RCW 34, RCW 35 & RCW 36
HII Regions in the Vela Molecular Ridge. Vela
This image is dominated by RCW 35 (Gum 18), but also contains RCW 36 (Gum 20) and RCW 34 (Gum19) in the constellation of Vela.
RCW 35 appears to be located at a similar distance as Vela OB1 and is in the same direction as the complex of reflection nebula called Bran 196a-c.
RCW 36 is an emission nebula containing an open cluster. This H II 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. The VMR is made up of several distinct clouds, and RCW 36 is embedded in the VMR Cloud C.
RCW 36 is one of the sites of massive-star formation closest to the Solar System, whose distance of approximately 700 parsecs (2300 light-years). The most massive stars in the star cluster are two stars with late-O or early-B spectral types, but the cluster also contains hundreds of lower-mass stars. This region is also home to objects with Herbig–Haro jets, HH 1042 and HH 1043.
Like most star-forming regions, the interstellar medium around RCW 36 contains both the gas from which stars form and some newly formed young stars. Here, young stellar clusters form in giant molecular clouds. 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 form when the mass gas in part of a cloud becomes too great, causing it to collapse due to the Jeans instability. 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.
The Vela Molecular Ridge can be subdivided into several smaller clouds, each of which in turn can be subdivided into cloud “clumps”. The molecular cloud clump from which the RCW 36 stars are forming is Clump 6 in the VMR C cloud.
Early maps of the region were produced by radio telescopes that traced emission from several types of molecules found in the clouds, including CO, OH, and H2CO. More detailed CO maps were produced in the 1990s by a team of Japanese astronomers using the NANTEN millimeter-wavelength telescope. Using emission from C18O, they estimated the total mass of Cloud C to be 44,000 M☉. The cloud maps suggest that Cloud C is the youngest component of the VMR because of an ultra-compact H II region associated with RCW 36 and several sites of embedded protostars, while H II regions in other VMR clouds are more evolved. Observations from the Herschel Space Telescope show that the material within the cloud is organized into filaments and RCW 36 sits near the south end of a 10-parsec long filament.
Star formation in RCW 36 is currently ongoing. In the dense gas at the western edge of RCW 36, where the far-infrared emission is greatest, are found protostellar cores, the Herbig Haro objects, and an ultra-compact H II region. However, more deeply embedded star-formation is obscured by dust, so radiation can only escape from the cloud surface and not from the embedded objects themselves.
RCW 34 is a H II region and emission nebula located approximately 22,000 light years from Earth. Named after Australian astronomer Colin Stanley Gum. The nebula is relatively dark. However, when observed using infrared wavelengths, two different areas are visible – one half of the nebula is bright,and the other is dark. The bright side is the hydrogen illuminated by a nearby blue supergiant star, and dark is the place where new stars surround the central star on the other side. The source of energy that stimulates the nebula RCW 34 to shine is a huge, extremely hot star V391 Velorum with a surface temperature of up to 30,000 °C. Because it is a variable star, it evokes violent phenomena, including discards of matter shells, affecting the composition and light emission of the RCW 34 nebula. Stars of the type V391 Velorum do not burn long enough to explode as supernovae. It can be expected that the explosion of the central star will completely change the RCW 34 nebula.
RCW 35 appears to be located at a similar distance as Vela OB1 and is in the same direction as the complex of reflection nebula called Bran 196a-c.
RCW 36 is an emission nebula containing an open cluster. This H II 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. The VMR is made up of several distinct clouds, and RCW 36 is embedded in the VMR Cloud C.
RCW 36 is one of the sites of massive-star formation closest to the Solar System, whose distance of approximately 700 parsecs (2300 light-years). The most massive stars in the star cluster are two stars with late-O or early-B spectral types, but the cluster also contains hundreds of lower-mass stars. This region is also home to objects with Herbig–Haro jets, HH 1042 and HH 1043.
Like most star-forming regions, the interstellar medium around RCW 36 contains both the gas from which stars form and some newly formed young stars. Here, young stellar clusters form in giant molecular clouds. 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 form when the mass gas in part of a cloud becomes too great, causing it to collapse due to the Jeans instability. 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.
The Vela Molecular Ridge can be subdivided into several smaller clouds, each of which in turn can be subdivided into cloud “clumps”. The molecular cloud clump from which the RCW 36 stars are forming is Clump 6 in the VMR C cloud.
Early maps of the region were produced by radio telescopes that traced emission from several types of molecules found in the clouds, including CO, OH, and H2CO. More detailed CO maps were produced in the 1990s by a team of Japanese astronomers using the NANTEN millimeter-wavelength telescope. Using emission from C18O, they estimated the total mass of Cloud C to be 44,000 M☉. The cloud maps suggest that Cloud C is the youngest component of the VMR because of an ultra-compact H II region associated with RCW 36 and several sites of embedded protostars, while H II regions in other VMR clouds are more evolved. Observations from the Herschel Space Telescope show that the material within the cloud is organized into filaments and RCW 36 sits near the south end of a 10-parsec long filament.
Star formation in RCW 36 is currently ongoing. In the dense gas at the western edge of RCW 36, where the far-infrared emission is greatest, are found protostellar cores, the Herbig Haro objects, and an ultra-compact H II region. However, more deeply embedded star-formation is obscured by dust, so radiation can only escape from the cloud surface and not from the embedded objects themselves.
RCW 34 is a H II region and emission nebula located approximately 22,000 light years from Earth. Named after Australian astronomer Colin Stanley Gum. The nebula is relatively dark. However, when observed using infrared wavelengths, two different areas are visible – one half of the nebula is bright,and the other is dark. The bright side is the hydrogen illuminated by a nearby blue supergiant star, and dark is the place where new stars surround the central star on the other side. The source of energy that stimulates the nebula RCW 34 to shine is a huge, extremely hot star V391 Velorum with a surface temperature of up to 30,000 °C. Because it is a variable star, it evokes violent phenomena, including discards of matter shells, affecting the composition and light emission of the RCW 34 nebula. Stars of the type V391 Velorum do not burn long enough to explode as supernovae. It can be expected that the explosion of the central star will completely change the RCW 34 nebula.
Telescope: Astro Physics 155EDF (TCC) f5.4
Mount: Astro Physics 1600GTO
Camera: FLI PL29050 / CFW2-7
Guider: Agena Starguide II / ZWO ASI178MM
Filters: Astrodon II 50mm LRGB
L: 63×10 mins = 630 mins, R: 21×10 mins = 210 mins, G: 24×10 mins = 240 mins, B: 24×10 mins = 240 mins
Total Imaging Time: 22h 00m
Data Imaged remotely on 5 nights during February 2024.
Imaged from Observatorio El Sauce, Chile, in partnership with Fred Espenak.
Data acquisition & Processing by David Churchill.
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