The Large Globular Cluster in Hercules

Illustration showing the six tails of a comet in the morning sky

There are comets, and then there are big comets. It was certainly the fire that broke out in the sky in 1743 and 1744. One of the most recent.

As the comet sped past Earth toward the Sun, the comet is said to have been bright enough to be seen in daylight and outwit Venus in the evening sky. It also developed a long and clearly visible double tail, which is already unusual. Then, as it reached perihelion and orbited the Sun, the comet’s tail split into six clearly defined rays. In the morning, with the comet’s head still hidden below the horizon, these six tails were bright and visible, reaching the sky as a sort of “fan” that appeared to come from the sun.

Why the comet had this appearance remains a mystery. There might actually be a much wider tail or two, but there were areas that were obscured by the thick dust. In any case, it was recorded by astronomers around the world, including in China, where court astronomers claimed the comet made a crackling noise. That was a very strange sin.

Not tall young Catherine noticed the culprit when she went to Russia for marriage. Apparently, she thought about announcing her future greatness because… of course she did.

Back in France, the young Messier also seems to have seen the comet and seems to have come a long way to leading it to a future in astronomy, rather than the downright wonderful career path of leading people into the courtroom. Messier managed to get a job as an assistant to Joseph Nicolas Deliel, who was the official astronomer of the French Navy (drawing course, etc.) and perhaps most importantly, the filthy rich.

Deile had a newly built observatory and young Messier settled in quickly. Over the next decade he made a number of important discoveries and received senior government positions and a number of honors and memberships in the scientific community. As expected, comets have remained a topic of particular interest to Messier, and he seemed good at getting rid of a distant comet before other astronomers could find their names on the approaching snowball. Even King Louis XV. gave Messier a very impressive nickname, namely ” Mongoose Comets” which, if you are going to have a title engraved on your headstone, the title should be.

But Messier’s later work with deep sky objects is best remembered today. Beginning in 1771, Messier began compiling a catalog of some of these misty patches in the night sky—things we know today as nebulae, galaxies, and star clusters. The first list contained 45 such articles. The final list, which included some items from Messier’s footnotes and marginal notes, totaled 110. These became known as wretches.

Since then, finding these Messier objects has been a right-of-way for astronomers. Something like climbing the Seven Summits in mountaineering. Except for a much lower chance of dying in an avalanche.

And…well, it turns out that Messier 13 is something known variously as the Hercules Star Cluster, Greater Globular Cluster of Hercules, or Hercules Globular Cluster. Messier wasn’t actually the first to discover M13. This credit goes to another comet man, Edmund Halley, who met him in 1714. But Messier included it in the catalogue,

M13 is a group of hundreds of thousands of stars, but not a galaxy. In fact, it’s one of many such blobs orbiting our good old galaxy, the Milky Way. It is about 22,500 light-years from Earth. If you want to find him, look where the name suggests – in the constellation Hercules. But bring a telescope. Despite the number of stars in this group, their apparent magnitude is over 11 and they are too faint to be seen with the naked eye.

M13 is about 100 times more densely packed with stars than neighboring regions around Earth. There are only about 135 stars within 50 light years of Earth. It’s interesting to imagine what a sky the size of a neighbor might look like on a clear night. The stars in M13 are closer together than ever, and then a pair merge into a short-lived blue-white giant.

Something about M13 has made the spherical Hercules cluster a recurring theme in science fiction novels. This may be why SETI collaborators on the missing but not forgotten Arecibo telescope looked for a target for a test message in 1974 and settled on M13. Somewhere in between here and there a letter with basic information about mathematics, which then expands to describe the structure of atoms, then elements, then DNA and then some basic facts about human life.

If someone is out there and has a very good recipient, they will have mail in about 22,450 years.

As with most of the images I show in this feature, the top image was taken with the small but clever Vespera telescope. And as usual with this feature, I expect some of you will do much better. But maybe not better than that…

Bild des Hubble-Teleskop M13.

Web-Countdown: “NASA, in partnership with the European Space Agency and the Canadian Space Agency, will release the first full-color images and spectroscopy data for the James Webb Space Telescope during a televised broadcast beginning Tuesday, July 12 at 10:30 a.m. ET. And we’re broadcasting it live.