M70 is an eighth magnitude globular cluster in Sagittarius that's faintly visible with binoculars, appearing as a star like point of light. It's much easier to spot with small telescopes where it appears obviously non-stellar but without detail. To resolve M70 into stars, larger scopes are required.

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

M70 is located 29,300 light-years away. Physically it's separated by just 1,800 light-years from M69 with both objects located near to the galactic centre. The clusters are best seen from the Southern Hemisphere during the months of June, July and August. From mid-northern latitudes they are never well positioned and at best climb just a few degrees above the horizon.

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

Finder Chart for M70 (credit:- freestarcharts)

Finder Chart for M70 - pdf format (credit:- freestarcharts)

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

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

Finding M70 is easy once familiar within the teapot asterism of Sagittarius. First 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 7x50 or 10x50 models. When viewed through 80mm (3.1-inch) scopes, it appears as a faint diffuse ball of light with a slightly brighter central region. Telescopes of the order of 250mm (10-inch) or larger are required to begin resolving some of the outer stars.

In total, M70 covers 8 arc minutes of apparent sky, but visually it appears much smaller than this. The cluster is estimated to be 12.8 billion years old and contains around 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 (light-years)29,300
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)12.8 Billion
Number of Stars75,000
Notable FeatureBelieved to have previously suffered a core collapse

Sky Highlights - July 2017

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for July

Meteor Shower
Southern Delta Aquariids (Aquarids) meteor shower peaks on July 29

Northern Hemisphere
Evening
West:- Mercury (mag. -0.5 to +0.3) (second half of month)
Southwest:- Jupiter (mag. -2.0)
South:- Saturn (mag. +0.2)
Midnight
West:- Jupiter
South:- Saturn
East:- Neptune (mag. +7.8)
Morning
Southwest:- Saturn
South:- Neptune
Southeast:- Uranus (mag. +5.8)
East:- Venus (mag. -4.1)

Southern Hemisphere
Evening
West:- Mercury (second half of month)
Northwest:- Jupiter
East:- Saturn
Midnight
West:- Jupiter
North:- Saturn
East:- Neptune
Morning
West:- Saturn
North:- Neptune
Northeast:- Venus, Uranus

Deep Sky

Small telescopes:-
Messier 13 - M13 - Great Hercules Globular Cluster
Messier 92 - M92 - Globular Cluster
Messier 11 - M11 - The Wild Duck Cluster (Open Cluster)
Messier 7 - M7 - The Ptolemy Cluster (Open Cluster)
Messier 6 - M6 - The Butterfly Cluster (Open Cluster)
Messier 4 - M4 - Globular Cluster
Messier 8 - M8 - Lagoon Nebula (Emission Nebula)
Messier 16 - M16 - Eagle Nebula (Emission Nebula with Open Cluster)
Messier 20 - M20 - Trifid Nebula (Emission and Reflection Nebula)

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