M2

M2

Messier 2 or M2 (also designated NGC 7089) is a globular cluster in the constellation Aquarius. It has an apparent visual magnitude of 6.5 and its angular diameter is 12.9 arc-minutes. M2 lies at an estimated distance of 37,900 light years. The Equinox 2000 coordinates are RA= 21h 33.5m, Dec= +00° 49´ which makes M2 best seen during the autumn. The Messier Autumn Star Chart shows the position of all Messier objects visible during that season.

The image above shows the uncropped view of M2 through the Takahashi E-180 Astrograph (North is to right). A 3x enlargement of this image appears to the right.

In spite of its inclusion in the Messier Catalog, this globular cluster was actually discovered by G. D. Maraldi in 1746. Charles Messier independently discovered it in 1760, as a "nebula without stars." It was William Herschel who first resolved M2 into individual stars. M2 is unusally elliptical in shape compared to most spherically symetric globular clusters. It contains approximately 150,000 stars.

According to Recio-Blanco et al.(2005), the distance of M2 is 40,850 light years and its diameter is 190 light years. Its estimated mass is 900,000 solar masses and it contains 30 variable stars.

For more information, see the Messier Catalog as well as specific entries for M2 in Wikipedia and SEDS.

Messier's Description of M2

September 11, 1760
`Nebula without star in the head of Aquarius, its center is brilliant, and the light surrounding it is round; it resembles the beautiful nebula which is situated between the head and the bow of Sagittarius [M22], it is seen very well with a telescope of 2 feet, placed below the parallel [same Dec] of Alpha of Aquarius. M. Messier has reported this nebula on the chart of the track of the comet observed in 1759. Mem. Acad. of the year 1760, page 464. M. Maraldi has seen this nebula in 1746 while observing the comet which appeared that year. (Diam. 4')'

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