APOD: The Shape of the Southern Crab (2019 Apr 24)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 4477
Joined: Fri Dec 04, 2009 3:27 am

APOD: The Shape of the Southern Crab (2019 Apr 24)

Post by APOD Robot » Wed Apr 24, 2019 4:10 am

Image The Shape of the Southern Crab

Explanation: The symmetric, multi-legged appearance of the Southern Crab Nebula is certainly distinctive. About 7,000 light-years distant toward the southern sky constellation Centaurus, its glowing nested hourglass shapes are produced by the remarkable symbiotic binary star system at its center. The nebula's dramatic stellar duo consists of a hot white dwarf star and cool, pulsating red giant star shedding outer layers that fall onto the smaller, much hotter companion. Embedded in a disk of material, outbursts from the white dwarf cause an outflow of gas driven away both above and below the disk resulting in the bipolar hourglass shapes. The bright central shape is about half a light-year across. This new Hubble Space Telescope image celebrates the 29th anniversary of Hubble's launch on April 24, 1990 on board the Space Shuttle Discovery.

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

Boomer12k
:---[===] *
Posts: 2691
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: The Shape of the Southern Crab (2019 Apr 24)

Post by Boomer12k » Wed Apr 24, 2019 8:21 am

to me it looks like an ant, or spider, or such, but fine...

Awww.... it has Bipolar Disorder....I wonder if it will go Type 1a on us....

My own symptoms began with "Explosive Anger" too...

Lovely nebula...great shot...

:---[===] *

joe25

Re: APOD: The Shape of the Southern Crab (2019 Apr 24)

Post by joe25 » Wed Apr 24, 2019 9:57 am

Does this 'object' have an NGC designation ?

User avatar
Ann
4725 Å
Posts: 11650
Joined: Sat May 29, 2010 5:33 am

Re: APOD: The Shape of the Southern Crab (2019 Apr 24)

Post by Ann » Wed Apr 24, 2019 10:17 am

joe25 wrote:
Wed Apr 24, 2019 9:57 am
Does this 'object' have an NGC designation ?
I guess not.
Wikipedia wrote about the Southern Crab Nebula:

Designations: V852 Cen, Hen 2-104, IRAS 14085-5112, PN G315.4+09.4, Wray 16-147, 2MASS J14115206-5126241

Apparent magnitude (V): 14.20
The Southern Crab Nebula is a 14th magnitude object. I don't think NGC lists objects that are generally fainter than, say, 12th magnitude.

Compare the Southern Crab Nebula with the "real" Crab Nebula, Messier 1. According to Wikipedia, the Crab Nebula is an 8th magnitude object. A faint 8th magnitude object, admittedly, but the Crab is still almost six magnitudes brighter than the Southern Crab. That's a lot.

Interestingly, the Crab and the Southern Crab appear to be at comparable distances from us, so the fact that the Crab Nebula is almost six magnitudes brighter than its southern "cousin" says something about the relative brightness of these two objects.

Ann
Color Commentator

User avatar
Indigo_Sunrise
Science Officer
Posts: 438
Joined: Fri Jul 15, 2005 1:40 pm
Location: Md

Re: APOD: The Shape of the Southern Crab (2019 Apr 24)

Post by Indigo_Sunrise » Wed Apr 24, 2019 10:48 am

Very interesting image. One question: what does this sentence,
The nebula's dramatic stellar duo consists of a hot white dwarf star and cool, pulsating red giant star shedding outer layers that fall onto the smaller, much hotter companion.
mean? Do both of the stars in the binary system shed layers that fall back onto the smaller of the two stars? Or is there another star that receives these shed layers? (It's just a bit confusing to me.... :( )
Forget the box, just get outside.

NCTom

Re: APOD: The Shape of the Southern Crab (2019 Apr 24)

Post by NCTom » Wed Apr 24, 2019 11:40 am

Has the estimated distance between the two stars, red giant and white dwarf, been recorded? I couldn't find it through the links and it appears wiki doesn't report it.

User avatar
Nitpicker
Inverse Square
Posts: 2692
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: The Shape of the Southern Crab (2019 Apr 24)

Post by Nitpicker » Wed Apr 24, 2019 11:57 am

Ann wrote:
Wed Apr 24, 2019 10:17 am
joe25 wrote:
Wed Apr 24, 2019 9:57 am
Does this 'object' have an NGC designation ?
I guess not.
Wikipedia wrote about the Southern Crab Nebula:

Designations: V852 Cen, Hen 2-104, IRAS 14085-5112, PN G315.4+09.4, Wray 16-147, 2MASS J14115206-5126241

Apparent magnitude (V): 14.20
The Southern Crab Nebula is a 14th magnitude object. I don't think NGC lists objects that are generally fainter than, say, 12th magnitude.

Compare the Southern Crab Nebula with the "real" Crab Nebula, Messier 1. According to Wikipedia, the Crab Nebula is an 8th magnitude object. A faint 8th magnitude object, admittedly, but the Crab is still almost six magnitudes brighter than the Southern Crab. That's a lot.

