RCW 58


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The RCW (Rodgers, Campbell and Whiteoak) catalogue compiles, in the authors’ words, “the HII regions distributed about the galactic equator within galactic latitude limits ±15°”. It contains HII emission regions of the Southern Hemisphere that were listed in connection with a joint work they did at Mount Stromlo, Australia, under Bart Bok’s supervision. This catalogue contains 181 objects, all of them with remarkable beauty and scientific interest.

RCW 58, has both of them, beauty and interest. This nebula is the result (just like NGC 6164-5) of the intense mass ejection by a massive star. In this case, the star is HD 96548, a Wolf-Rayet star, WR40. These stars are usually very massive, from 20 up to 60+ solar masses, and are very hot (30,000 to 200,000 K). Their nature has two major consequences: they eject off material at a fast pace and they live short (5 to 20 million years). Very often, they end up (or are expected to) in an explosion as supernova. RCW 58 clearly shows the ejected mass and the effect of the fierce radiation pressure on the ejected gases. Although the shape (ring) and mechanism of formation (mass ejection) of this nebula have many things in common with planetary nebulae, RCW 58 is not a planetary. Planetary nebulae have a smaller, degenerate, low-mass star, usually a white dwarf, in their center.

This 23 hour-deep image, taken in narrowband for higher contrast, shows the elaborate structure in the HII region carved by WR40’s radiation, the OIII-rich extensions around the nebula as well as a reddish HII background region on the Eastern (right) side of the nebula. This background region is seldom seen in images of this nebula.

Additional Information


Name(s): RCW 58

Type: Emission Nebula

RA:  11h 06m 08s

Dec: -65º 29’ 11”

Constellation: Carina

Size (arcmin): 8×5

Magnitude: 10.5

Distance: 13,000 ly


Date: 2018-03-24 thru 2018-04-08

Location: iTelescope.net, SSO near Coonabarabran, NSW Australia

Size (arcmin): 33×33

Telescope: Planewave CDK 20” f/6.8

Camera: SBIG STX16803 (4096x4096pix)

Guiding: Astrodon MonsterMOAG off-axis guider

Total exposure: 23 hours (Ha: 14 h; OIII: 7.5 h; RGB 1.5 h)

Processing: CCDStack, Photoshop CC 2018

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