Skywatchers still have time to spot 2021's most impressive cometary fly-by Comet Leonard, as it makes its way towards the sun. They will have to act quickly, however, as after passing the sun on January 3, 2022, the comet could be heading out of the solar system forever.
The comet, also known as C/2021 A1, will be closest to our star on January 3, 2022, at which point it will move out of view for observers here on earth.
Comet Leonard, the brightest comet of 2021 according to EarthSky, has been visible with binoculars and telescopes throughout December. The comet made its closest approach to Earth on December 12, passing to within 21 million miles of our planet.
But amateur astronomers were given another good opportunity to spot the comet following this, when it made an exceptionally close passage to Venus on December 17 and 18.
Because Venus, Earth's closest neighbor, is the brightest planet in the night sky, Leonard's proximity to the second planet from the sun gave astronomers an excellent reference point to spot the comet.
Anyone wanting to spot Comet Leonard, named after Greg Leonard, a senior researcher at the University of Arizona and the astronomer who discovered it in January 2021, should view it from a spot with dark skies. The comet is currently located in the constellation of Sagittarius.
"I feel there is going to be something to be seen even for the casual observer," Leonard said in a University of Arizona press release. "Find yourself a dark sky with a good view of the horizon, bring binoculars and I think you may be rewarded."
Comets tend to brighten as they approach the sun because the heat of our star causes material at the surface to turn to vapor. Comet Leonard seems to be brightening before even reaching its closest approach of 57.2 million miles from our star.
Despite this brightening, it is still best viewed with a telescope or a pair of binoculars. NASA says that as of December 12 the comet was just barely visible with the naked eye.
In addition to this steady brightening, the comet could undergo a series of outbursts of brightness as it gets closer and closer to our star.
Comet Leonard has come a long way to move into view from Earth. Space.Com reported that approximately 35,000 years ago the highly elliptical orbit of Comet Leonard saw it at over 330 billion miles from the sun.
This will very probably be Comet Leonard's last visit to the sun, its discoverer said. "This is the last time we are going to see the comet," Leonard said. "It's speeding along at escape velocity, 44 miles per second. After its slingshot around the sun, it will be ejected from our solar system, and it may stumble into another star system millions of years from now."
Comets like Leonard provide astronomers with a great way of studying the solar system's formation. This is because they are comprised of material present in the earliest epoch of our planetary system.
This is especially true when they have spent all their time at the freezing outskirts of the solar system like Leonard has, unspoiled by the radiation of the sun.
"As much as we have great science on comets, they're still highly unpredictable with respect to their size, shape, chemical makeup, and behavior," Leonard said. "A wise and famous comet discoverer once said: 'Comets are like cats—both have tails and both do precisely what they want.'
Correction 12/22/21 at 6:19 a.m. ET: This article has been updated to correct how closely Comet Leonard will pass Earth.
