Changing Planet

Photo: Scorpion’s Stinger Studded With Diamond Sash

This new image, from the ESO’s La Silla Observatory in Chile, shows the bright star cluster Messier 7. Easily spotted with the naked eye when looking in the direction of the tail of the constellation of Scorpius, this star cluster is one of the most prominent in the sky and an important research target. Credit: European Southern Observatory (ESO)


In the high desert of Chile, a giant telescope’s eye has opened ours to the true beauty of a well-known star cluster. Best of all, the starry bauble strikes the observer’s eyes from near the tip of a mythical Scorpion’s stinger.

One of the more popular deep-sky objects for backyard stargazers, Messier 7 is a brilliant group of about 100 stars located some 800 light-years from Earth. The star cluster sits at the back end of the constellation Scorpius, the Scorpion.

This new snapshot of Messier 7 comes courtesy of the 2.2-meter (7.2-foot) telescope at La Silla Observatory, located in the pristine, high-altitude Atacama desert of Chile. It offers an eye-catching, never-before-seen portrait of a sprinkling of bright blue-white stellar beacons spread across some 25 light-years of space.

Studding the stellar canvas beyond the cluster are hundreds of thousands of much fainter, more distant stars, which reside in the downtown core of our Milky Way galaxy.

Astronomers estimate that Messier 7’s member stars are no more than 200 million years old, making them middle-aged stars.

The brightest ones—about 10 percent of the cluster—live fast and furious lives. They are predicted to burn out quickly and end their lives violently, exploding as supernovae.

Eventually, in the far future, the remaining cluster members will slowly drift apart until they no longer are recognizable as a cluster.

Such star clusters are important to science because they shed light on how stars age: All of their members are born from the same primordial material at about the same time, which makes it much easier for astronomers to investigate their stellar properties.

See for Yourself

Sitting within the borders of the giant arachnid constellation, Messier 7 is easy to track down in the sky with binoculars. It can be glimpsed with the naked eye from dark skies. Shining at an overall magnitude 3, folks with keen eyes may even be able to spot it from light-polluted suburban skies.

In fact, the first record we have of Messier 7, also known as Ptolemy’s Cluster, comes from famed classical Roman astronomer Claudius Ptolemy, who spotted it in A.D. 130. He described it as a small cloudy patch at the end of the mythical beast’s curved tail.

Skychart showing location of Scorpius constellation low in the southeast sky just before dawn. Messier 7 star cluster sits just off the tip of the arachnid's tail. Credit: Starry Night software / A. /Fazekas
Sky chart showing location of Scorpius constellation low in the southeastern sky just before dawn as seen from southern latitudes. The Messier 7 star cluster sits just off the tip of the arachnid’s tail. Credit: Starry Night software/A. Fazekas

The main body of Scorpius is formed by a line of glittering stars—including the bright orange Antares—dipping down to the southern horizon. The tail curves back up in the sky to form a starry stinger. From bright suburban skies you may find it easier to recognize this association of stars as forming a giant, slanted letter J.

This chart shows the bright constellation of Scorpius. The location of the bright star cluster Messier 7  is indicated with a red circle. This cluster can be easily seen with the naked eye on a dark night as a fuzzy patch in the heart of the Milky Way. Credit: ESO, IAU and Sky & Telescope
This chart shows the bright constellation of Scorpius. The location of the bright star cluster Messier 7 is indicated with a red circle. This cluster can be easily seen with the naked eye on a dark night as a fuzzy patch in the heart of the Milky Way. Click on image to enlarge. Credit: ESO, IAU, and Sky & Telescope

While Scorpius is traditionally known as a summertime evening constellation, you can observe it in late winter as well.

However, at this time of year, Scorpius rides in the very low southern skies, appearing just before dawn for mid-northern latitude observers. That makes it a bit of a challenge to spot. Folks in southern parts of the United States and farther south have an easier time because the cosmic arachnid appears higher in the sky.

Messier 7 lies to the upper left of the tip of the Scorpion’s stinger—hanging about 10 degrees above the local horizon as seen from mid-northern latitudes and progressively higher in southerly latitudes. (Ten degrees is about equal to the height of your fist at arm’s length.)

And if you have binoculars or a telescope, don’t forget to scan this part of the sky. Even from light-polluted suburbs, you can see that the region is chock full of clusters and clouds of stars. That’s because Scorpius lies in the same direction as the Milky Way core—making it one of the best panoramic stargazing tour grounds around for sky-watchers.

Follow Andrew Fazekas, the Night Sky Guy, on Twitter,  Facebook, and his website.

Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.

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