The Wild Duck Cluster is one of the most well-known star clusters in the Messier catalog. Scientifically known as Messier 11, or M11, this bright bundle of stars is an open cluster — one of the richest in the entire galaxy and the most distant one in the Messier collection that can still be seen with the naked eye.
According to NASA, this open star cluster gets its colloquial name from the arrangement of its brightest stars, which roughly resembles the letter “V.” Located 6,000 light-years from Earth in the constellation Scutum (“The Shield”), the Wild Duck Cluster is home to nearly 3,000 stars — which flock together in the shape of a triangular patch of light as seen through a telescope.
Unlike globular star clusters — ancient formations that pack hundreds of thousands of stars and date back from the early days of the Milky Way, as the Inquisitr recently reported — open star clusters are much younger and only loosely bound by gravity.
The bright stars in the Wild Duck Cluster sparked into existence a mere 250 million years ago, notes NASA. These stars all formed together from the same molecular cloud — a large and dense accumulation of gas and dust, usually referred to as a “stellar nursery.”
The general consensus is that stars in open clusters are typically born in a single generation — given that their radiation would normally blow away nearby material needed to churn out more stars. However, the Wild Duck Cluster has presented astronomers with an enigma concerning the birth of its stars.
The big mystery of M11 has always been whether its stars were all born in a single wave or in multiple generations. This is because its stars shine in different colors despite having the same brightness — which suggests they are of different ages.
A close-up of the Wild Duck Cluster — imaged below by the Hubble Space Telescope — reveals that some of its stars glow in bright shades of blue, while others sparkle in a reddish hue that suggests they could be older.
Recent observations of the Wild Duck Cluster have finally solved the riddle, revealing the true age of the stars in this intriguing open cluster, reports Science Daily.
The mystery was unraveled by a team of astronomers from Belgium and Korea, which studied the cluster with the MMT telescope at the University of Arizona and discovered that the stars in M11 were all born in the same generation 250 million years ago.
Writing in the journal Nature Astronomy, the scientists explain that the stars in this open cluster appear to have diverse colors not because of their age difference but due to their rotation.
“Astronomers plot young stars’ brightness and color in a diagonal line — from bright, blue and massive at the top of the line, down to faint, red and less massive at the bottom — called the main sequence,” shows a news release from the University of Arizona.
In a typical open cluster, the stars turn brighter and redder as they grow old, veering off the diagonal at the same point — which suggests that they are all of the same age. In the Wild Duck Cluster, however, the stars have different rotation speeds, which causes them to veer off from the main sequence at different points.
“Rotational speed is like a fountain of youth to a star: The faster it spins, the better it mixes hydrogen — the star’s fuel — into its core. The more hydrogen the core receives, the longer the star lives, causing it to appear redder than younger siblings.”
“A rapidly rotating star can remain in the main sequence stage longer than a slowly rotating star,” said study lead author Beomdu Lim, an astronomer affiliated both with the Université de Liège in Belgium and with Kyung Hee University in Korea. “A wide range of velocities of stars results in differences of lifetimes among the stars.”