Wednesday, October 25, 2006

The Lion, the Moon and Saturn

The Lion, the Moon and Saturn
by Dave Adalian

Starting before dawn on Monday morning, the Moon will enter the belly of the beast.

In the early morning, around an hour or so before sunrise, the slender crescent of a waning moon will lie due east, sitting like a cosmic ball of yarn between the paws of Leo the Lion.

But, it won’t be alone. Just below and the to the right of the Moon will be the bright, yellow ringed planet Saturn, making it a cinch to find this second largest of the eight planets.

While it will seem the Moon and Saturn are so close they could reach out and touch one another, in reality the Moon is just 220,000 or so miles from Earth, while Saturn is more than 900 million miles away at present. And, while Saturn, a simple pinprick in the sky, seems much smaller than our 2,000-mile-wide Moon, it is actually 75,000 miles across.

In fact, Saturn’s rings are the largest structure in the Solar System besides the Sun itself. Measured side to side, Saturn’s ring system is an impressive 155,000 miles wide.

On Tuesday morning, a still thinner Moon will head deeper into Leo, sitting just below the lion’s brightest star, Regulus. The word Regulus is Latin for “the prince,” and is sometimes referred to as Cor Leonis, or the heart of the lion.

Regulus is a young, fast spinning star, making a complete revolution about every 16 hours, a spin so quick it makes the star bulge in the middle. And, while Regulus is a very bright first-magnitude star, it is actually 77.5 light years away.

By Wednesday morning, the Moon will have moved on again, its crescent growing smaller still as it leaves Leo and passes just to the right of the brightest star in Leo’s tail, Denebola, a name which means “tail of the lion” in the original Arabic.

While second-magnitude Denebola is not nearly as bright as Regulus, it is actually larger at 1.6 million miles wide compared to Regulus’ 1.4 million mile girth. It’s also closer, less than half as far away at 36 light years.

If Denebola is closer and bigger than Regulus, why does Regulus shine more brightly? Simply because it is hotter, its higher temperature making it shine 350 times brighter than our Sun. Cooler Denebola is a mere 12 times brighter than 865,000-mile-wide Sol.


Join the Tulare Astronomical Association for a look at the stars of autumn Friday, 7:30 to 9:30 p.m., at the Arthur L. Purcell Observatory, 9242 Ave. 182, south of Tulare and 2.1 miles west of Highway 99. Information and directions:


This column originally appeared in the Visalia (Calif.) Times-Delta and Tulare (Calif.) Advance-Register on Oct. 12, 2006.

No comments: