APOD: Stars and Dust Across Corona Australis (2013 Sep 12)

Comments and questions about the APOD on the main view screen.

APOD: Stars and Dust Across Corona Australis (2013 Sep 12)

Postby APOD Robot » Thu Sep 12, 2013 4:07 am

Image Stars and Dust Across Corona Australis

Explanation: Cosmic dust clouds sprawl across a rich field of stars in this sweeping telescopic vista near the northern boundary of Corona Australis, the Southern Crown. Less than 500 light-years away the dust clouds effectively block light from more distant background stars in the Milky Way. The entire frame spans about 2 degrees or over 15 light-years at the clouds' estimated distance. Near center is a group of lovely reflection nebulae cataloged as NGC 6726, 6727, 6729, and IC 4812. A characteristic blue color is produced as light from hot stars is reflected by the cosmic dust. The dust also obscures from view stars in the region still in the process of formation. Smaller yellowish nebula NGC 6729 surrounds young variable star R Coronae Australis. Below it are arcs and loops identified as Herbig Haro objects associated with energetic newborn stars. Magnificent globular star cluster NGC 6723 is at the right. Though NGC 6723 appears to be part of the group, its ancient stars actually lie nearly 30,000 light-years away, far beyond the young stars of the Corona Australis dust clouds.

<< Previous APOD This Day in APOD Next APOD >>
User avatar
APOD Robot
Otto Posterman
 
Posts: 1866
Joined: Fri Dec 04, 2009 3:27 am

Re: APOD: Stars and Dust Across Corona Australis (2013 Sep 1

Postby Ann » Thu Sep 12, 2013 4:49 am

This is a fascinating part of the sky, and it is a lovely picture.

Ann
Color Commentator
User avatar
Ann
4725 Å
 
Posts: 5796
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Stars and Dust Across Corona Australis (2013 Sep 1

Postby Boomer12k » Thu Sep 12, 2013 8:58 am

The dust looks like a fish, with the "EYE" to the left of the nebulae...swimming in the eternal "sea" of space....awesome shot...the Globular Cluster is fantastic.

Now where did I put my broom and dust pan???

:---[===] *
Boomer12k
:---[===] *
 
Posts: 1119
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: Stars and Dust Across Corona Australis (2013 Sep 1

Postby neufer » Thu Sep 12, 2013 10:59 am

Art Neuendorffer
User avatar
neufer
Vacationer at Tralfamadore
 
Posts: 11631
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Stars and Dust Across Corona Australis (2013 Sep 1

Postby robolt » Fri Sep 13, 2013 3:18 am

What comprises the dust? Is it elemental material or truly "dust" in the sense of particulate matter?
robolt
 

Re: APOD: Stars and Dust Across Corona Australis (2013 Sep 1

Postby neufer » Fri Sep 13, 2013 3:42 am

robolt wrote:
What comprises the dust? Is it elemental material or truly "dust" in the sense of particulate matter?
http://en.wikipedia.org/wiki/Cosmic_dust wrote:

Click to play embedded YouTube video.

<<Stardust grains (also called presolar grains by meteoriticists) are contained within meteorites, from which they are extracted in terrestrial laboratories. The meteorites have stored those stardust grains ever since the meteorites first assembled within the planetary accretion disk more than four billion years ago. So-called carbonaceous chondrites are especially fertile reservoirs of stardust. Each stardust grain existed before the earth was formed. Stardust is a scientific term; not just a poetic one, referring to refractory dust grains that condensed from cooling ejected gases from individual presolar stars and mixed into the cloud from which the solar system condensed.

Many different types of stardust have been identified by laboratory measurements of the highly unusual isotopic composition of the chemical elements that comprise each stardust grain. These refractory mineral grains may earlier have been coated with volatile compounds, but those are lost in the dissolving of meteorite matter in acids, leaving only insoluble refractory minerals. Finding the grain cores without dissolving most of the meteorite has been possible, but difficult and labor intensive.

Many new aspects of nucleosynthesis have been discovered from the isotopic ratios within the stardust grains. An important property of stardust is the hard, refractory, high-temperature nature of the grains. Prominent are silicon carbide, graphite, aluminium oxide, aluminium spinel, and other such grains that would condense at high temperature from a cooling gas, such as in stellar winds or in the decompression of the inside of a supernova. They differ greatly from the solids formed at low temperature within the interstellar medium.

Also important are their extreme isotopic compositions, which are expected to exist nowhere in the interstellar medium. This also suggests that the stardust condensed from the gases of individual stars before the isotopes could be diluted by mixing with the interstellar medium. These allow the source stars to be identified. For example, the heavy elements within the SiC grains are almost pure S-process isotopes, fitting their condensation within AGB star red giant winds inasmuch as the AGB stars are the main source of S-process nucleosynthesis and have atmospheres observed by astronomers to be highly enriched in dredged-up s process elements. Another dramatic example comes from the supernova condensates, usually shortened by acronym to SUNOCON to distinguish them from other stardust condensed within stellar atmospheres. SUNOCONs contain in their calcium an excessively large abundance of 44Ca, demonstrating that they condensed containing abundant radioactive 44Ti, which has a 65 year half-life. It was thus still alive when the SUNOCON condensed within the expanding supernova interior but would have been extinct after the time required for mixing with the interstellar gas. Its discovery proved the prediction from 1975 to identify SUNOCONs in this way. But SiC SUNOCONs are only about 1% as numerous as are SiC stardust from AGB stars.

Stardust is but a modest fraction of the condensed cosmic dust, forming less than 0.1% of the mass of total interstellar solids. The high interest in stardust derives from new information that it has brought to the sciences of stellar evolution and nucleosynthesis. A fascinating aspect to human culture is the study within terrestrial laboratories of solids that existed before the earth existed. This was once thought impossible, especially in the decades when cosmochemists were confident that the solar system began as a hot gas virtually devoid of any remaining solids, which would have been vaporized by high temperature. The very existence of stardust shows that this historic picture was incorrect.>>
Art Neuendorffer
User avatar
neufer
Vacationer at Tralfamadore
 
Posts: 11631
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Stars and Dust Across Corona Australis (2013 Sep 1

Postby DavidLeodis » Fri Sep 13, 2013 7:18 pm

The blue feature reminds me of the face mask in the Scream movies. :) Mind you, if you do scream I understand that nobody will hear you in space!
User avatar
DavidLeodis
Perceptatron
 
Posts: 826
Joined: Mon May 01, 2006 1:00 pm


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

Who is online

Users browsing this forum: Google [Bot] and 4 guests