NGC 6888 Crescent Nebula (Alex Woronow)

NGC 6888 Crescent Nebula

NGC 6888 Crescent Nebula

OTA: RH-305 (12” f/3.5)

Camera: SBIG STX-16803

Observatory: Deep Sky West

EXPOSURES:

Red: 11 x 600

Blue: 6 x 600

Green: 9 x 600

Hydrogen: 22 x 1200

Oxygen: 11 x 1200

Total exposure ~21 hours

Image Width: ~40 arcminutes

Processed by Alex Woronow (2020) using PixInsight, Topaz, Skylum, Starnet++, SWT

NGC 6888, The Crescent Nebula,looks much like a planetary nebula, which, when a star, at the end of its life, explodes and sheds the gasses surrounding its core. But this is not a simple planetary nebula. Instead, a Wolf-Rayet (WR 136) star spawned this nebula. WR stars are hotter than virtually all other stars, WR 136 is about 70,000 K. In just 4.7M yrs (about the age of our solar system) this star has exhausted its hydrogen fuel supply and is now burning helium. At the end of its hydrogen-burning stage, this 21 solar-mass star became a red supergiant star--that was just a couple of 100M years ago. It is expected to “go supernova” withing a few hundred thousand years more.

NGC 6888 consists of material blown from WR 136’s surface between 120,000 and 240,000 years ago. The ejected mass is about 5 solar masses and is still expanding at 80 km/s. The stellar wind from WR 136 currently moves outward at 1,700 km/s and is shredding and shaping NGC 6888--my starless image shows the wind-swept shapes being formed. The nebula ‘glows’ in H-alpha and OIII emissions as the ions are energized by the UV radiation from the Wolf-Rayet star.

The wind-gas collisions spawns a shock wave, actually two shock waves, one moving into NGC 6888 and further exciting and sculpting it, and one moving back toward WR 136, heating the out-flow gas to such a high temperature that it is emitting X-rays.

That’s not tranquil spot in the Galaxy!

(Source: largely Wikipedia)

Final
Original
B

B

Description: Starless

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Status	Advanced success
Started	...
Astrometry.net job	3583063
PixInsight job	BUBCTY2170BMVO5S2MORRRHVDKUQ1EU3
PixInsight queue size	n/a
PixInsight stage	n/a

RA (center)	20h12m11s.47
RA (top/left)	20h13m54s.54
RA (top/right)	20h10m29s.90
RA (bottom/right)	20h10m29s.44
RA (bottom/left)	20h13m52s.65

Dec (center)	+38°18′32″.0
Dec (top/left)	+38°38′00″.1
Dec (top/right)	+38°38′12″.3
Dec (bottom/right)	+37°58′58″.2
Dec (bottom/left)	+37°58′47″.4

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