Seven Sisters, Count Them

As winter fades, so do the Pleiades. It’s best to catch the singularly sublime "Seven Sisters" before Mother Nature and Father Time send their sun back to Pisces for the spring equinox.

The star cluster officially known as M45 is found in the constellation Taurus. This week, stare high in the southwest at approximately 8 pm. The later at night and/or the later in the week you look, the farther west you should turn. As with the sun, moon, planets and all zodiac constellations, Taurus rises in the east, sets in the west and takes approximately 12 hours to complete its journey. Each night, it rises four minutes earlier than it did the previous night. So each night becomes a microcosm for the season.

Once we find ourselves fully in the swing of spring, we will find that Taurus has set before any healthy star-gazing hour.

In order to locate the Pleiades, perhaps the most helpful landmark is Orion — particularly his belt. If you are familiar with this prominent winter formation, then direct your gaze to the right (and slightly up) approximately three fist-widths from the belt until you find the bright V-shaped snout of Taurus the bull. To the right of this V, less than a fist away, sits a formation that is unmistakable once your naked eyes land on it. It is both literally and technically a "cluster" of stars — seven of which are visible without equipment on a crisp March night.

Named by ancient Greek astronomers for the seven daughters of Atlas and Pleione, these bright, beautiful stars are glued together by something more than our terrestrial perspective. Many stars appear next to one another on the inner surface of our sky dome, but turn out to differ by light centuries in their distances (or depth) from Earth. The contents of a cluster such as the Pleiades, however, are actually gravitationally tethered. They are a physical system. The core of the Pleiades is approximately 440 light years from Earth.

First, it means that the 2.6 quadrillion miles that separate us from them require Pleiadean light to take 440 years to get here. So when we say that the Pleiades are beautiful, we really mean that the Pleiades of late medieval times were beautiful. We have no idea what the Pleiades, if still in existence at all, have looked like since the day Pope Gregory XIII placed us on the first page of our current calendar.

Second, it means that the Pleiades constitute one of the star clusters closest to Earth. This one happens to be what is known as an open cluster — one consisting of relatively few (hundreds) relatively young stars (tens of millions of years old) living in a relatively tight radius (tens of light years).

Of all the known star clusters, M45 is the most obvious to the unaided eye. If you do choose to check it out through binoculars or a telescope, then try to keep your lenses around for the last week of March. At that time, expect a special visit. The dwarf planet Ceres will pass roughly 10 moon widths below the seven sisters.