(Continued from page 5)

to our sun, these stars are all significantly younger, larger and hotter. They are all about 400 light years away, and are bound to each other by gravity.
• Why is the Pleiades star cluster called the Seven Sisters?
• Even if you are familiar with the Pleiades, or Seven Sisters, you may think that it is just a winter delight. The Pleiades are visible in the evening in a Northern Hemisphere winter.
• Yet, like all other stars, these are to be seen in the morning sky just as much as in the evening sky, even though not at the same time of year. In fact, if you know when and where to look, the Pleiades cluster is visible to some extent every night of the year from about mid-June until early the following May, when the sun comes between us and this cluster. This is not strictly true everywhere on Earth, however, because visibility of the Pleiades is more restricted in the Southern Hemisphere (it can't be seen at all in Antarctica), and complicated in north polar regions due to long periods of daylight. For several weeks before and after May 20, the sun is located too close to the Pleiades along our line of sight for the cluster to be seen easily.
• July 2012 guide to the five visible planets
• But for many of us in the Northern Hemisphere, the Pleiades cluster is a harbinger of cooler weather, since it is first seen in the early evening sky in October. So to view these Pleiades stars during the heat of July is a welcome confirmation that this season, too, shall change. Wake up early tomorrow, to see the moon by the Pleiades cluster, and the Pleiades lining up with the brilliant planets Jupiter and Venus.
•