Sapphire Star Cluster: The Pleiades
Quick Facts:
The Pleiades is an open star cluster located in the constellation Taurus
It is also known by many different names, including: Messier 45, The Seven Sisters Cluster, and Subaru in Japan (the Subaru car brand logo depicts the cluster)
Easily visible to the naked eye, The Pleiades has a rich mythological history dating back to ancient times
A Tale of Seven Sisters: A Historical Background
The Pleiades is one of the closest star clusters to Earth, located only 445 light years away. Easily visible with the naked eye, this cluster of stars has captivated humans since ancient times, sparking a sense of curiosity as we gaze upwards and contemplate the universe. Historians have found mention of this star cluster from seemingly every ancient civilization who were at latitudes able to view it; including the Maori and Australian Aborigines, Chinese, Maya, Aztec and indigenous North Americans.
The Pleiades likely derive their name from the ancient Greek verb plein, meaning “to sail”, as the rising of the cluster in the night sky marked the start of the navigation season. It is believed that the Greek myth followed; where the stars visible to the naked eye represent the seven daughters of Atlas and Pleione: Alcyone, Maia, Electra, Taygeta, Asterope, Celaeno, and Merope. The cluster is sometimes referred to as The Seven Sisters for this reason.
In the early 1600’s, The Pleiades was viewed for the first time through the lens of a telescope by Galileo. In his book Sidereus Nuncius (Sidereal/Starry Messenger), Galileo sketched the cluster and noted that there were many more stars present than what the naked eye could perceive.
The Nebra Sky Disk, an Early Bronze Age artifact depicting the Pleiades cluster in between the sun and moon, circa 1600 BCE
Source: Wikimedia Commons
Galileo’s Sidereus Nuncius sketch of Pleiades, humanity’s first look at the cluster using a telescope.
Source: History of Science Collections, University of Oklahoma Libraries, Pleiades Sidereus Nuncius, CC BY 1.0
A Modern Understanding
Today, we know there are over a thousand stars that make up the cluster, with many more hidden binary or multiple star systems awaiting discovery. The Pleiades is composed of relatively young stars, born around 100 million years ago during the age of the dinosaurs in the Cretaceous Period.
The Pleiades formed from a molecular dust cloud that collapsed under its own weight, caused by gravity. As these newly formed stars ignited and radiated light outward, the energy propagated through the dust causing more stars to form. It was previously thought that the dust visible in this image was a remnant of the cluster's birth; however, the current theory is that the cluster is passing through a particularly dusty patch of the interstellar medium.
Where & When to See Pleiades
The Pleiades Cluster is visible if you are located north of the antarctic circle. Even in cities with a high amount of light pollution, the cluster is visible if you know where to look. I recommend downloading a stargazing app on your smartphone to let it point you to the location in the sky. I personally use Stellarium.
If you’d like to view the Pleiades immediately after dusk, January and February will be the best month to find it, as it will be at its highest point in the night sky after sunset.
If you’re an astrophotographer and want to maximize your viewing time, you should plan to image during November or December.
