NGC 7635 also known as the Bubble Nebula is a HII region emission nebula located in northwestern Cassiopeia close to the border with Cepheus. It appears round in shape due to expanding gas from the stellar wind of a massive hot central star (mag. +8.7). The nebula is located in a giant molecular cloud that glows due to excitation from the star. It was discovered by William Herschel on November 3, 1787.

NGC 7635 (credit:- NASA, ESA, and The Hubble Heritage Team (STScI/AURA))

NGC 7635 is located 0.5 degrees southwest of open cluster M52 with open cluster NGC 7510 positioned a further 1.5 degrees to the southwest. Although shinning at magnitude +6.9, the Bubble Nebula is a difficult object for small scopes due to its diffuse shape and low surface brightness. A 150mm (6-inch) scope is the minimum aperture recommended for this target.

The nebula is best seen from northern latitudes during the months of August, September and October when it appears high in the sky and even overhead from some locations. It's circumpolar from latitudes greater than 28N.

Finder Chart for NGC 7635 (credit:- freestarcharts)

Finder Chart for NGC 7635 - pdf format (credit:- freestarcharts)

With a 200mm (8-inch) scope, NGC 7635 appears as a large faint shell of light that's brightest around the central star. To the north and southeast fainter wisps can be detected, which can be enhanced using an UHC filter. In addition averted vision also helps. In total, NGC 7635 spans some 15 x 8 arc minutes of apparent sky but large scopes are required to reveal significant elongation. It lies approximately 9,000 light-years distant and is number 11 in the Caldwell catalogue.

NGC 7635 Data Table

NameBubble Nebula
Object TypeEmission Nebula
Distance (light-years)9,000
Apparent Mag.6.9
RA (J2000)23h 20m 45s
DEC (J2000)61d 12m 45s
Apparent Size (arc mins)15 x 8
Radius (light-years)20 x 10
Other NameSharpless 162 (Sh2-162)

Sky Highlights - March 2017

Comet 41P/Tuttle-Giacobini-Kresak now visible with binoculars as it heads towards perihelion

Mercury heading towards greatest elongation east

Minor Planet
Vesta now visible with binoculars and small telescopes.

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for March 2017

Northern Hemisphere
West:- Venus (mag. -4.8 to -4.1 - first half of month), Mars (mag. +1.3 to +1.5), Uranus (mag. +5.9), Mercury (mag. -1.5 to -0.4 - second half of month)
Southeast:- Jupiter (mag. -2.3 to -2.5)
Southwest:- Jupiter
Southeast:- Saturn (mag. +0.5)

Southern Hemisphere
West:- Venus (first half of month), Mars, Uranus
North:- Jupiter
East:- Saturn
West:- Jupiter
Northeast:- Saturn
East:- Neptune (mag. +8.0 - second half of month)

Deep Sky
Naked eye / binoculars:-
Melotte 111 - Mel 111 - The Coma Star Cluster (Open Cluster)
Messier 44 - M44 - The Praesepe (Open Cluster)

Messier 67 - M67 - Open Cluster
Messier 51 - M51 - The Whirlpool Galaxy (Spiral Galaxy)
Messier 97 - M97 - The Owl Nebula (Planetary Nebula)
Messier 101 - M101 - The Pinwheel Galaxy (Spiral Galaxy)
Messier 65 – M65 – Spiral Galaxy
Messier 66 - M66 - Intermediate Spiral Galaxy
Messier 95 - M95 - Barred Spiral Galaxy
Messier 96 - M96 - Intermediate Spiral Galaxy
NGC 4244 - Spiral Galaxy
NGC 4565 - Needle Galaxy - Spiral Galaxy

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