Don’t look now…but there’s something like an eclipse of the sun underway. The planet passing in front of the solar disk is Mercury, a heavenly body so small we won’t notice any dimming of the sun’s light but Drake University Astronomy Professor Charles Nelson says people ARE keeping an eye on the event.

It’s called a “transit,” he says, but since Mercury’s only one two-hundredth the size of the sun, it’ll only cover a tiny part of the sun and will be difficult to see even with a telescope. He says anybody who’d like to get a look could use a small home telescope but the professor cautions that you must have a good solar filter.

Nelson says the study of the transit has provided good data. There was a time when scientists still figuring out the orbit of Mercury watched to see just when it contacted the edge of the sun’s image. These days those facts are well known, so the purpose of watching the transit is just passing interest. And while we gaze at photos of Jupiter and Saturn captured by long-range space probes, Nelson says those unmanned space ventures also send home snapshots of the small planet closest to our sun.

Typically what happens is that a probe destined for the outer solar system is aimed inward, to get a “slingshot” effect by circling the sun as its journey begins. It’ll take pictures along the way and so we have many photos of Mercury, which looks like our moon, dry and cratered. Nelson says it’s just a little larger than the moon of earth. The transit began a little after one this (Wednesday) afternoon, and will go on until sundown.