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Andromeda and Ghost. Today's spectacular and surprising APOD
What are these gigantic blue arcs near the Andromeda Galaxy (M31)? Discovered in 2022 by amateur astronomers, the faint arcs -- dubbed SDSO 1 -- span nearly the same angular size as M31 itself.
At first, their origin was a mystery: are they actually near the Andromeda Galaxy, or alternatively near to our Sun? Now, over 550 hours of combined exposure and a collaboration between amateur and professional astronomers has revealed strong evidence for their true nature: SDSO 1 is not intergalactic, but a new class of planetary nebula within our galaxy.
Dubbed a Ghost Planetary Nebula (GPN), SDSO 1 is the first recognized member of a new subclass of faded planetary nebulas, along with seven others also recently identified...
https://apod.nasa.gov/apod/ap250804.html
At first, their origin was a mystery: are they actually near the Andromeda Galaxy, or alternatively near to our Sun? Now, over 550 hours of combined exposure and a collaboration between amateur and professional astronomers has revealed strong evidence for their true nature: SDSO 1 is not intergalactic, but a new class of planetary nebula within our galaxy.
Dubbed a Ghost Planetary Nebula (GPN), SDSO 1 is the first recognized member of a new subclass of faded planetary nebulas, along with seven others also recently identified...
https://apod.nasa.gov/apod/ap250804.html
To recap: this Astronomy Picture Of the Day shows an entirely new-to-science astronomical entity not recognized until 2022 when was found by back-yard astronomers!
The telescope was probably invented in 1608 by Deutsch-Dutch spectacle-maker Hans Lipperhey. The first documented telescopic astronomical observations were likely made in 1609 by Englishman Thomas Harriot well over 400 years ago. He beat Galileo by at least a month.
Whilst this Ghost Nebula, unlike Andromeda, is not something you can just look up in the sky and see—indeed, it is probable that it can only be "seen" by many hours of digital camera exposure and post-processing—it is, none-the-less, something which has been there all of this time.
The lesson? Keep Looking Up with an Open Mind!
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BTW, the white blob on the upper right is a dwarf elliptical satellite galaxy of Andromeda.
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