M70 is an eighth magnitude globular cluster located in Sagittarius that's faintly visible with binoculars, appearing "star" like. It's much easier to spot with small telescopes where despite being small with little detail visible, it appear obviously non-stellar. To resolve M70 into stars large amateur scopes are required.

Charles Messier discovered M70 on August 31, 1780, describing it as a "nebula without star". On the same night he also discovered M69, another close by globular (both apparently and spatially). M70 has an extremely dense core and is believed at some time previously to have suffered a core collapse, similar to Messier globulars M15, M30 and possibly M62. It was William Herschel who first resolved M70 into stars, describing it as a miniature version of M3.

M70 is located 29,300 light years from Earth. Spatially, it's separated by only 1,800 light-years from M69 with both objects located close to the galactic centre. They are best seen from the Southern Hemisphere during the months of June, July and August. However, from northern temperate latitudes they are never well positioned, at best climbing just a few degrees above the southern horizon.

Messier 70 globular cluster by the Hubble Space Telescope (NASA, The Hubble Heritage Team (AURA/STScI))

Finder Chart for M70 (also shown M6->M8, M18, M20->M24, M28, M54, M55 and M69)

Finder Chart for M70 (also shown M6->M8, M18, M20->M24, M28, M54, M55 and M69) - pdf format

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

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

Finding M70 is easy once familiar within the teapot asterism of Sagittarius. Locate the two stars that make up the base of the teapot, Kaus Australis (ε Sgr - mag. +1.8) and Ascella (ζ Sgr - mag. +2.6). Imagine a line connecting these two stars. M70 is positioned almost exactly halfway along this line.

At magnitude +8.0, M70 is much easier to spot with larger 11x70 or 20x80 binoculars than with standard size models. When viewed through 80mm (3.1-inch) scopes, the globular appears as a faint diffuse ball of light with a slightly brighter central region. Telescope apertures of 250mm (10-inch) or larger are required to start resolving some of the outer stars. In total, M70 covers 8 arc minutes of apparent sky but through amateur scopes, visually it appears much smaller than this. The cluster is estimated to be 12.8 billion years old and contains 75,000 stars.

M70 made headlines in 1995 when Alan Hale and Thomas Bopp observed it and discovered the great comet Hale-Bopp nearby.

M70 Data Table

Messier70
NGC6681
Object TypeGlobular cluster
ConstellationSagittarius
Distance (kly)29.3
Apparent Mag.8.0
RA (J2000)18h 43m 13s
DEC (J2000)-32d 17m 31s
Apparent Size (arc mins)8 x 8
Radius (light-years)34
Age (years)12,800M
Number of Stars75,000
Notable FeatureBelieved to have previously suffered a core collapse

Sky Highlights - March 2017

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

Mercury
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
Evening
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)
Midnight
Southeast:- Jupiter (mag. -2.3 to -2.5)
Morning
Southwest:- Jupiter
Southeast:- Saturn (mag. +0.5)

Southern Hemisphere
Evening
West:- Venus (first half of month), Mars, Uranus
Midnight
North:- Jupiter
East:- Saturn
Morning
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)

Telescopes:-
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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