Flash forward to the week of Dec. 20, 2021, and a “Christmas comet” is streaking through the evening sky.
Comet Leonard, or C/2021 as it is officially known, is the brightest comet of 2021. The celestial object actually made its closest approach to Earth on Dec. 12, when it was about 21 million miles away from our planet.
However, stargazers can still catch this once-in-a-lifetime sighting this week as it passes through the solar system, according to Gregory Leonard, a senior research specialist at the University of Arizona’s Lunar and Planetary Laboratory. Leonard first discovered the comet earlier this year, and it’s named after him.
Originally visible in the dark skies before sunrise, Leonard can now be seen in the evening sky and is best viewed at twilight.
“Beginning Dec. 13, this comet will appear very low above the horizon just after sunset,” Leonard explained in a U of A news release. “It will skim across the west-southwestern horizon between now up until around Christmastime.”
And while the comet has since flown by Venus, reports indicate that the celestial object has been steadily brightening, making it potentially visible to the naked eye.
As Space.com notes, though, it may still be tricky to see Comet Leonard without the aid of a telescope or binoculars for two reasons: the comet’s current placement and the moon.
C/2021 is visible low and near the southwestern horizon, with the best viewing time around an hour or so after sunset. That means the comet is competing with the fading light of dusk as opposed to the pitch black background of a clear night sky — a less than ideal situation to spot the small, bright object.
The second viewing challenge is the moon, which remains nearly full, thus adding further illumination to the evening sky when it rises.
However, skygazers will likely get an assist from “evening star” Venus, which currently appears prominently in the southwestern sky at twilight and may make it easier to spot Comet Leonard, according to the University of Arizona.
“I feel there is going to be something to be seen even for the casual observer,” Leonard said. “Find yourself a dark sky with a good view of the horizon, bring binoculars and I think you may be rewarded.”
The comet will progressively dim as it heads toward and passes the sun, something that is expected to happen around Jan. 3, 2022.
Leonard last flew by Earth about 80,000 years ago, so if you miss the comet this time around, you won’t get another chance to glimpse it in your lifetime.
“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.”