M75 (mag. +8.7) is a very distant and compact globular cluster located in eastern Sagittarius. At 67,500 light years from Earth it's one of the more remote Messier globulars and hence appears faint and small from our perspective. It's located far beyond the galactic centre (46,700 light-years) and almost on the opposite side of the galaxy to us. Despite this, M75 is intrinsically bright and on nights of good seeing and transparency can be glimpsed with a pair of 7x50 or 10x50 binoculars.

M75 was discovered by Pierre Méchain on the night of August 27, 1780. Charles Messier observed it soon after and added it to his catalogue a few weeks later. It was William Herschel who first resolved M75 into stars describing it (like M62 and M70) as a "miniature version of M3."

M75 is located right at the Sagittarius-Capricornus border. It's positioned about 23 degrees northeast of the centre of the Sagittarius "Teapot" asterism and 5.5 degrees north and a little east of a small group of four faint naked-eye stars (59 Sgr - mag. +4.5, 60 Sgr - mag. +4.8, 62 Sgr - mag. +4.4 and ω Sgr - mag. +4.7). The globular is best seen during the months of June, July and August from the Southern Hemisphere and the tropics.

M75 globular cluster (NOAO/AURA/NSF)

Finder Chart for M75 (also shown M22, M25, M28, M54, M55, M69 and M70)

Finder Chart for M75 (also shown M22, M25, M28, M54, M55, M69 and M70) - pdf format

Finder Chart for M72 (also shown M30, M73 and M75)

Finder Chart for M72 (also shown M30, M73 and M75) - pdf format

For binocular observers M75 appears stellar in nature. A 100mm (4-inch) telescope at high magnifications will start to pick out a certain degree of fuzziness. The cluster however appears small, visually spanning only 3 arc minutes in diameter. It's roughly comparable in size and brightness to the Messier globulars located within the teapot (M54, M69 and M70). To begin resolution, larger telescopes of the order of 250mm (10-inch) or more are required.

In total M75 covers 6.8 arc minutes of apparent sky, which corresponds to a spatial diameter of 134 light-years. It's very old at 13 Billion years plus and is estimated to contain 400,000 stars. Classified as class I, M75 is one of the more densely concentrated globular clusters known. However, despite been faint and small it's a remarkable globular given its incredible, extragalactic-like distance.

M75 Data Table

Object TypeGlobular cluster
Distance (kly)67.5
Apparent Mag.8.7
RA (J2000)20h 06m 05s
DEC (J2000)-21d 55m 17s
Apparent Size (arc mins)6.8 x 6.8
Radius (light-years)67
Age (years)>13,000M
Number of Stars400,000
Notable FeatureDistant globular and one of the most densely concentrated clusters known

Sky Highlights - March 2017

Comet 41P/Tuttle-Giacobini-Kresak now visible with binoculars as it heads towards perihelion

Mercury heading towards greatest elongation east

Minor Planet
Vesta now visible with binoculars and small telescopes.

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for March 2017

Northern Hemisphere
West:- Venus (mag. -4.8 to -4.1 - first half of month), Mars (mag. +1.3 to +1.5), Uranus (mag. +5.9), Mercury (mag. -1.5 to -0.4 - second half of month)
Southeast:- Jupiter (mag. -2.3 to -2.5)
Southwest:- Jupiter
Southeast:- Saturn (mag. +0.5)

Southern Hemisphere
West:- Venus (first half of month), Mars, Uranus
North:- Jupiter
East:- Saturn
West:- Jupiter
Northeast:- Saturn
East:- Neptune (mag. +8.0 - second half of month)

Deep Sky
Naked eye / binoculars:-
Melotte 111 - Mel 111 - The Coma Star Cluster (Open Cluster)
Messier 44 - M44 - The Praesepe (Open Cluster)

Messier 67 - M67 - Open Cluster
Messier 51 - M51 - The Whirlpool Galaxy (Spiral Galaxy)
Messier 97 - M97 - The Owl Nebula (Planetary Nebula)
Messier 101 - M101 - The Pinwheel Galaxy (Spiral Galaxy)
Messier 65 – M65 – Spiral Galaxy
Messier 66 - M66 - Intermediate Spiral Galaxy
Messier 95 - M95 - Barred Spiral Galaxy
Messier 96 - M96 - Intermediate Spiral Galaxy
NGC 4244 - Spiral Galaxy
NGC 4565 - Needle Galaxy - Spiral Galaxy

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