NGC 7635 revisited





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NGC 7635 is an emission nebula located in the constellation Cassiopeia. This nebula emits, mainly, in H alpha and Oxygen III. The central bubble is one out of the three shells of emitting gas that surround the hot, O6.5 class, star SAO 20575 (also known as BD+60°2522). Amazingly, this star, which originated the bubble and fuels its emission with its enormous radiation output, is not located at the center of the bubble, due to its movement. It is the star located half way between the center and its lower left border. This star is about 4 million years old (just one thousandth of our Sun’s age) and is expected to explode as supernova in about 15 million years (give or take a couple million…). By coincidence, this nebula lies superimposed to a region where another supernova exploded many thousands of years ago. Its gas wisps were faint enough to remain undiscovered until 2005. These remains are out of this image (just a few arc minutes left of the left border).


This image has been taken with narrowband filters (Halpha, [OIII] and [SII]) and has been color mapped to a modified Hubble Palette as well as to the natural colors. This is yet another result of the ongoing collaboration with Christian Sasse.


Additional Information


Name(s): NGC 7635

Type: Emission Nebula

RA:  23h 20m 42s

Dec: +61º 11’ 55”

Constellation: Cassiopeia

Size (arcmin): 15×8 arcmin

Magnitude: +11.0

Distance: 1400 ly


Date: 2023-10-30 to 2023-11-14

Location: Curiosity2 Observatory, New Mexico Skies, Mayhill, NM, USA

Size (arcmin): 17.0 x 14.3 arcmin

Telescope: 24” (61 cm) f/6.5 Reflector

Camera: FLI PL16803 (4096x4096pix)

Guiding: Astrodon MonsterMOAG off-axis guider

Total exposure: 28h 20m (Ha: 9h 20m; OIII: 10h; SII: 6h; RGB: 3h)

Processing: CCDStack, PixInsight (one step) and Photoshop CC 2023

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