Medusa nebula (Abell 21)

The Medusa nebula, also known as Abell 21, is a planetary nebula in the constellation Gemini. 

It was discovered by astronomer George O. Abell in 1955 on the photographic plates of the Palomar Observatory Sky Survey (POSS), and he listed it as number 21 in his catalogue of Planetary Nebulae.

For a long time it was considered a supernova remnant because of its filamentary structure, but the measurement of its high expansion velocity and the fact that no post-supernova neutron star was found finally confirmed that it was a planetary nebula. 

The spectrum of the nebula clearly shows a weaker than usual O III role (the literature says that Ha is 1.7 times stronger).

The Medusa nebula is about 4 light years across and lies about 1500 light-years away from us.

At the bottom left of the image is also NGC 2395, a small open star cluster with 30 stars.

The image is presented in the H-OIII-OIII palette (with RGB stars) and accumulates 28 hours of exposure time. 

Unfortunately, in this image I could not collect all the exposure I wanted in OIII, which (combined with the lower presence in the nebula of this component mentioned above), affects the final result.

Image taken remotely from my observatory in Àger.

Click on the image for a higher resolution version, or go to the Gallery section for complete exposure details.

Observatory automation and remote operation with 

No comments:

Post a Comment