101 must-see cosmic objects: the group of wild ducks
The summer sky is for the birds – literally. There’s Cygnus the Swan, Aquila the Eagle, the Eagle Nebula, and even a flock of wild ducks in the tiny constellation Scutum the Shield.
The cluster of wild ducks (M11) was discovered in 1681 by German astronomer Gottfried Kirch, who described it as “a small dark speck with a star shining through it”. It wasn’t until 1733, however, that English clergyman, philosopher, and scientist William Derham resolved the dark spot of Kirch into countless stars. M11 is about 6,100 light-years away and covers a region about 23 light-years in diameter. This places it in the Sagittarius arm of the Milky Way, along with deep sky treasures such as the Eagle Nebula and the Omega Nebula. Discovering M11 on your own is best done by first locating the diamond-shaped body of Aquila the Eagle, then its tail-feathered stars, Lambda (λ) and 12 Aquilae. These combine with Eta (η) Scuti to form a three-star arc that curves right towards M11.
The Wild Duck Cluster gets its nickname from the V-shaped pattern formed by its brightest stars. Describing the appearance in his classic 1844 book A Cycle of Celestial Objects, Admiral William Smyth wrote that the group “somewhat resembles a flight of wild ducks”. While this analogy may be true with smaller telescopes, it is lost with ranges much larger than 6 inches in aperture.
M11 is one of the richest and most compact open clusters found in the sky. According to some accounts, it contains over 2,900 stars. While most stars in M11 shine at magnitude 10 and below, the single star noted by Kirch shines at magnitude 8. This star is a blue main-sequence star, like many others in the heap. There are also several red and yellow giants scattered throughout, adding pops of color to the scene. Based on the study of these giants, astronomers have estimated the age of M11 at around 220 million years.
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