This week I’m sure you’ll hear in the media that we’re having a “supermoon” on Saturday night, one of three happening this year.

A supermoon is a full moon that happens to occur when the moon is within 224,641 miles of the Earth. If you think it’s an arbitrary number, you’re right.

That distance was set not by scientific astronomers, but rather by non-scientific astrologers.

There is some connection with actual astronomy because the moon’s orbit around the Earth is not a perfect circle, but rather a slightly oval shaped ellipse.

That means the moon reaches it closest approach to Earth at 225,804 miles and its maximum distance from Earth of 251,968 miles every month.

There’s no question the full moon later this week will be a little larger in the sky, but not as much as it will be hyped up to be.

In November we’ll have another “supermoon,” the closest one of the year. I’ll have more next month in Skywatch.

In the meantime, this week I want to feature a bright star that we’re destined for, Vega.

As soon as it is dark enough these Butler October evenings I want you to look for the brightest star you can see in the very high western sky, not far from the overhead zenith.

That’s Vega.

Actually, right now it’s the second brightest star in the entire celestial dome in the early evening. The only one brighter is Arcturus in the very low western sky. So how do you pronounce Vega?

Some say “VAY-gah,” like the old, ill-fated Chevrolet car in the 1970s, but others insist that it’s “Vee-ga.”

That is actually the proper pronunciation, but most people I know, including yours truly, pronounce it just like the old Chevy.

However you say it, Vega is a significant star, not so much because of the star itself but because of where it is in our night sky.

Vega is a star that is about twice as massive and twice the diameter of our sun, making it almost 2 million miles in girth. Its surface temperature of 17,000 degrees Fahrenheit is about twice that of the sun.

The main reason it’s so bright in our sky is because it’s relatively closer than most stars you see at a glance, although it’s not exactly a weekend trip away.

Vega is around 25 light years away, with just one light-year equaling nearly 6 trillion miles.

A light-year is defined as the distance that light travels in a year, so at 25 light years the light we see from Vega tonight left that star when George H.W. Bush was our president in 1991.

Vega also spins on its axis crazily every 12 hours. If it was spinning just a little faster it would break apart.

By comparison, it takes our sun about a month to make one rotation. The axis of Vega is also perpendicular to our sun, so if you lived on Vega our home star would be its “North Star”

What really makes Vega significant for us is that it marks the direction of what astronomers call the solar apex. That’s the direction in which the Sun is traveling through space as it orbits around our Milky Way galaxy.

Our sun is just one of about 5 billion fellow stars in the spiral shaped galaxy that spans 100,000 light years in diameter.

The Sun is dragging the Earth and the rest of our solar system in the general direction of Vega at a breakneck speed of just under 140 miles per second.

We, of course, can’t feel the motion because it’s a constant speed, like cruising in a jet airliner.

Even though we are tearing along at half a million miles an hour, it will still take about 225 million years to make just one orbit around the center of our home galaxy.

So when someone asks you just where this world is really going, take them out to your backyard and point them in the direction of Vega.

Vega isn’t moving quite as fast around the Milky Way, so in about 60,000 years, give or take, it’s estimated that our sun and solar system will pass by Vega. We’re certainly not going to collide with Vega, but we will be almost twice as close as we are now at around 13 light years away.

After that we’ll start seeing Vega in our rear view mirror. I wouldn’t wait up for that because Vega won’t be much brighter than it is now in our sky, but hey, isn’t it nice to know where we’re all going, at least for another 60,000 years.

Celestial hugging

The planets Jupiter and Mercury are very close together in the very low eastern sky in the early morning twilight. Look about 40 minutes before sunrise.

Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul and is author of the book, “Stars; a Month by Month Tour of the Constellations” published by Adventure Publications and available at bookstores at www.adventurepublications.net.