Abell 84 (lowenthalm)

Celestial hemisphere: Northern · Constellation: Cassiopeia (Cas) · Contains: PK112-10.1 · TYC3650-115-1 · TYC3650-1226-1 · TYC3650-1229-1 · TYC3650-161-1 · TYC3650-263-1 · TYC3650-3-1 · TYC3650-37-1 · TYC3650-53-1 · TYC3650-56-1 · TYC3650-611-1 · TYC3650-627-1 · TYC3650-74-1 · TYC3650-853-1 · TYC3650-90-1 · TYC3650-97-1

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Abell 84

Acquisition type: Lucky imaging

Powered byPixInsight

Abell 84

Acquisition type: Lucky imaging

Spent some quality time on this object at a dark site at the end of July. Just got around to processing the data. I think I was afraid the data wouldn't be very good, but it turned out to be quite decent - the faintest objects are around 22nd magnitude in red or green (whichever is brighter). I think a dark sky helps with star colors, as well as faint deep sky objects.

Based on the parallax of the 18th magnitude central blue star that formed the nebula the distance to the nebula and its progenitor star should be about 7800 light years. Given this distance and the nebula being 1.9 x 2.1 arc min, the nebula should be about 5 light years across. This is pretty large, so it's an older nebula that is growing dim. The central star is nearing its dead white dwarf stage, but it still has an absolute magnitude (its magnitude if it was 10 parsecs from us) of around 6.6, so its still in the process of cooling and dimming down to an absolute magnitude of more like 10, which is typical of young white dwarfs.

To the lower right of the nebula just to the upper left of the bright orange star, you can see a 18th magnitude blue star with almost exactly the same color as Abell 84's central star. This object has been tagged in surveys (based on Gaia mission data) as a candidate white dwarf. It's blue and hot, but you can tell its not a bright blue main sequence star because its of its distance (based on Gaia parallax data) of only 1400 light years. This works out to a dim absolute magnitude of only around 10.5, consistent with it being a very young white dwarf. A main sequence star of similar color still fusing elements in its core would have an absolute magnitude of between -3 and -9 or at least 150,000 times brighter!

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Status	Advanced success
Started	...
Astrometry.net job	6281425
PixInsight job	4NXUCL7A8NRKM5L0XCBM1WQ6C9OORK4N
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	23h47m45s.865
RA (top/left)	23h48m52s.495
RA (top/right)	23h46m40s.789
RA (bottom/right)	23h46m39s.712
RA (bottom/left)	23h48m50s.593

Dec (center)	+51°24′12″.68
Dec (top/left)	+51°30′52″.10
Dec (top/right)	+51°31′12″.40
Dec (bottom/right)	+51°17′30″.82
Dec (bottom/left)	+51°17′10″.90

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Abell 84

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