Mike

Everyone knows that the sun is the brightest star in the sky, but do you know what the second brightest is?

If you said Polaris, you're wrong — but don't feel bad because that's what many people think. Polaris is actually 40th.

The second brightest star seen from Earth is Sirius, a star in the winter constellation Canis Major, the Big Dog.

Even though Polaris, otherwise known as the North Star, is only the 40th brightest star, it's a very important one.

The best way to find Polaris is to use the Big Dipper. The Dipper is very high in the northern sky this time of year, nearly upside down.

Draw a line in your mind's eye between the stars Merek and Dubhe on the side of the pot section opposite the Big Dipper's handle. Continue that imaginary line downward from Dubhe, and it will come very close to pointing at Polaris. If you make a fist at arm's length, three fist-widths will get you to Polaris. Try it. It really works!

Polaris is what I call the "Lynch" pin of the heavens. Okay, that was bad. Polaris appears stationary from our vantage point on Earth, so every celestial object in the sky — every star, planet, moon, sun or anything else — appears to circle Polaris every 24 hours.

Because the North Star shines directly above the Earth's terrestrial North Pole, we see a reflection in the sky of the Earth's rotation. We certainly can't feel the Earth's rotation, but we sure have visual evidence. By the way, we're spinning at better than 700 mph at our latitude here in Butler.

At our latitude, about 41 degrees north, Polaris is 41 degrees above the horizon or just about half way from the northern horizon to the overhead zenith.

Constellations close to Polaris, including Ursa Major, which the Big Dipper is part of, Ursa Minor, Cassiopeia, Cepheus, and a few others, are also above our horizon as they whirl around the North Star.

If you were to travel north, deep into Canada, Polaris would be higher in the northern sky, and you would have more and more circumpolar stars the farther north you travel. If you were to travel into the southern U.S. and Mexico, Polaris would be lower in the northern sky, and you'd have fewer circumpolar stars.

All other stars in the night sky that aren't close enough to Polaris to be circumpolar stars are called diurnal stars. They also appear to circle the North Star, but dip below the horizon during their circuit. So, just like the sun and the moon, they rise in the east and set in the west.

The 24-hour journey around Polaris isn't the only dance most stars make. They also shift slightly to the west, about one degree each night, due to the Earth's orbit around the sun. As Earth orbits our home star, the nighttime side of the Earth faces different directions in space from week to week, month to month, and season to season.

There is an easy way to prove that shift to yourself. Find a place with a low horizon and a spot where you can line up a bright diurnal star that's low in the sky with a prominent land structure like a church steeple or flag pole. Mark the spot where you are standing and note the time to the minute. Go out the next clear night and stand in the same spot at the same time, and you should easily see the westward movement.

Because of this night-to-night westward shift, over time, the stars and constellations you see get lower and lower in the western sky, and the stars in the east rise higher and higher. That's why we have different constellations in the evening from season to season.

For instance, we still have winter constellations in the evening sky like Gemini the Twins and Auriga the Chariot Driver in the west setting earlier and earlier, while summer constellations like Cygnus the Swan and Lyra the Harp are rising earlier and earlier each evening.

There is yet another motion to consider. The Earth's axis between the North and South Pole is slowly wobbling. Because of that, Polaris will not always be our North Star, but that's a long time in the future!

Celestial Happening this week: Among the parade of stars in the early evening western sky will be the very bright planet Venus, much dimmer Mars, and the new crescent moon. The moon will pass by both worlds this coming week, making for some lovely celestial conjunction or what I like to call "celestial huggings." On Tuesday night, May 23, the moon will be just to the upper left of Venus. That should be a stunning view! On Wednesday, May 24, a somewhat fatter crescent moon will be perched above Mars. Even without a telescope you can easily see the planet's reddish hue even though it's about 177 million miles away. Next month Mars and Venus will have a great celestial hugging. Stay tuned!

Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is the author of "Stars: a Month by Month Tour of the Constellations," published by Adventure Publications and available at bookstores and adventurepublications.net. Contact him at mikewlynch@comcast.net.