Go outside after dark and look to the east and something will catch your eye. If it’s star-like and high in the sky, it’s probably reddish Mars. Look slightly lower in the sky, due east, and you’ll find a fainter, fuzzier object called the Pleiades (pronounced ‘player-deeze’).
The Pleiades are your new favorite object in the night sky.
This week they reach their highest point in the south—they culminate—at midnight. So if you do want to make astronomical observations come back at midnight with your telescope. For most of us that’s not particularly important, but what is worth knowing is that the Pleiades—also called the “Seven Sisters” and M45—are now at their best.
As the “best” celestial sight of all, in my opinion, the culmination of the Pleiades is something to celebrate. So here’s everything you need to know about the Pleiades, including how to find them, observe them, and exactly what you’re looking at.
What are the Pleiades?
They’re one of brightest star clusters in the sky and easily the most impressive star cluster it’s possible to see with naked eyes.
Around 444 light-years from the Solar System, the 3,000 hot B-type blue stars of the Pleiades are thought to be about 100 million years old, which makes them almost newborns, cosmically-speaking.
If that doesn’t ground you, I don’t know what will.
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What is an open cluster?
It’s a building block of galaxies. When giant molecular clouds collapse under the force of their own gravity, stars are born. The result can be a cluster of hundreds or even thousands of stars that initially move together through a galaxy—as the stars of the Pleiades are doing right now—until very slowly the stars disperse across the galaxy.
How to find the Pleiades
Look east after dark. That’s it! Another way is to locate Orion’s Belt, which will rise low in the northeast after dark. Trace an imaginary line from Orion’s Belt going up and to the right. The first bright star you come to is orangey Aldebaran, the brightest star in the constellation of Taurus. Go the same distance again and you’ll come to the Pleiades. That’s surely the most important star-hop in stargazing—and it’s why stargazers in the northern hemisphere love fall and winter.
What do the Pleiades look like to the naked eye?
Like a smudge in the night sky. Like a cloud of stars. A fuzzy patch. Whatever your first impressions of the Pleiades, have another look, and this time study them more carefully. You’ll see five or six (or possibly seven) stars in the rough shape of a mini-Big Dipper. The Pleiades are often known as the “seven sisters” in some ancient cultures; presumably they had keener eyes, or darker skies.
The Pleiades and the Hyades
Visually very close to the Pleiades are the Hyades, a much older star cluster that’s much closer to the Solar System. The closest star cluster to us at just 150 light years, the Hyades can only really be appreciated with the naked eye since the stars are spread-out across a larger area of the night sky.
To find the Hyades, just locate Aldebaran—an orange supergiant star that’s merely in front of the Hyades, not part of it. The stars of the Hyades are all around Aldebaran.
What’s the best way of looking at the Pleiades?
You’ll notice that finding more than five individual stars within the Pleiades is tricky, but if you look just to the side of them rather than straight at them, the whole cluster looks so much brighter. This is the “averted vision” technique, which works because your eyes have cones that are sensitive to color and rods that are sensitive to brightness. The rods are in your peripheral vision, which is why you can “see” the Pleiades’ collective brightness better if you don’t look directly at them.
What do the Pleiades look like in binoculars?
Although careful observing pays off for the Pleiades, the best way to look at these stars is through any pair of binoculars (10×50 work really well, but any magnification works well). You’ll be able to make-out the individual stars much more easily—and you’ll see up to about 30.
The nebulosity between the stars of the Pleiades—consisting largely of light reflecting off the leftovers of the same molecular dust clouds that collapsed to form the stars—can be seen in a long exposure photograph (see above).
What’s the brightest star in the Pleiades?
Alcyone, which is actually two giant hot “B” stars, with one of them having three smaller stars in orbit. Alcyone is 2,400 times as luminous as our Sun.
Why are the Pleiades so special?
What makes the Pleiades really special to stargazers is that they are really bright and they’re visible to everyone on the planet for six months of the year. Perhaps that’s why they have made such a mark on popular culture. As well as being known to most indigenous cultures, did you know that Subaru is the Japanese name for the Pleiades, which inspired the Japanese car company’s logo?
The Pleiades and Venus
The planet Venus passes close to the Pleiades every eight years. The last time was April 3, 2020 when they were imaged by thousands of astrophotographers. The orbits of Venus and Earth are in a near-resonance, so both return to nearly the same positions in the Solar System every eight years. The next close encounter of Venus with the Pleiades is in 2028.
One of the jewels of the northern hemisphere’s night sky in winter, the Pleiades are at their best right now, so go take a look. You’ll be looking at them with wonder for the rest of your life.
Wishing you clear skies and wide eyes.