There is significant uncertainty about what object this entry in the RCW catalog actually refers to.
The RCW catalog describes this as a faint 4x4 arcminute nebula and the exact coordinates of the object appear to be the same as the radio HII region [KC97c] G320.4-01.1
More recent sensitive studies such as the SHASSA hydrogen-alpha survey
show that this nebula is next to and possibly part of a far larger region of emission centred on the extended star cluster / OB association Pismis 20
SIMBAD identifies RCW 89 with the young supernova remnant SNR 320.4-01.0, and certainly emission from this supernova remnant dominates the nebula as the filaments in the image here show. A 2005 study gives a distance 5200 +/- 1400 parsecs and an age for the central pulsar of 1700 years.
Humphreys gives a distance of 3980 parsecs for Pismis 20 and lists 6 ionising stars, including the O 9.5 I supergiant Pismis 20 #11
. SIMBAD lists several other hot stars in the same direction, including the O 8.5 I supergiant Pismis 20 #2
, the O9 III giant Pismis 20 #9
and the Wolf-Rayet star WR 67
A 1988 paper suggests that SNR 320.4-01.0 may
be part of Pismis 20 and the currently available distance estimates seem to make this a possibility. Another possibility is that we are looking at two objects in this direction, with a large faint diffuse nebula surrounding Pismis 20 in the Centaurus arm and the brighter more distant SNR 320.4-01.0 located in the 3Kpc arm or perhaps the galactic bar region.
The Georgelins conclude that RCW 87, 88 and 89 are part of the same structure located at a distance of 3000-4000 pc, most likely closer to 3000 pc.
You can see a spectacular recent Chandra x-ray image of the pulsar wind nebula within the supernova remnant, often called the "Hand nebula", here
. You can see the full extent of the nebula surrounding Pismis 20 in this false colour hydrogen-alpha image
Supernova remnant may be part of Pismis 20. [1
See this article for a recent review of this large and visible SNR. Gives a distance of 5200 +/- 1400 parsecs and a pulsar characteristic age of 1700 years.[2
RCW 87, 88 and 89 are part of the same structure located at a distance of 3000-4000 pc, most likely closer to 3000 pc.[3
1700 years old[4
1. ^ Peterson, C. J. (1988). "UBV Photometry in Four Southern Open Clusters
Associated (?) with Supernova Remnants", Bulletin of the American
Astronomical Society, Vol. 20, 716. [1988BAAS...20..716P]
2. ^ Yatsu, Y., Kawai, N., Kataoka, J., et al. (2005). "Chandra Observation of
the Interaction between the Hot Plasma Nebula RCW 89 and the Pulsar Jet of
PSR B1509-58", The Astrophysical Journal, Vol. 631, 312-319.
3. ^ Georgelin, Y. M., Boulesteix, J., Georgelin, Y. P., et al. (1987).
"Galactic structure around longitude L = 317 deg determined from CIGALE
observations", Astronomy and Astrophysics, Vol. 174, 257-269.
4. ^ Gaensler, B. M., Brazier, K. T. S., Manchester, R. N., et al. (1999). "SNR
G320.4-01.2 and PSR B1509-58: new radio observations of a complex
interacting system", Monthly Notices of the Royal Astronomical Society,
Vol. 305, 724-736. [1999MNRAS.305..724G]