Interestingly, the Crab and the Southern Crab appear to be at comparable distances from us, so the fact that the Crab Nebula is almost six magnitudes brighter than its southern "cousin" says something about the relative brightness of these two objects.

Ann
The angular size of the southern crab is roughly five times smaller, I think. So the difference in surface brightness would not be as great as the magnitude difference suggests, when compared with the northern crab. But I haven't done the sums.

User avatar
orin stepanek
Plutopian
Posts: 6986
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: The Shape of the Southern Crab (2019 Apr 24)

Post by orin stepanek » Wed Apr 24, 2019 12:04 pm

A very beautiful nebula! Indeed; it ranks with the top in my opinion! :clap: :thumb_up: :yes:
Orin

Smile today; tomorrow's another day!

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18560
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Snot from jet

Post by neufer » Wed Apr 24, 2019 12:20 pm



Art Neuendorffer

User avatar
Ann
4725 Å
Posts: 11650
Joined: Sat May 29, 2010 5:33 am

Re: APOD: The Shape of the Southern Crab (2019 Apr 24)

Post by Ann » Wed Apr 24, 2019 2:43 pm

Nitpicker wrote:
Wed Apr 24, 2019 11:57 am
Ann wrote:
Wed Apr 24, 2019 10:17 am
joe25 wrote:
Wed Apr 24, 2019 9:57 am
Does this 'object' have an NGC designation ?
I guess not.
Wikipedia wrote about the Southern Crab Nebula:

Designations: V852 Cen, Hen 2-104, IRAS 14085-5112, PN G315.4+09.4, Wray 16-147, 2MASS J14115206-5126241

Apparent magnitude (V): 14.20
The Southern Crab Nebula is a 14th magnitude object. I don't think NGC lists objects that are generally fainter than, say, 12th magnitude.

Compare the Southern Crab Nebula with the "real" Crab Nebula, Messier 1. According to Wikipedia, the Crab Nebula is an 8th magnitude object. A faint 8th magnitude object, admittedly, but the Crab is still almost six magnitudes brighter than the Southern Crab. That's a lot.

Interestingly, the Crab and the Southern Crab appear to be at comparable distances from us, so the fact that the Crab Nebula is almost six magnitudes brighter than its southern "cousin" says something about the relative brightness of these two objects.

Ann
The angular size of the southern crab is roughly five times smaller, I think. So the difference in surface brightness would not be as great as the magnitude difference suggests, when compared with the northern crab. But I haven't done the sums.
I'm sure you're right, Nit. But that just proves that the small Southern Crab doesn't compensate for its small size by sporting a higher surface brightness, the way the small Orion Nebula does compared with the large but faint Rosette Nebula.

So the Crab pumps out a lot more power than the Southern Crab. Then again, the Southern Crab hasn't gone supernova yet, but the Crab Nebula's pulsar engine - or its progenitor - has.

Ann
Color Commentator

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18560
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

A century too late.

Post by neufer » Wed Apr 24, 2019 3:59 pm

https://www.spacetelescope.org/news/heic1907/ wrote:
<<The Southern Crab Nebula was first written about in 1967, but was assumed to be an ordinary star until 1989, when it was observed using telescopes at the European Southern Observatory’s La Silla Observatory.>>
https://en.wikipedia.org/wiki/New_General_Catalogue wrote:
<<The New General Catalogue of Nebulae and Clusters of Stars (abbreviated as NGC) is a catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. It expands upon the cataloguing work of William and Caroline Herschel, and John Herschel's General Catalogue of Nebulae and Clusters of Stars. The NGC contains 7,840 objects, known as the NGC objects. It includes all types of deep space objects, including galaxies, star clusters, emission nebulae and absorption nebulae. Dreyer also published two supplements to the NGC in 1895 and 1908, known as the Index Catalogues, describing a further 5,386 astronomical objects.

Objects in the sky of the southern hemisphere are catalogued somewhat less thoroughly, but many were observed by John Herschel or James Dunlop. The NGC had many errors, but an attempt to eliminate them was initiated by the NGC/IC Project in 1993, after partial attempts with the Revised New General Catalogue (RNGC) by Jack W. Sulentic and William G. Tifft in 1973, and NGC2000.0 by Roger W. Sinnott in 1988.

The Revised New General Catalogue and Index Catalogue (abbreviated as RNGC/IC) was compiled in 2009 by Wolfgang Steinicke.>>
Art Neuendorffer

User avatar
bystander
Apathetic Retiree
Posts: 20807
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Re: APOD: The Shape of the Southern Crab (2019 Apr 24)

Post by bystander » Wed Apr 24, 2019 5:08 pm

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

Deathfleer

Re: APOD: The Shape of the Southern Crab (2019 Apr 24)

Post by Deathfleer » Thu Apr 25, 2019 3:07 am

Oh, nearly thirty years already. Time flies.