RCW 36 AKA GUM 20

 STAR FORMATION REGION IN VELA (THE SHIP SAIL)

(Image centered at: ra 08h:59 m / dec - 43º 44')

CLICK THE IMAGE FOR A HIGH RESOLUTION VIEW

https://www.baskies.com.ar/PHOTOS/RCW%2036%20LRGB%20QSI583%20WS%20HR.htm

December 2025, Observatorio Cielos Albertnos, Buenos Aires, Argentina

DATA

TYPE: Emision Nebula

APPARENT DIAMETER:  6 arc minutes (a bit more in deep images renditions)

APPARENT MAGNITUDE (V): na

DISTANCE: 2300 light years

IMAGE INFORMATION

INSTRUMENT: Orion Optics UK 6" Newtonian with Ultra Grade Optics working at f 4.5

CAMERA: QSI 583WS Mono Camera

MOUNT: SKY WATCHER NEQ6 Guided off axis with SX Lodestar Mono Camera 

FILTERS: Baader LRGB Set 

SKY CONDITIONS: Bortle 3 skies

OBJECT DESCRIPTION AND IMAGE SESSION

RCW 36 (also designated as Gum 20) is an emission nebula containing an open cluster in the constellation Vela. This HII region is part of a larger-scale star-forming complex known as the Vela Molecular Ridge (VMR), a collection of molecular clouds in the Milky Way that contain multiple sites of ongoing star-formation activity. RCW 36 is one of the closest massive star formation region to our Solar System, at a distance of  approximately 2300 light years or 700 parsecs. The nebula spans over a diameter of 1.6 light years.

Like most star-forming regions, the interstellar medium around RCW 36 contains both the gas from which stars are born and some newly formed young stars. Molecular clouds are the coldest, densest form of interstellar gas and are composed mostly of molecular hydrogen (H2), but also include more complex molecules, cosmic dust, and atomic helium. Stars develop when the mass gas becomes too great, causing it to collapse due to the Jeans instability. The Jeans instability is a concept in astrophysics that describes an instability that leads to the gravitational collapse of a cloud of gas or dust which leads to star formation.

Most stars do not form alone, but in groups containing hundreds or thousands of other stars. RCW 36 is an example of this type of "clustered" star formation.

Some objects are also captured in this image: the small bluish patch at the lower middle left is vdBH28 and to the upper left we have BBW207.