Telescope Captures Fascinating New Images Of Star Cluster Messier 7
Have you ever wondered about the brilliant scorpion shaped cluster of stars in the night sky? Well, this cluster of stars has fascinated astronomers for years and was first explained by mathematician and astronomer Claudius Ptolemy, as early as 130 AD, who described it as a "nebula following the sting of Scorpius".
This bright cluster of about 100 stars, called the Messier 7 or NGC 6475, is located around 800 light years from Earth. According to a press release Wednesday, in a new picture taken from the Wide Field Imager on the MPG/ESO 2.2-meter telescope, the Messier 7 stands out against a very rich background of hundreds of thousands of fainter stars. It points in the direction of the center of the Milky Way.
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There are two types of star clusters: global clusters and open clusters. Open clusters like Messier 7 contain loosely clustered groups of stars born at almost the same time and place, from large cosmic clouds of gas and dust in their host galaxy. These open star clusters are of great interest to scientists since the stars in them have about the same age and chemical composition and are thus useful in studying about cluster structures and evolution.
Messier 7 is about 200 million years old spanning a region of space about 25 light-years across. Over time, many of the brightest stars in the cluster get disrupted due to external gravitational forces and will violently explode as supernovae. The remaining faint stars, which are more in number, will eventually drift apart and will no longer be visible as a cluster.
If you observe the image closely, you will see that the background is not uniform and it is noticeably streaked with dust. It has been speculated that these could be remnants of the cloud from which the cluster was found. If this were to be the case it would be truly remarkable, however it should be remembered that the Milky Way would have almost completed one full rotation during the life of the cluster and in this time there would have been a lot of reorganization, and hence this would most likely be a chance alignment of the stars and dust clouds. So, in all likelihood, the dust and gas from which Messier 7 was formed, and the star cluster itself would have disintegrated long ago.
The description given by Claudius Ptolemy all those years back was very apt since Messier 7, to the naked eye, does appear as a diffuse luminous patch against the bright background of the Milky Way. In his honour, Messier 7 is sometimes called Ptolemy's Cluster. Several other astronomers have also been fascinated by the Messier 7. In 1764 Charles Messier included it as the seventh entry in his Messier catalogue of comet like objects while in the 19th century, John Herschel observed this object through a telescope and described it perfectly by calling it a "coarsely scattered cluster of stars."
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