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APOD: The Shape of the Southern Crab (2019 Apr 24)
Posted: Wed Apr 24, 2019 4:10 am
by APOD Robot
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.
Re: APOD: The Shape of the Southern Crab (2019 Apr 24)
Posted: Wed Apr 24, 2019 8:21 am
by Boomer12k
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...
:---[===] *
Re: APOD: The Shape of the Southern Crab (2019 Apr 24)
Posted: Wed Apr 24, 2019 9:57 am
by joe25
Does this 'object' have an NGC designation ?
Re: APOD: The Shape of the Southern Crab (2019 Apr 24)
Posted: Wed Apr 24, 2019 10:17 am
by Ann
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
Re: APOD: The Shape of the Southern Crab (2019 Apr 24)
Posted: Wed Apr 24, 2019 10:48 am
by Indigo_Sunrise
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....
![Sad :(](./images/smilies/icon_sad.gif)
)
Re: APOD: The Shape of the Southern Crab (2019 Apr 24)
Posted: Wed Apr 24, 2019 11:40 am
by NCTom
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.
Re: APOD: The Shape of the Southern Crab (2019 Apr 24)
Posted: Wed Apr 24, 2019 11:57 am
by Nitpicker
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.
Re: APOD: The Shape of the Southern Crab (2019 Apr 24)
Posted: Wed Apr 24, 2019 12:04 pm
by orin stepanek
Snot from jet
Posted: Wed Apr 24, 2019 12:20 pm
by neufer
Re: APOD: The Shape of the Southern Crab (2019 Apr 24)
Posted: Wed Apr 24, 2019 2:43 pm
by Ann
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
A century too late.
Posted: Wed Apr 24, 2019 3:59 pm
by neufer
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.>>
Re: APOD: The Shape of the Southern Crab (2019 Apr 24)
Posted: Wed Apr 24, 2019 5:08 pm
by bystander
Re: APOD: The Shape of the Southern Crab (2019 Apr 24)
Posted: Thu Apr 25, 2019 3:07 am
by Deathfleer
Oh, nearly thirty years already. Time flies.