NASA Astronomy Picture of the Day 5 January 2023: The Pleiades Star Cluster

Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. They are celestial objects millions of years old floating in space. The older and bigger the star, the brighter it appears. They are formed in star-forming regions called Nebulae. The makeup of a Nebula consists of gases, mainly hydrogen and helium. After formation, many stars form groups from the same Nebula, which is known as a Star Cluster. According to NASA, Star clusters can contain as few as ten stars or as many as millions of stars.

NASA’s Astronomy Picture of the Day is of the Pleiades Star Cluster with its striking blue reflection. It is one such star cluster which is located approximately light-years from Earth in the constellation Taurus. It is an open star cluster which contains over a thousand stars that are loosely bound by gravity. Pleiades is also known as the Seven Sisters as its name has been derived from the famous Greek legend where the Pleiades are the 7 daughters of the Titan god Atlas and the ocean nymph Pleione. Therefore, their names along with their daughters’ make up the 9 brightest stars in the star cluster.

The image was captured by Stefan Thrun who is an astrophotographer and astonishingly, a former German Air Force Soldier.

NASA’s explanation of the picture

Hurtling through a cosmic dust cloud a mere 400 light-years away, the lovely Pleiades or Seven Sisters open star cluster is well-known for its striking blue reflection nebulae. It lies in the night sky toward the constellation Taurus and the Orion Arm of our Milky Way galaxy. The sister stars are not related to the dusty cloud though. They just happen to be passing through the same region of space. Known since antiquity as a compact grouping of stars, Galileo first sketched the star cluster viewed through his telescope with stars too faint to be seen by eye. Charles Messier recorded the position of the cluster as the 45th entry in his famous catalog of things which are not comets.

In Greek myth, the Pleiades were seven daughters of the titan Atlas and sea-nymph Pleione. Their parents’ names are included in the cluster’s nine brightest stars. This well-processed, color-calibrated telescopic image features pin-point stars and detailed filaments of interstellar dust captured in over 9 hours of exposure. It spans more than 20 light-years across the Pleiades star cluster.