By Scott Levine
Though we often think of the sky as permanent and unchanging, one of the greatest pleasures of watching often is seeing it change from night to night.
With enough time, we get to see stories unfold little by little. From one night to the next, we see the moon jump across the sky, darting from place to place as its sunlit part grows and shrinks and its phases change. If we look closely enough, we can even see the moon creep slowly and silently across the sky during the course of a night, sneaking up on the stars around it.
These changes happen with our view of the stars, too. Their positions, relative to each other, stay the same, but they rise four minutes earlier each day. This means they’re a little farther to the west at the same time tonight than they were last night, a little closer to setting.
As we keep going with our quarantine star party, let’s find the Big Dipper high toward the northwest after dark. If we draw a line between the two stars at the far end of its bowl and continue it toward the west (to the left), we’ll get to the constellation Leo.
This patch of sky has represented a lion in the mythology of cultures going back to the ancient Persians and Sumerians, while Chinese myth sees it as a horse. Among the modern constellations, it’s one of the few that kind of looks like what it’s supposed to be.
Our line from the Big Dipper brings us to Leo’s rectangular midsection. Toward the ground, let’s see if we can make out the backward question mark-shaped group called the “Sickle,” which makes up its front end. The dot at the bottom is the bright star Regulus, which is actually four stars about 80 light years away, orbiting each other in two pairs. Once we’ve found that, look higher up for the triangle that makes up its hind quarters. The star at its tail is called Denebola.
A few months ago, when spring was still on its way, the lion returned to our chilly nights, rising with the Sickle rearing over the eastern sky. In the weeks since, we’ve collected those four minutes each night as it crossed high overhead. Now, with only a few weeks left until summer, Leo starts the night in the west, lurching toward the horizon and about to pounce on something just below. As our view of the sky goes, that happens to be the unsuspecting and unfortunate heads of Castor and Pollux, the twins of Gemini or Cancer, the crab.
If we keep an eye on this patch of sky from May 28 to May 30, we’ll see a waxing crescent moon hop like a speedy rabbit past the lion, growing as the nights pass. It’ll be full on June 5.
As the seasons change, the skies do, too. Before long Leo will vanish into another impossibly long summer sunset. The bright summertime star Vega has already come back to the northeast. Soon, Aquila the eagle, Cygnus, the swan, Scorpius the scorpion and the rest of summer’s stars will join the fun, tell their stories and cross the sky – four minutes at a time. I hope you’ll take a look.
Scott Levine (firstname.lastname@example.org) is an astronomy writer and speaker from Croton-on-Hudson. He is also a member of the Westchester Amateur Astronomers, which is dedicated to astronomy outreach in our area. For information about the club, including membership, newsletters, upcoming meetings and lectures at Pace University and star parties at Ward Pound Ridge Reservation, visit westchesterastronomers.org. Events are free and open to the public. Please note: All in-person club activities are suspended until further notice due to COVID-19.