M102

M102

Messier 102 or M102 is a bit of a puzzle since its true identity is ambiguous. Discovered by Pierre Méchain, he later claimed that it was a duplicate observation of Messier 101. However, there are historical and observational reasons to believe that it is actally NGC 5866. For the purposes of this web page, I will accept the latter identification.

Messier 102 or M102 (also designated NGC 5866) is a lenticular galaxy in the constellation Draco. It has an apparent visual magnitude of 9.9 and its angular diameter is 5.2x2.3 arc-minutes. M102 lies at an estimated distance of 40 million light years. The Equinox 2000 coordinates are RA= 15h 06.5m, Dec= +55° 46´ which makes M102 best seen during the summer. The Messier Summer Star Chart shows the position of all Messier objects visible during that season.

The image above shows the uncropped view of M102 through the Takahashi E-180 Astrograph (North is up). A 3x enlargement of this image appears to the right.

This galaxy was discovered by Méchain in 1781. It is one of four lenticular galaxies in the Messier Catalog (M84, M85, M86, and M102). Some authorities believe the M102 is actually a duplicate observation of M101 while others accept the identification as NGC 5866. According to Stoyan et al. (2010), the distance of M102 (aka NGC 5866) is 40.8 million light years and its diameter is 71,000 light years.

For more information, see the Messier Catalog as well as specific entries for M102 in Wikipedia and SEDS.

Messier's Description of M102

(Méchain)
`Nebula between the stars Omicron of Bootes and Iota of the Dragon [Draco]: it is very faint; near it is a star of the sixth magnitude.'

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