Comet C/2021 A1 (Leonard) – 2021’s best and brightest comet – is now in the evening sky for Northern Hemisphere observers. We heard on December 15, and again around December 19-20, that the comet had brightened more than expected. Is it having outbursts as it nears its closest point to the sun in January?
New reports on December 20 also indicate its tail is slightly bigger. So keep watching the comet this week!
As always, dark skies are recommended for this diffuse object. And – although we’re not hearing reports of people viewing the comet with the unaided eye – Comet Leonard is still a good binocular comet. And it’s near Venus, the brightest planet! Comet Leonard swept closest to Earth on December 12, 2021, passing some 21 million miles (34 million km) away. Its exceptionally close pass of bright Venus (2.6 million miles, or 4.2 million km) happened on December 17-18.
Closest approach to Venus was at 9:08 p.m. ET on December 17 (02:08 UTC on December 18).
Comet Leonard will round the sun at perihelion on January 3, 2022, at a distance of about 56 million miles (0.6 AU, or 90 million km). Comets are typically brightest around perihelion, and the comet has been brightening and is still getting brighter. And, as recent activity shows, there’s always the possibility of brightness outbursts as Comet Leonard draws nearer and nearer the sun.
By the way, astronomer Greg Leonard discovered this comet as 2021 began, giving it its name. It’s been much-anticipated, and it’s turning out to be quite a fine object for viewing!
So Comet Leonard is the best comet we’ve had this year. Ordinary 7×35 or 10×50 binoculars from a discount store will surely show it to you (if your sky is dark). The comet might be glimpsed with the eye alone, the tricky thing will be to catch it at just the right time after sunset, not too early (when bright twilight will wash it out) and not too late (when it will have set). The free, online planetarium program Stellarium can provide a view from your location.
Nature provides us with sky events seen once in a lifetime, Comet Leonard is one of these. By that we mean that this comet takes tens of thousands of years to complete an orbit around the sun. As Bob King pointed out at Skyandtelescope.com in October 2021:
Orbital calculations revealed that the object had spent the last 35,000 years wending its way sunward after reaching aphelion at the chilling distance of around 3,500 AU (3,500 times the distance between our Earth and sun).
An amazing feature of this celestial visitor is that it’s an ultrafast comet. It’s traveling at 158,084 miles per hour (254,412 km/h or 70.67 km/second) relative to Earth.
But, despite its incredible speed through the vast space of our solar system, don’t expect to see this comet swoosh across the sky. Like planets, comets do move in front of the star background. But, to our eyes, they appear to move slowly due to the large distances involved. Is it possible to observe this comet’s motion.
Yes, if you’re a careful observer and willing to spend some time. The best way would be with a small telescope. You’d do it by taking a close look at the comet’s position relative to background stars. Then compare the telescopic view five or 10 minutes later to detect the comet’s motion. Despite its high speed, you’ll find that its distance from Earth – and the vast distances in our solar system – will cause the comet to appear as a very slow-moving object.
Comet C/2021 A1 (Leonard) on December 21, 2021 from Rincon, Puerto Rico by Raymond Negron. (92mm Refractor Telescope)
Comet Leonard photos in the morning sky
Bottom line: Comet Leonard (C/2021 A1) – discovered on January 3, 2021 – is heading inward toward its January 3, 2022, perihelion. It still might become the brightest comet of 2021! Photos and charts here. Bookmark this post. We’ll be updating it.
Eddie Irizarry of the Sociedad de Astronomía del Caribe (Astronomical Society of the Caribbean) has been a NASA Solar System Ambassador since 2004. He loves public outreach and has published multiple astronomy articles for EarthSky, as well as for newspapers in Puerto Rico. He has also offered dozens of conferences related to asteroids and comets at the Arecibo Observatory.
Asteroid 33012EddieIrizarry, a 7.8 km space rock, has been named in his honor.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.
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