Comet Leonard moves toward Earth

On December 12, 2021, Comet Leonard (C/2021 A1) will be only 35 million kilometers from Earth and can be seen with the naked eye in the morning sky. This is what it looked like last night.

Austrian astrophotographer Michael Jaeger took this picture Nov. 11 with an 11-inch telescope. The comet was shining as a 9th magnitude star in the northern constellation Canes Venatici (Hunting Dogs). A close look shows a narrow jet of gas emerging from the comet’s atmosphere. This is the “ion tail” of the comet.

Over the next month, the brightness of the comet will increase dramatically, perhaps more than 100 times. Most forecasters agree that Comet Leonard will reach a +4 magnitude, become an easy target for small telescopes, and be visible to the naked eye from areas of dark sky in the second week of December.

Above: The blue curve shows the predicted brightness of Comet Leonard. The crosses are recent observations.

As the comet approaches the Sun in early January, direct scattering of sunlight through the comet’s dusty atmosphere could create an additional brightness burst of up to +1 magnitude. The same phenomenon occurred with comet McNaught in 2007, making it visible in daylight.

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