Messier 55
Observation data (J2000 epoch)
Class	XI
Constellation	Sagittarius
Right ascension	19h 39m 59. The Messier objects are a set of Astronomical objects first listed by French astronomer Charles Messier in his "Catalogue des Nébuleuses In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. The Shapley–Sawyer Concentration Class is a classification system on a scale of one to twelve using Roman numerals for Globular clusters according to their concentration In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture Right ascension (abbrev RA; symbol α) is the Astronomical term for one of the two Coordinates of a point on the Celestial sphere 40s[1]
Declination	-30° 57′ 43. In Astronomy, declination (abbrev dec or δ) is one of the two coordinates of the Equatorial coordinate system, the other being either 5″[1]
Distance	17. 3 kly (5. A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by 3 kpc)
Apparent magnitude (V)	+7. History The first direct measurements of an object at interstellar distances were undertaken by German Astronomer Friedrich Wilhelm Bessel in 1838 The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value 42[1]
Apparent dimensions (V)	19′. 0
Physical characteristics
Mass	kg ( M)
Radius	48 ly[2]
Other designations	M55, NGC 6809, GCl 113[1]
See also: Globular cluster, List of globular clusters
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Messier 55 (also known as M55 or NGC 6809) is a globular cluster in the constellation Sagittarius. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. The New General Catalogue ( NGC) is the best-known catalogue of Deep sky objects in Amateur astronomy. A globular cluster is a spherical collection of Stars that orbits a galactic core as a Satellite. This is a list of Globular clusters. The apparentmagnitude does not include an extinction correction A globular cluster is a spherical collection of Stars that orbits a galactic core as a Satellite. In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture It was discovered by Nicolas Louis de Lacaille in 1751 and catalogued by Charles Messier in 1778. Abbé Nicolas Louis de Lacaille ( March 15, 1713 &ndash March 21, 1762) was a French Astronomer. Year 1751 ( MDCCLI) was a Common year starting on Friday (link will display the full calendar of the Gregorian calendar (or a Charles Messier ( June 26, 1730 &ndash April 12, 1817) was a French astronomer most notable for publishing an Year 1778 ( MDCCLXXVIII) was a Common year starting on Thursday (link will display the full calendar of the Gregorian calendar (or M55 is at a distance of about 17,300 light-years away from Earth. A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Only about half a dozen variable stars have been discovered in M55. For the astronomical object see Variable star. Variable Star is a 2006 novel written by Spider Robinson

External links

• Messier 55, SEDS Messier pages

References

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