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

[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.

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[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...

:---[===] *

[joe25]

Does this 'object' have an NGC designation ?

[Ann]

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

[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.... )

[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.

[Nitpicker]

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.

[orin stepanek]

A very beautiful nebula! Indeed; it ranks with the top in my opinion!

[neufer]

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[Ann]

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

[neufer]

<<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.>>

<<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.>>

[bystander]

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[Deathfleer]

Oh, nearly thirty years already. Time flies.