M102 is a galaxy catalogued by Charles Messier that hasn't yet been explicitly identified. It was Pierre Méchain who made the original observation in March 1781, before passing the information onto Messier who catalogued it without verification. However, Méchain believed M102 was an error and even wrote a letter on May 6, 1783 expressing his view that the object was in fact a duplicate of M101. Historical, evidence based on Messier's description of the galaxy, combined with its co-ordinates, suggest that M102 could well be lenticular galaxy NGC 5866, also known as the Spindle galaxy. A number of other possible candidates have emerged, but it seems likely that Messier and Méchain both at some time observed NGC 5866, and therefore we include it as the missing item.

The Spindle galaxy (mag. +9.9) is located at the southern edge of the far northern constellation of Draco. It's positioned four degrees southwest of Iota Draconis (ι Dra - mag. +3.3). Directly west of NGC 5866 are the seven stars that form the famous "Plough" or "Big Dipper" asterism of Ursa Major.

NGC 5866 is a challenging binocular object, but much easier to spot with small scopes. It's best seen from Northern Hemisphere locations during the months of April, May and June. From latitudes of 35N or greater, this galaxy is circumpolar and therefore never sets.

M102 the Spindle Galaxy by the Hubble Space Telescope (credit:- NASA, The Hubble Heritage Team (AURA/STScI))

Finder Chart for M102 (credit:- freestarcharts)

Finder Chart for M102 - pdf format (credit:- freestarcharts)

Under dark skies, small 80mm (3.1-inch) refractors show NGC 5866 as a thin saucer shape smudge of nebulosity spanning 4.7 x 1.9 arc minutes. Through 150mm (6-inch) or 200mm (8-inch) reflectors, it appears as a halo of greenish tinged light with a well-defined bright central core. The view also hints at the dark dust lane that spans the length of the galaxy. Photographically, NGC 5866 is a beautiful sight with the dusk disk spectacular.

The Spindle galaxy is located 50 million light-years away and has a radius of 70,000 light-years. It's estimated to contain about 100 billion stars.

M102 Data Table

Messier102
NGC5866
Object TypeLenticular Galaxy
ClassificationS0
ConstellationDraco
Distance (light-years)50 Million
Apparent Mag.+9.9
RA (J2000)15h 06m 29s
DEC (J2000)+55d 45m 47s
Apparent Size (arc mins)4.7 x 1.9
Radius (light-years)35,000
Number of Stars100 Billion
Notable FeatureDisputed Messier object

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

Southern Hemisphere
Evening
West:- Mercury (second half of month)
Northwest:- Jupiter
East:- Saturn
Midnight
West:- Jupiter
North:- Saturn
East:- Neptune
Morning
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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