RCW 88 is an
emission nebula
An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star. Among the several different types of emissio ...
in the southern
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The origins of the e ...
of
Circinus
Circinus is a small, faint constellation in the southern sky, first defined in 1756 by the French astronomer Nicolas-Louis de Lacaille. Its name is Latin for compass (drawing tool), compass, referring to the Technical drawing, drafting tool used ...
that first appeared in the 1960
astronomical catalog
An astronomical catalog or catalogue is a List (information), list or tabulation of astronomical objects, typically grouped together because they share a common type, Galaxy morphological classification, morphology, origin, means of detection, or ...
ue by Rodgers, Campbell & Whiteoak (
RCW) of
Hα
H-alpha (Hα) is a specific deep-red visible spectral line in the Balmer series with a wavelength of 656.28 nm in air and 656.46 nm in vacuum; it occurs when a hydrogen electron falls from its third to second lowest energy level. H-alpha ...
-emission
regions
In geography, regions, otherwise referred to as zones, lands or territories, are areas that are broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and the interaction of humanity and t ...
within the southern
Milky Way
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...
.
Earlier observers, like James Wray in 1966, misclassified this as a likely 12.0v magnitude
planetary nebula
A planetary nebula (PN, plural PNe) 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 ...
,
[
] but later spectroscopic investigations revealed this as a diffuse nebulae.
RCW 88 was then to be identified by the infrared satellite
IRAS
The Infrared Astronomical Satellite (Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a survey of the entire night sky at infrared wavelengths. Launched on 25 January 1983, its mission lasted ten mo ...
as an
HII region
An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds ...
.
Deep red images reveal that the inner nebula is divided into two parts by a central dark lane, and there is evidence of a larger halo of fainter nebulosity extending perhaps out to 10 arcmin. The RCW catalogue states the Hα image size is 3'×2.
RCW 88 is located about 3300 parsecs (10,000 light years)
from us, though other estimates place this at a closer 1800±300 pc.
or 1800±200 pc.
Assuming the former distance and the diameter as 5'-6' across, finds by simple trigonometry the true size subtends a minimum of 5±1
parsec
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...
s (16±3 light-years.) This small emission nebula shows a mean radial velocity of −18 km.s
−1,
and is also a faint radio source that was identified by Lloyd Higgs in 1971.
Due to the large distance from us, astronomers have made few studies into the nature of RCW 88.
Field Star
There is a 10.8v magnitude star identified as TYC 8702-56-1 positioned at
RA : 15h 07m 25.1s
Dec. : –57° 48' 32" (2000),
place 137 arc seconds southwest of the centre of the bright nebulosity.
It is unlikely that this star is associated with the nebulosity being probably a field star.
References
Emission nebulae
Circinus (constellation)
Star-forming regions
{{Circinus