be adjusted.
... and was meant to be absurd.
https://www.etymonline.com/word/absurd#etymonline_v_25932 wrote:
<<absurd (adj.) "plainly illogical," 1550s, from Middle French absurde (16c.), from Latin absurdus "out of tune, discordant;" figuratively "incongruous, foolish, silly, senseless," from ab- "off, away from," here perhaps an intensive prefix, + surdus "dull, deaf, mute," which is possibly from an imitative PIE root meaning "to buzz, whisper" (see susurration). Thus the basic sense is perhaps "out of tune," but de Vaan writes, "Since 'deaf' often has two semantic sides, viz. 'who cannot hear' and 'who is not heard,' ab-surdus can be explained as 'which is unheard of' ...">>
Art Neuendorffer

User avatar
MarkBour
Subtle Signal
Posts: 739
Joined: Mon Aug 26, 2013 2:44 pm
Location: Illinois, USA

Re: APOD: Stars and Dust in Corona Australis (2018 Sep 20)

Post by MarkBour » Tue Sep 25, 2018 3:14 pm

geckzilla wrote:
Fri Sep 21, 2018 5:57 am
I have long suspected one or both APOD editors to be colorblind in some way, and I am aware that descriptions are sometimes reused. Think for a moment: If you were colorblind, you wouldn't know that the color of the nebula was red in one picture and yellow in another. So then you'd change the location, but not necessarily the color description. I'm aware that I could be wrong, also. I'd just ask, but wouldn't that ruin the fun?
Ah.
Mark Goldfain