This week’s challenge is a longstanding rite of passage for amateur astronomers. It is also a quick and easy way to gauge the quality of a night’s observing conditions whenever the constellation of Taurus, the bull, is visible.
It involves counting the number of stars in the Pleiades. One of only a handful of star clusters visible to the naked eye, the Pleiades is particularly special because we can resolve some of the stars that makes it up. Another name for the cluster is the seven sisters – but that doesn’t necessarily mean that you can see seven stars.
The chart shows the Pleiades’ location, above the shoulder of Taurus, with Alcyone the brightest star in the cluster. Even a casual observer should be able to see five stars from a reasonably dark site. It takes a little effort and patience to see more. On good nights, when conditions are clear and the air is still, up to five more members of the central cluster can be glimpsed.
Advanced observers can also find online charts to start hunting the fainter, outlying members of the cluster. But for most, seeing between five and 10 is good.
