Astronomy Picture of the Day
    


APOD: 2025 August 4 B Blue Arcs Toward Andromeda
<< Yesterday 4.08.2025
APOD: 2025 August 4 B Blue Arcs Toward Andromeda
Credit & Copyright: Ogle et al.
Explanation: 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. Shown in blue are extremely faint oxygen emission from the shock waves, while the surrounding red is a hydrogen-emitting trail that indicates the GPN's age.

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
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Based on Astronomy Picture Of the Day