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 - July 2017

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for July

Meteor Shower
Southern Delta Aquariids (Aquarids) meteor shower peaks on July 29

Northern Hemisphere
West:- Mercury (mag. -0.5 to +0.3) (second half of month)
Southwest:- Jupiter (mag. -2.0)
South:- Saturn (mag. +0.2)
West:- Jupiter
South:- Saturn
East:- Neptune (mag. +7.8)
Southwest:- Saturn
South:- Neptune
Southeast:- Uranus (mag. +5.8)
East:- Venus (mag. -4.1)

Southern Hemisphere
West:- Mercury (second half of month)
Northwest:- Jupiter
East:- Saturn
West:- Jupiter
North:- Saturn
East:- Neptune
West:- Saturn
North:- Neptune
Northeast:- Venus, Uranus

Deep Sky

Small telescopes:-
Messier 13 - M13 - Great Hercules Globular Cluster
Messier 92 - M92 - Globular Cluster
Messier 11 - M11 - The Wild Duck Cluster (Open Cluster)
Messier 7 - M7 - The Ptolemy Cluster (Open Cluster)
Messier 6 - M6 - The Butterfly Cluster (Open Cluster)
Messier 4 - M4 - Globular Cluster
Messier 8 - M8 - Lagoon Nebula (Emission Nebula)
Messier 16 - M16 - Eagle Nebula (Emission Nebula with Open Cluster)
Messier 20 - M20 - Trifid Nebula (Emission and Reflection Nebula)

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