The Southern Crab Nebula (or WRAY 16-147 or Hen 2-104) is a

nebula A nebula (; or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral, or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regions, such as in the Pillars of Creation in ...

in the constellation

Centaurus Centaurus () is a bright constellation in the southern sky. One of the 88 modern constellations by area, largest constellations, Centaurus was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one ...

. The nebula is several thousand

light year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by t ...

s from Earth, and its central star is a

symbiotic Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biolo ...

Mira variable Mira variables (named for the prototype star Mira) are a class of pulsating stars characterized by very red colours, pulsation periods longer than 100 days, and amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wave ...

−

white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...

pair. It is named for its resemblance to the

Crab Nebula The Crab Nebula (catalogue designations M1, NGC 1952, Taurus A) is a supernova remnant and pulsar wind nebula in the constellation of Taurus (constellation), Taurus. The common name comes from a drawing that somewhat resembled a crab with arm ...

, which is in the northern sky. The Southern Crab was noted in a 1967 catalog, and was also observed using a

CCD imager A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...

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. The nebula had already been observed using Earth-based telescopes, but images taken with the

Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...

in 1999 have provided much more detail, revealing that at the center of the nebula are a pair of stars, a

red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The stellar atmosphere, outer atmosphere is inflated and tenuous, making the radius large and the surface t ...

and a

. 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 The Wide Field and Planetary Camera 2 (WFPC2) is a camera formerly installed on the Hubble Space Telescope. The camera was built by the Jet Propulsion Laboratory and is roughly the size of a baby grand piano. It was installed by servicing mission ...

, noted for its unique "stair-step" crop and for such astrophotos as the

Pillars of Creation ''Pillars of Creation'' is a photograph taken by the Hubble Space Telescope that depicts elephant trunks of interstellar gas and dust in the Eagle Nebula of the Serpens constellation, some from Earth. These elephant trunks had been disco ...

. 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 The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...

. This time a newer camera the WFC3 was used to image the nebula, at wavelengths filters of about 502, 656, 658, and 673 nanometers. The designation (or Hen 2-104) comes from the Henize catalog of 1967, ''Observations of Southern Planetary Nebulae''. The catalog includes 459 items identified as

planetary nebula A planetary nebula is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. The term "planetary nebula" is a misnomer because they are unrelated to planets. The ...

(or likely as such). (note that in this meaning it does not imply exoplanets) Another designation that it has been recorded for this object is WRAY-16-47. In 2008, an investigation of the Southern Crab with its symbiotic (astronomical term) star was published. 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."

Gallery

Southern Crab Nebula_center.jpg, Close up of the center of the Nebula Southern Crab Nebula_overview.jpg, The Southern Crab Nebula in its entirety STSCI-H-p1915b-f-SouthernCrabNebula-20190418.png, Southern Crab Nebula – (18 April 2019;annotated) STSCI-H-p1915d-f-SouthernCrabNebula-Shape-20190418.png, Southern Crab Nebula – (18 April 2019;Shape)

References

External links

The "Southern Crab" Nebula (He2-104) in 1989
(captures the crab like presentation) {{DEFAULTSORT:Southern Crab Nebula Centaurus Planetary nebulae Emission nebulae

Gallery

See also

References

External links