Name and/or Catalogue Designations:
Designations: M53 (NGC 5024) Designations: NGC 5053
Visual
Magnitude: 7.7 Visual
Magnitude: 9
Size: 13 min diameter
Size: 10 min diameter
Distance: 56000 light
years Distance: 53500 light
years
Discoverer: Johan Elert Bode, 1775
Discoverer: William Herschel
on March 14, 1784
Visual Description: Globular star cluster M53 is one of the more outlying globulars, being about 60,000 light years away from the Galactic center, and almost the same distance (about 58,000 light years) from out Solar system. At this distance, its apparent angular diameter of 13' corresponds to a linear diameter of roughly 220 light years. It is rapidly approaching us at a velocity between 79 km/s and 112 km/s. M53 has a bright compact central nucleus of about 2' in diameter, although its stars are not very concentrated toward the center when compared to other globulars, and a gradually decreasing density profile to the outer edges.
Its discoverer Johann Elert Bode, who found it on February 3, 1775, described it as a "rather vivid and round" nebula. Charles Messier, who independently rediscovered and cataloged it two years later, on February 26, 1777, found it "round and conspicuous" and that it resembles M79. William Herschel was the first to resolve it into stars, and found it similar to M10.
As in all globular clusters, the stars of M53 are apparently "metal-poor", which means that they contain only little quantities of elements heavier than helium (actually mainly elements like carbon and oxygen); those of M53 are even below the average globular cluster members in "metallicity". It contains the considerably respectable number of 47 known RR Lyrae variables, some of them were reported to have changed their periods irreversibly with time (Kenneth Glyn-Jones).
In small amateur telescopes, M53 appears as a slightly oval nebulous object with a large, bright center, of rather even surface brightness and evenly fading out to the edges. Mallas reports that he saw many stars in the 4-inch refractor under excellent viewing conditions, with the central part appearing somewhat grainy. In somewhat larger telescopes, its outer fringes appear resolved into stars, while the central part is still unresolved and grainy, with one star standing out, in telescopes of about 8-inch aperture. Large instruments of about 12-inch up show it well resolved, with a moderately concenterated nucleus and stars spread out to about 12 arc minutes diameter.
At only about 1 degree separation to the east, the faint and quite loose globular cluster NGC 5053 comes into the field of view. NGC 5053 was discovered by William Herschel on March 14, 1784 and cataloged as H VI.7. NGC 5053 is at roughly the same distance as M53 (53,500 light years), indicating that these clusters are also physically rather close together. NGC 5053 is of a much lesser stellar density than its prominent neighbor, and particularly lacks a concentrated bright nucleus.
At a distance of about 53,500 light-years from us, NGC 5053's apparent diameter of 10.5 arc minutes corresponds to a linear extension of about 160 light-years. The cluster shines at a visual brightness of about 9.5 magnitudes, and a photographic magnitude 10.5. Its absolute visual magnitude is only about -6.72, corresponding to an intrinsic luminosity of about 40,000 times that of our sun. It is receding from us at about 44 km/s.
Because of its moderate stellar content, the nature of this cluster as a
globular has been doubted in the past, but spectroscopic investigations have
now firmly re-established this classification: The stars of NGC 5053 are old
and poor in heavy elements. Its horizontal-branch stars are of about mag 16.65,
and its brightest stars are at mag 13.8.
Seeing Conditions:
above average
Telescope: Stellarvue SV80S
80mm f6.0 APO refractor
Focal
Length: 480mm with 0.8x reducer = 384mm
Mount: Takahashi NJP 160
Camera: SBIG ST10XME
Exposure:
several 5-minute
exposures
Other:
Image Processing: CCDStack and Photoshop CS2
The Visual description of M53 and NGC5053 where borrowed from the Students for the Exploration and Development of Space (SEDS) http://www.seds.org/
Copyright(c) 2007 Doug Sanqunetti. All rights reserved
