Home > Ephemeris Program, Observing, Star Cluster > 06/13/2023 – Ephemeris – Messier 13, the Great star cluster in Hercules

06/13/2023 – Ephemeris – Messier 13, the Great star cluster in Hercules

June 13, 2023

This is Bob Moler with Ephemeris for Tuesday, June 13th. Today the Sun will be up for 15 hours and 32 minutes, setting at 9:29, and it will rise tomorrow at 5:56. The Moon, 3 days past last quarter, will rise at 3:34 tomorrow morning.

About a third of the way between the bright stars Vega which is high in the east and Arcturus, high in the south, can be found the Keystone of Hercules, a four-star box wider at the top than at the bottom. Along the right edge, a third of the way down is what looks like a faint star to someone with really good vision. In binoculars the star becomes fuzzy. One needs a larger telescope probably six or eight inches in diameter to begin to see some stars among the fuzziness. That is a globular star cluster containing hundreds of thousands of stars. This is the Great Hercules Globular Star Cluster. It’s beautiful if seen in a large telescope, such as the one brought out to the star parties at the Sleeping Bear Dunes, especially in August and September.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT –4 hours). They may be different for your location.

Addendum

Hercules globular star cluster finder
Hercules with all the stars visible in binoculars and its two globular star clusters: M13 and M92. M13 is almost bright enough to be spotted with the naked eye. It is easily visible in binoculars as a tiny fuzzy spot. It takes a telescope with an aperture of 6-8″ or 150 – 200 mm to begin to see some individual stars. M92 is dimmer and harder to resolve. Created using Cartes du Ciel (Sky Charts).
M 13
M 13, the Great Globular Star Cluster in Hercules. Note that the two stars at lower left and upper right make a squat isosceles triangle with M 13. That’s a way of recognizing it in binoculars. Credit: Scott Anttila, former member and president of the Grand Traverse Astronomical Society.
M 13 or Messier 13, the Great Hercules Globular Star Cluster, contains hundreds of thousands of stars, and is located around 25 thousand light years away. Credit: Daniel Dall’Olmo, Grand Traverse Astronomical Society member.

Dan’s image is rotated from Scott’s. The bright star at the lower left of Scott’s image is the same as the one at the lower left of Dan’s.

Globular star clusters are uniformly very old. M 13 is estimated to be between 11 and 12 billion years old, more than twice as old as our Sun and the solar system. As I say in my talks: “They don’t make them like that any more.” Globular clusters form a spherical distribution around the Milky Way galaxy with an increasing concentration toward the center. Do they reveal the original spherical shape of the galaxy before the gas and dust collapsed into the disk of the galaxy we see today? The star clusters that form today lie in the disk, and contain a few hundreds or a thousand stars. They are called open or galactic star clusters. The Pleiades is the most famous example of this type of star cluster.

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