Astronomy: An upcoming solar eclipse and Saturn, too


Tom Burns - Stargazing



On August 21, Central Ohio will bear witness to a partial eclipse of the sun by our celestial neighbor, the moon. The eclipse will begin at 1:04 p.m. as a tiny bite as Luna passes in front of the sun. The bite will increase as eclipse continues toward maximum coverage at 2:35 p.m. when just over 80 percent of the sun will be obscured. After that moment, the sun will appear increase in size until about 4 p.m. when the sun will appear normal again.

Over a narrow path stretching from Oregon in the west through some western states to Tennessee, Kentucky, and South Carolina, the sun will be obscured entirely for just over two minutes. During that brief time, with the sun’s bright disk obscured, the sun’s outer atmosphere, called its corona will be easily visible to the unaided eye.

Such total solar eclipses are rare, and if you have the time and the inclination, it might be worth taking a drive down to the eclipse path.

The two-minute period of totality is the only safe time to look at the sun without some sort of observing protection. Otherwise, it is never safe to look at the sun unless you are using the right kind of protection. I’ll be discussing such solar-safe observing methods in the coming weeks.

The best method to observe the partial phases of the eclipse (and to observe the sun any time) is to purchase a pair of eclipse glasses. I keep a pair with me everywhere I go to look for naked-eye sunspots. I have been using them for decades with no apparent damage to my eyes.

Perkins Observatory is selling its solar glasses though the five locations of Half Price Books in Central Ohio. We’re also including two brochures with detailed information about this eclipse, solar eclipses in general, and alternative, safe ways of looking at the sun.

We’ll also be discussing the solar eclipse and observing the sun with solar-safe telescopes at our annual Celebration of the Sun programs on July 8, 16, and 22 starting at 4 p.m. Call 740-363-1257 for details and to arrange tickets.

Get ready for Saturn

The most spectacular sight in a telescope is Saturn and its fabulous rings. In the coming weeks, Saturn is well placed to provide such a view.

Binoculars won’t help you here. Saturn is huge, but it is also really far away as planets go. However, even a small telescope will show its fabulous ring system.

Look to the southeast after it’s good and dark. Saturn is the bright, yellow “star” at the feet of Ophiuchus, the Serpent Bearer.

In late July, Saturn reaches its highest point directly south around 10 p.m.

At 75,000 miles in diameter, Saturn is the second largest planet after Jupiter, and at 885 million miles away, it’s the farthest from the sun of all the planets visible to the unaided eye.

It takes more than 29 years for Saturn to orbit the sun. During the average human life, it makes no more than three such trips. For that reason, Saturn moves very slowly against the background stars of the zodiac. (Yes, Ophiuchus is a zodiacal constellation. Please pass that on to any astrologers you may be acquainted with.)

Saturn averages about 240 degrees below zero on its surface, but it really cannot be said to have a surface. Like most of the outer planets, Saturn is, on the surface at least, a great gasbag.

Like Jupiter, underneath its dense atmosphere, it is mostly composed of liquid hydrogen, with a smattering of helium, ammonia, and methane ice crystals thrown in.

Saturn is thus not a very heavy planet. If you could arrange a pan of water big enough, Saturn would float!

Saturn’s gassy surface doesn’t show much detail, but look for the shadow of the rings as a curved dark band projected on the planet.

And look for a dim point of light just outside the rings. You’re seeing Titan, biggest and brightest of Saturn’s two dozen or so moons. At 3,500 miles in diameter, Titan is bigger than the planet Mercury.

Okay, now look at the rings. This year, they are tilted in such a way as to expose their structure well. They look like a rakishly tilted hat brim.

Over the next few years, the rings will slowly tip over. In six years, they will look like a line cutting the planet in half.

The rings you can see in a ‘scope are about 170,000 miles in diameter, more than twice as wide as the planet’s disk.

But close-up views from the Voyager spacecraft reveal fainter outer and inner ring segments invisible from Earth.

The outer rings extend out to a diameter of 600,000 miles. The inner rings float a mere 5,300 miles from Saturn’s cold cloud tops.

Despite their enormous width, the rings are extraordinarily thin, ranging from a scant 30 to 500 feet thick.

Although the rings look solid in a telescope, they are really mostly composed of jagged pieces of water and ammonia ice that probably average no more than a few feet in diameter.

The pieces aren’t very closely packed together either. When Saturn passes in front of a star, the star is usually visible through the rings.

My earliest astronomical memory is the view of Saturn’s rings through a neighbor’s telescope. That single view sparked a lifelong interest in astronomy.

A whole generation of children is waiting to be delighted in the same way. If you have a telescope, take them out and give them a look.

Starting with our Friday-night programs on July 28 and through August, we will feature Saturn in our telescopes. Call 740-363-1257 for details.

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Tom Burns

Stargazing

Tom Burns is director of the Perkins Observatory in Delaware.

Tom Burns is director of the Perkins Observatory in Delaware.