Messier 62: Globular Cluster in Ophiuchus

M62 is a bright globular cluster in the far south of Ophiuchus, right on the border with Scorpius. It is one of the most lopsided globulars in the sky, and from mid-northern latitudes it stays low, so pick a night with a clear southern horizon.

What it is

M62 is a globular cluster about 19,700 light-years away. Its 15-arcminute size works out to about 86 light-years across. It is one of the globulars nearest the center of the Milky Way, and the galaxy's tidal pull has likely distorted it: its bright core sits off-center, giving it a lopsided look. The core is extremely dense and may have gone through core collapse. X-ray observations show many X-ray binaries, systems that form when stars pass close to each other, which is common in such a crowded center. M62 also has dozens of variable stars, mostly of RR Lyrae type. Its neighbor M19 looks similar but lies farther away.

When to see it

M62 is a summer object. It is highest around midnight in early June and well placed in the evening from June through August. From about 40°N it reaches only about 20° above the southern horizon, so haze and light pollution low in the south can wash it out. From the Southern Hemisphere it passes high overhead and is a far better sight.

How to find it

Start at Antares, the red heart of Scorpius. M62 lies about 8° east-southeast of it. A closer guide is Epsilon Scorpii, the bright star below Antares in the curve of the scorpion's body: M62 is about 5° north-northeast of Epsilon. In a finder it shows as a small fuzzy star. M19 lies about 4° due north of M62, so you can visit both in one sweep.

What you will see

In binoculars M62 is a small, bright, round glow. A small telescope shows a bright core with a fuzzy halo, and you may notice that the halo is brighter on one side. A 200 mm telescope at medium to high power begins to resolve the outer stars, and the off-center core becomes obvious. Its low altitude from northern sites is the main limit; steady air and a dark southern horizon help more than extra aperture.

History

Charles Messier first saw M62 on June 7, 1771, but did not measure its position accurately until June 4, 1779, so his catalog lists it under the later date. William Herschel was the first to resolve it into stars and noted its irregular shape.