More than a thousand years before Copernicus, the Greek astronomer Aristarchus postulated that the sun was at the center of the solar system, not the Earth. He lived 23 centuries ago between 310 and 230 B.C. Yet if Aristarchus could stand under tonight’s night sky he would see virtually the identical constellation patterns as we do. Only two bright, obvious stars would have shifted their positions — Sirius and Arcturus. And you’d have to be a keen-eyed observer to notice. Since Aristarchus’s time they’ve moved about 1° to the southwest — only the width of your little finger held at arm’s length.
In truth, the stars are clipping along at multiple miles per second but only appear to move slower than molasses at the South Pole because they’re so far away. For that reason we can count on the constellations to look the same over many lifetimes, but in the grand scheme of time — we’re talking tens of thousands of years — all the current constellations will dissolve into new patterns as the sun and our stellar neighbors circle around the center of the Milky Way.
So does that mean it’s impossible to see a star move in your lifetime? Thankfully, no. While none of the brighter stars is close enough and fast enough to show motion, there’s one little luminary that does called Barnard’s Star. It’s named for American astronomer Edward Emerson Barnard. In 1916 he measured its motion relative to the sun (called proper motion) and discovered it was speeding across the sky at the rate of 10.3 arc seconds a year or half the apparent diameter of the full moon over the course of a human lifetime.
Barnard’s star is also only 6 light years from Earth, making it the fourth closest star after the sun and the Alpha Centauri triple system. It’s also tiny with a diameter just twice that of Jupiter and a mass only 14 percent that of the sun. Located in Ophiuchus the serpent-bearer this red dwarf shines at magnitude 9.5. While too faint to see with the eye it’s an easy catch in a small telescope.
Several other telescopic stars move fast enough to see move in a lifetime but none faster than Barnard’s. Many of the stars we see in the night sky travel together along with the sun in a general stream around the galaxy’s hub, but Barnard’s Star is both close and moving at an angle relative to the sun, the reason it appears to zip across the sky.
I first tracked this glowing ember down on a muggy July night 1987 while battling hordes of mosquitos. Pencil in hand and red light in mouth I carefully sketched its position relative to neighboring stars in the field of view. Funny thing. I intended to return a year or two later — the amount of time I figured it would take to detect its motion — but didn’t get back until a week ago! How time flies. So did Barnard’s Star. In 33 years it had moved a fifth the apparent diameter of the full moon to the north. Wow! The shift was incredibly obvious.
I had finally succeeded in seeing a star move. And it got me thinking about all the life I’d lived as this little red dwarf described a tiny arc of sky: marriage, two kids, a career, travel, retirement. I truly believe our lives are tied to the stars not in supernatural ways but in the meshing of cycles and as trackers of time. Stars are not only beautiful but they also offer opportunities for reflection.
You can see Barnard’s move, too. Use the maps provided to find it and then make a sketch showing its position in relation to other stars in the field of view. The larger your scope the more stars you’ll see and the more references you’ll have to track its movement. Knowing that Barnard’s Star is headed north, look for potential alignments where the star will form a straight line with two other field stars in the years ahead. Or you can do the opposite. Find a straight-line alignment now that will be broken as the star moves north. Two years from now return and observe the star again to see if it’s moved. Straight lines are easy for the eye to recognize; any deviation from a perfect line easily gives itself away.
I mentioned waiting 2 years.Large-scope owners will see movement in as little as a year. Yes, this is a long-time observing project but quite easy to do.You just have to remind yourself to return or the next thing you know 33 years will have gone by!
I hope you enjoy tagging along with Barnard’s Star. Besides the pleasure of watching a star move you can envision the distant future when no one currently alive would recognize the sky.