Starship Asterisk*

The Medusa Nebula

Explanation: Braided and serpentine filaments of glowing gas suggest this nebula's popular name, The Medusa Nebula. Also known as Abell 21, this Medusa is an old planetary nebula some 1,500 light-years away in the constellation Gemini. Like its mythological namesake, the nebula is associated with a dramatic transformation. The planetary nebula phase represents a final stage in the evolution of low mass stars like the sun as they transform themselves from red giants to hot white dwarf stars and in the process shrug off their outer layers. Ultraviolet radiation from the hot star powers the nebular glow. The Medusa's transforming star is the faint one near the center of the overall bright crescent shape. In this deep telescopic view, fainter filaments clearly extend above and left of the bright crescent region. The Medusa Nebula is estimated to be over 4 light-years across.

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APOD Robot wrote: ↑Fri Mar 25, 2022 4:05 am
Explanation: Braided and serpentine filaments of glowing gas suggest this nebula's popular name, The Medusa Nebula. Also known as Abell 21, ...

Abell 21 (AGC 21) is a galaxy cluster. For the Medusa Nebula it's better to use the exact name PN A66 21.
https://hla.stsci.edu/cgi-bin/display?c ... bined) A21

Nice pic too from the VLT:

ESO’s Very Large Telescope in Chile has captured the most detailed image ever taken of the Medusa Nebula. Image credit: ESO. https://www.eso.org/public/images/eso1520a

AVAO wrote: ↑Fri Mar 25, 2022 6:13 am Abell 21 (AGC 21) is a galaxy cluster. For the Medusa Nebula it's better to use the exact name PN A66 21.

It's a bit confusing, because there are two "Abell catalogs". One of galaxy clusters, one of planetary nebulas. The Medusa Nebula is Abell 21 in the second.

Formally, the first is referenced as "AGC" and the second as "A66", but casually both are just referred to as "Abell". (Not that I disagree with your point that the latter name is preferable, particularly if someone wants to look up the object in a database like Simbad for further information.)

Maybe the future of the sun? Nasty old woman!

Can you recognize her face in NVSS radio?

The six faces of medusa: Multi-wavelength 6-image montage of Abell 21. Note the GALEX UV data reveals
the central ionising star whereas the WISE data reveals the inner ionised zone where the MIR
[OIV] line (red in this 22µm IRAS band) is a proxy for HeII in the optical.

Docment source:https://www.researchgate.net/publicatio ... la_surveys

Chris Peterson wrote: ↑Fri Mar 25, 2022 11:50 am

AVAO wrote: ↑Fri Mar 25, 2022 6:13 am Abell 21 (AGC 21) is a galaxy cluster. For the Medusa Nebula it's better to use the exact name PN A66 21.

It's a bit confusing, because there are two "Abell catalogs". One of galaxy clusters, one of planetary nebulas. The Medusa Nebula is Abell 21 in the second.

Formally, the first is referenced as "AGC" and the second as "A66", but casually both are just referred to as "Abell". (Not that I disagree with your point that the latter name is preferable, particularly if someone wants to look up the object in a database like Simbad for further information.)

I was getting no good hits with a search for "abell 21 galaxy cluster". And a search for "abell 21" or "abell21" universally pointed to the nebula, not the cluster. But eventually I stumbled on this hit for ABELL21:

https://heasarc.gsfc.nasa.gov/db-perl/W ... uinox=2000

johnnydeep wrote: ↑Fri Mar 25, 2022 8:38 pm

Chris Peterson wrote: ↑Fri Mar 25, 2022 11:50 am

AVAO wrote: ↑Fri Mar 25, 2022 6:13 am Abell 21 (AGC 21) is a galaxy cluster. For the Medusa Nebula it's better to use the exact name PN A66 21.

It's a bit confusing, because there are two "Abell catalogs". One of galaxy clusters, one of planetary nebulas. The Medusa Nebula is Abell 21 in the second.

Formally, the first is referenced as "AGC" and the second as "A66", but casually both are just referred to as "Abell". (Not that I disagree with your point that the latter name is preferable, particularly if someone wants to look up the object in a database like Simbad for further information.)

I was getting no good hits with a search for "abell 21 galaxy cluster". And a search for "abell 21" or "abell21" universally pointed to the nebula, not the cluster. But eventually I stumbled on this hit for ABELL21:

https://heasarc.gsfc.nasa.gov/db-perl/W ... uinox=2000

Okey. I stumbled across this in aladin, when i entered "abell 21" under target...
http://aladin.unistra.fr/AladinLite/?ta ... 2%2Fcolor

Very nice except for the small guiding error, very unfortunately..

johnnydeep wrote: ↑Fri Mar 25, 2022 8:38 pm

Chris Peterson wrote: ↑Fri Mar 25, 2022 11:50 am

AVAO wrote: ↑Fri Mar 25, 2022 6:13 am Abell 21 (AGC 21) is a galaxy cluster. For the Medusa Nebula it's better to use the exact name PN A66 21.

It's a bit confusing, because there are two "Abell catalogs". One of galaxy clusters, one of planetary nebulas. The Medusa Nebula is Abell 21 in the second.

Formally, the first is referenced as "AGC" and the second as "A66", but casually both are just referred to as "Abell". (Not that I disagree with your point that the latter name is preferable, particularly if someone wants to look up the object in a database like Simbad for further information.)

I was getting no good hits with a search for "abell 21 galaxy cluster". And a search for "abell 21" or "abell21" universally pointed to the nebula, not the cluster. But eventually I stumbled on this hit for ABELL21:

https://heasarc.gsfc.nasa.gov/db-perl/W ... uinox=2000

Well, like I said, there are two separate catalogs with "Abell" in their names, AGC which is a catalog of galaxy clusters, and A66 which is a catalog of emission nebulas. And at various times, objects in both have been called simply "Abell XX".

orin stepanek wrote: ↑Fri Mar 25, 2022 1:28 pm

Click to view full size image

Maybe the future of the sun?

Click to view full size image

Nasty old woman!

Thanks for posting a picture of Medusa, Orin!

I wish Art was here. He would have had something quirky to say about Medusa.

Art, where Art thou?

Ann

Ann wrote: ↑Sat Mar 26, 2022 5:15 am

orin stepanek wrote: ↑Fri Mar 25, 2022 1:28 pm ...

Click to view full size image

Nasty old woman!

Thanks for posting a picture of Medusa, Orin!

I wish Art was here. He would have had something quirky to say about Medusa.

Art, where Art thou?

Ann

Yeah, neufer is missed. Would Medusa be an unfortunate name for an online U.S. pharmacy company? The domain name medusa.com seems to be available for sale in case anyone is interested.