Tuesday, June 13, 2006

Solstice Marks Summer's Start

Solstice Marks Summer's Start
by Dave Adalian

Soaring temperatures may make it seem like summer has already arrived, but even so the astronomical start of the season is still nearly a week away.

Summer, according to astronomers, begins with the solstice, the moment when the Sun reaches the northernmost point above the celestial equator, an imaginary line above Earth’s equator that divides the sky into northern and southern hemispheres.

The solstice is also marked by the rising and setting of the Sun as far north on the horizon as it can reach. If you watched the sunrise each day, you’d notice the Sun swings back and forth slowly along the horizon until it reaches its northernmost point in June and its southernmost point in December. Solstices mark the days when the Sun stops then reverses direction. In Latin the word solstice literally means Sun (Sol) stands still (sistere).

The Sun will reach the summer solstice on Wednesday at 5:26 a.m., just a few minutes before it rises, and summer 2006 will be underway.

Even if you didn’t have the Sun to set your calendar by, the stars could serve in its stead.

It’s a sure sign spring is at an end when the constellation Leo is standing on its head above the western horizon just after the Sun goes down. Find it by looking for the backward question marking the lion’s head and the triangle of stars that is its haunch.

Looking north, the Big Dipper of Ursa Major is propped up with its handle high in the air. Following the curve of its tail and extending it past the end of the handle and across the zenith takes us to bright orange Arcturus in the constellation Bootes. This star is the brightest in the summer sky and the northern hemisphere.

After arcing to Arcturus, continue along the curve from the Dipper and speed on to Spica, the brightest star in the Virgo. Don’t make the mistake of confusing Spica with bright Jupiter which sits just up and to Spica’s left.

The eastern sky holds a trio of bright stars so tied to summertime the shape they draw is named after the season. Deneb in the north, Altair in the south and Vega above them form the Summer Triangle. One of the brightest portions of the Milky Way spills through the center of the triangle and is visible even from urban backyards. For an even better view, head for the darker skies outside the city.


This column originally appeared in the Visalia Times-Delta on Thurs., June 15, 2006.

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