Last week in Starwatch I told you about how all of the stars in our sky, including our closest star, the sun, all appear to revolve around the North Star Polaris every 24 hours.

That’s because Polaris shines directly above Earth’s North pole. That makes Polaris the “Lynch Pin” of the sky. I’m sorry, I couldn’t resist.

In our Butler sky, Polaris is perpetually perched in our heavens just under halfway between the northern horizon and the overhead zenith. The Earth rotates on its axis once every 24 hours, which makes it look like the stars are circling around Polaris during that period.

That’s not the only movement of the stars in our sky. As our Earth orbits the sun every year, the Earth’s nighttime side faces different directions toward space. That’s why we see different constellations from season to season. That adds to the fun of stargazing!

As all of the stars appear to circle Polaris because of Earth’s rotation, they also shift a little to the west from night to night as the Earth orbits the sun. Specifically, they shift one degree west, or about the width of one of your fingers held at arm’s length.

Certainly that tiny shift is hard to detect from one night to the next, but over just a few weeks, you start to notice the westward migration. Over the course of a month or two, observing at the same time of night, you’ll eventually see “new” constellations emerge from the eastern horizon while you start losing constellations below the western horizon.

Stars and constellations in the eastern sky rise about four minutes earlier every night, while stars in the western heavens set four minutes earlier. The entire cycle of this night to night migration takes one year. In the diagram, you can see how the bright constellation Orion shifts westward in the evening sky every year.

In the northern sky, the circumpolar constellations never rise or set. Instead, they shift one degree in a counter-clockwise direction around Polaris from night to night. That’s why the Big Dipper appears upright in the very low northern sky in the late autumn, and appears upside down in the high northern heavens in late spring.

The Earth’s orbit around the sun, combined with its rotation around its axis, brings the old adage “the early bird gets the worm” into play. The early bird also gets a head start when it comes to stargazing. The constellations visible in the pre-morning twilight sky at any given time are the same ones seen in the evening about four months later.

For example, we see the same arrangement of constellations just before the early morning twilight in March and April that we will see in July in the evening twilight. You can get a jump on evening summer stargazing this time of year by setting the alarm and getting out under the heavens.

If you’re up and at ’em in the early morning, in the low eastern morning sky you can see a really bright star on the rise. That’s no star but the gargantuan planet Jupiter.

With a small telescope, you can spot up to four of Jupiter’s moons as they orbit around the big guy of our solar system. Jupiter’s moons will appear in a diagonal line on both sides of the planet. You might also see some of Jupiter’s cloud bands.

The next brightest “star” to the upper right of Jupiter is Saturn. With a small telescope, you should be able to see Saturn’s famous ring system.

If you need your beauty sleep and don’t want to wake up that early, wait until August, and you’ll see Jupiter and Saturn in the evening eastern sky as the Earth trods along in its orbit around the sun.

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.