All around the North Star and a visit from a comet
When you ask the average person what the brightest star in the night sky is, there’s a good chance many will say it’s Polaris the North Star.
For sure it’s a moderately bright star, but there are 50 other stars in our heavens that can brag that they’re brighter. Sirius is the brightest nighttime star. The brightest star in the constellation Canis Major, the Big Dog, still barely visible in the low early evening southwestern sky.
While Polaris is far from the brightest, it’s an important star because it shines directly above the Earth’s North Pole. Polaris is perched 433 light-years, or just over 2,500 trillion miles, above the North Pole.
The light that we see from Polaris tonight left that star when the famous astronomer Galileo Galilei was only 29 years old! Polaris is also a huge star, kicking out more than 2,500 times more light than our sun.
Since Polaris shines directly above the North Pole, all of the other stars in our sky, including the sun and moon, appear to revolve around Polaris once every 24 hours. Of course it’s not the stars that are moving, but rather the Earth rotating on its axis with all of us along for the ride.
If you were standing on top of the world at the North Pole, Polaris would be directly over your head. You’d see all of the other stars obediently revolving around it. None of the stars would rise or set. We would see the same set of stars night after night and season after season.
Since we’re living in Pennsylvania, about halfway from the North Pole to Earth’s equator, the North Star is not overhead, but fixed about halfway from the northern horizon to the overhead zenith. Polaris is easy to find with the help of the nearby Big Dipper. This time of year, the Big Dipper, which serves as the rear end and tail of the constellation Ursa Major, or the Big Bear, is hanging nearly upside down in the high north-northeast sky.
The two stars that mark the side of the dipper’s pot section opposite the handle, Merak and Dubhe, act as pointer stars to Polaris. Just draw a line from Merak to Dubhe and continue that line beyond Dubhe, and it will go almost exactly to Polaris. The North Star is about 30 degrees from Dubhe, or roughly three of your fist-widths held at arm’s length.
No matter what time of night or year, wherever the Big Dipper is in the northern sky, the stars Merak and Dubhe will always point at Polaris. Along with being the “lynchpin” of the heavens, Polaris also serves as the brightest star in the much dimmer Little Dipper, the nickname for the constellation Ursa Minor, the Little Bear.
Constellations close to Polaris, like Ursa Major and Minor, as well as Cassiopeia the Queen and Cepheus the King, make a tight daily circle around the North Star. Because they’re so close to Polaris they never set below the horizon. They graze the northern horizon at their lowest point. These Polaris-huggers are better known as circumpolar stars.
The rest of the stars, farther away in the sky from Polaris, also circle the North Star once every 24 hours, but the northern portion of their circles lay below the northern horizon. So to us, those stars rise at some point in the east and set at some point in the west, just like the sun and moon.
Not only do all of the stars circle Polaris every single day and night, but they also shift to the west a little bit each night. That’s a good thing, because that means we see different constellations from season to season through the course of the year, because Earth orbits the sun.
This weekend, caught up in stars circling Polaris is a comet possibly bright enough to barely see with the naked eye, especially away from urban light pollution.
Comets are dirty cosmic snowballs that partially melt and form a tail as they near the sun. This one is formally known as Comet C/2025 R3 PANSTARRS, or Comet Panstarrs for short. It was discovered last year.
This weekend, it reaches its closest approach to the sun as expected to survive, according to most astronomers. If it approaches this coming week, we might have a comet bright enough to see with the naked eye, and its fairly long tail.
I have to warn you though from experience, comets are like house cats — they both have tails and do whatever they please. Fingers crossed!
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is also the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and at adventurepublications.net. Contact him at mikewlynch@comcast.net.
