Southern Crab Nebula

{{Short description|Planetary nebula in the constellation Centaurus}}

{{Infobox nebula

|name = Southern Crab Nebula

|image = 260px

|caption = The Southern Crab Nebula image taken by Hubble{{cite web |title=Hubble Celebrates its 29th Birthday with Unrivaled View of the Southern Crab Nebula |url=https://www.spacetelescope.org/news/heic1907/ |website=www.spacetelescope.org |access-date=18 April 2019 }}

|credit = ESA, NASA, and STScI

|type = planetary

|epoch = J2000

|subtype =

|class =

|ra = {{RA|14|11|52.06}}{{cite simbad|title=Hen 2-104}}

|dec = {{DEC|-51|26|24.1}}

|dist_ly = {{convert|7000|ly|pc|abbr=on|lk=on}}{{cite web|title=The Southern Crab Nebula, a planetary nebula in Centaurus|url=http://annesastronomynews.com/photo-gallery-ii/nebulae-clouds/the-southern-crab-nebula-he2-104/|work=Anne's Astronomy News|date=18 November 2012 |access-date=22 January 2017}}

|appmag_v = 14.20

|appdia =

|size_v =

|constellation = Centaurus

|radius_ly =

|radius_pc =

|dimensions =

|absmag_v =

|notes = Has a symbiotic star system at its center

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

}}

The Southern Crab Nebula (or WRAY 16-147 or Hen 2-104) is a nebula in the constellation Centaurus. The nebula is several thousand light years from Earth, and its central star is a symbiotic Mira variable − white dwarf pair. It is named for its resemblance to the Crab Nebula, which is in the northern sky.

The Southern Crab was noted in a 1967 catalog, and was also observed using a CCD imager with the 2.2 meter telescope at the La Sila observatory in 1989. The 1989 observation marked a major expansion of knowledge about the nebula, and it was observed using various filters.{{Cite journal|last=Chiu|first=Liang-Tai George|date=August 1980|title=Space Telescope Astrometry from CCD images|journal=Celestial Mechanics|volume=22|issue=2|pages=191–196|doi=10.1007/bf01228806|s2cid=121065447 |issn=0008-8714}}

The nebula had already been observed using Earth-based telescopes, but images taken with the Hubble Space Telescope in 1999 have provided much more detail, revealing that at the center of the nebula are a pair of stars, a red giant and a white dwarf. It was imaged again by HST in 2019 with a newer instrument.

In 1999, it was imaged by the Hubble Space Telescope's Wide Field and Planetary Camera 2,{{Cite web|url=https://www.spacetelescope.org/images/opo9932a/|title=Southern Crab Nebula|last=|website=www.spacetelescope.org|access-date=2019-09-17}} noted for its unique "stair-step" crop and for such astrophotos as the Pillars of Creation.

The WFPC2 images were taken at an optical light wavelength of 658 nm.

The nebula was imaged again by the Hubble Space Telescope in 2019, and a set of images to celebrate the anniversary of the space telescope's launch in 1990 (29 years) by the Space Shuttle.{{Cite web|url=http://www.nasa.gov/image-feature/goddard/2019/hubble-celebrates-29th-anniversary-with-a-colorful-look-at-the-southern-crab-nebula|title=Hubble Celebrates 29th Anniversary with the Southern Crab Nebula|last=Hille|first=Karl|date=2019-04-18|website=NASA|access-date=2019-09-17}} This time a newer camera the WFC3 was used to image the nebula, at wavelengths filters of about 502, 656, 658, and 673 nanometers.{{Cite web|url=https://www.spacetelescope.org/images/heic1907a/|title=The Crab of the Southern Sky|last=|website=www.spacetelescope.org|access-date=2019-09-17}}

The designation {{Proper name|He2-104}} (or Hen 2-104) comes from the Henize catalog of 1967, Observations of Southern Planetary Nebulae.{{Cite web|url=http://www.messier.seds.org/xtra/supp/cats.html|title=List of Common Deep Sky Catalogs|website=www.messier.seds.org|access-date=2019-09-17}} The catalog includes 459 items identified as planetary nebula (or likely as such).{{Cite journal|last=Henize|first=Karl G.|date=April 1967|title=Observations of Southern Planetary Nebulae|url=https://ui.adsabs.harvard.edu/1967ApJS...14..125H/abstract|journal=The Astrophysical Journal Supplement Series|volume=14|pages=125|doi=10.1086/190151|bibcode=1967ApJS...14..125H }}{{Dead link|date=February 2023 |bot=InternetArchiveBot |fix-attempted=yes }} (note that in this meaning it does not imply exoplanets)

Another designation that it has been recorded for this object is WRAY-16-47.15677 - Spectroscopy and Imaging of the Southern Crab Nebul

In 2008, an investigation of the Southern Crab with its symbiotic (astronomical term) star was published.{{Cite web|url=https://www.researchgate.net/publication/1913657|title=Hen 2-104: A close-up look at the Southern Crab|website=ResearchGate|access-date=2019-09-18}} The study used imaging and spectroscopic data from space and Earth-surface telescopes including Hubble and VLT observatories. The ESO defines a symbiotic star system as "binaries in which a small hot star (white dwarf or main sequence star) orbits around a red giant star. These systems are often surrounded by an envelope of gas or dust; those with gas are known as S-types and those with dust as D-types."{{Cite web|url=https://www.eso.org/public/news/eso8901/|title=The "Southern Crab" Nebula|last=|website=www.eso.org|access-date=2019-09-18}}