Mainers have last chance to spot the 'Christmas comet' in the sky this week
Dec. 21—PORTLAND, Maine — Bundle up, grab your binoculars or a telescope and head outside a bit after dusk this week for a Christmas present from the cosmos.
Comet Leonard, discovered just this year, is currently whizzing through our solar system. While it's no Star of Bethlehem beaming down over a stable, it's still worth finding in the night sky. Leonard is the final and brightest comet of 2021 — and it won't be back this way for another 80,000 years.
Dubbed the "Christmas comet" by many online night sky-watchers because of its late December visit, Leonard is not shining nearly as bright as comet NEOWISE did in the summer of 2020. Through binoculars or a small telescope, Leonard will look like a green smudge with a hint of a tail.
In its monthly "What's Up" online observation guide, NASA said comets are notoriously difficult to predict in terms of brightness and visibility.
"Comet Leonard is predicted to peak at a brightness that will probably require binoculars to spot it," it stated. "There's a chance it could be bright enough to see with the unaided eye, but again, with comets, you really never know."
A comet's brightness depends on how much sun-reflecting ice and gas it gives off at any given time.
Though it may not be visible with the naked eye, Leonard won't be hard to find and you won't have to get up in the middle of the night to see it. For the next week, it will appear right next to Venus, the brightest thing in the night sky other than the moon, about 45 minutes after sunset, just above the southwestern horizon.
Venus is so bright that it's usually the first night sky object you can detect at dusk. Keep your eye on that planet and you'll know where to look for comet Leonard as it gets darker. The comet will be a few degrees to the south, or left, of Venus.
While you're out there looking, you might also notice Saturn and Jupiter in nearly a straight line above Venus.
To help you catch a glimpse, you'll need to give your eyes time to adjust to the darkness. Don't look at your phone, or use a flashlight without a heavy, red filter. Stay away from streetlights or other artificial illumination.
Comet Leonard, officially called C/2021 A1, was discovered by its namesake astronomer G. J. Leonard on Jan. 3 at the Mount Lemmon Observatory in Arizona. It was actually closest to Earth on Dec. 12, passing within 21 million miles.
This week, it's closer to Venus, passing just 31,000 miles from that planet.
Leonard, like all comets, is a frozen leftover from the formation of our solar system. It's composed of dust, rock, and ice. Comets range from a few miles to tens-of-miles-wide, but as they orbit closer to the Sun, they heat up and spew gases and dust.
That's what makes their tails, which can be millions of miles long.
At the moment, Leonard is about a half-mile wide.
According to NASA, there are 3,743 known comets.
As you gaze at the southwestern night sky, keep one eye a little further west, in the constellation Gemini. It's unlikely, but possible you could catch a stray glimpse of light streaking out of the annual Geminid Meteor shower.
The shower, remnants of the asteroid Phaetheon, peaked last week.
"Whether you catch a glimpse of comet Leonard, or meteors from asteroid Phaethon," NASA wrote, "both are reminders of the deep connections between Earth and the rest of the solar system that we discover because we look outward, and we explore."
