April star of the month: Vindemiatrix

Vindemiatrix is the third brightest in the constellation Virgo following brighter Spica and Porrima. It's in the Western skies in the evenings now. The planet Saturn is not far away.

The name is a somewhat corrupted feminized Latin form for the original Greek name that meant "the Grape Gatherer," as the first visibility of the star in morning light after the Sun cleared out of the way (the "heliacal rising") told rural people in the Roman Empire that it was time to pick the grapes.

Vindemiatrix is a somewhat unusual star, a middling temperature yellow class G giant only a bit cooler than the Sun. As a giant, however, it is considerably brighter than the Sun. From its temperature and distance of 102 light years, its luminosity is 83 times solar, these combining to give a radius 12 times that of the Sun, all similar to the brighter, cooler component of Capella.

The star seems to be a about 15 percent richer than the Sun in metals, and is somewhat distinguished by having most of its motion in the direction perpendicular to the line of sight, making it appear to move rather rapidly against the background stars, a second of arc in five years.

Much more significantly, Vindemiatrix is a rather powerful X-ray source, implying considerable magnetic surface activity. Its total X-ray radiation is almost 300 times that of the Sun, ranking it third among nearby cool single giants and beat out only by Deneb Kaitos which lies northeast of the bowl of the Big Dipper.

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