Quietly, like an unassuming guest entering through the back door of the Geminid meteors’ holiday party, we now have greenish company in our skies. Say hello to Comet 46P/Wirtanen.
Wirtanen just made its closest approach to the sun and, from 7.2 million miles away, will dart past Earth on Dec. 16. In the days ahead it may — emphasis on the word “may” — increase enough in brightness to unveil itself to the naked eye.
If the comet brightens to a third-magnitude object, the human eye could technically see this fuzzy, blue-green cotton ball (assuming perfectly dark conditions, with eyes adapted to dark conditions, far away from light pollution). But a pair of binoculars is your best bet. Aim your eyes toward the Pleiades (or Seven Sisters) star cluster to find the comet.
Wirtanen will be in the eastern sky during the early evening, and the comet will be due south near 10 p.m., said Geoff Chester of the U.S. Naval Observatory. Find it in the western sky, still near the Pleiades at about 2 a.m.
Comet Wirtanen orbits the sun every 5.44 years, and it is part of a comet family shaped by the planet Jupiter’s gravity, according to Chester.
Earth has been visited by Wirtanen many times. On the comet’s last visit, in 2013, viewing conditions were generally poor. For its next tour in 2024, the viewing probabilities are also expected to be poor, according to the University of Maryland’s Comet Wirtanen Web pages.
The 2018-type close approach will not happen again for at least 20 years, Chester noted.
The Maryland astronomers report the comet reached fifth magnitude earlier this week, as predicted, but cruising around the sun, the comet should brighten.
While the comet is close to the Earth, it will not come all that close in Earthly terms. The streaking dirty snowball is about 30 times the distance from Earth to the moon, according to NASA.
This comet was discovered in January 1948 at the Lick Observatory on California’s Mount Hamilton, and it is among five discovered by astronomer Carl Wirtanen. Majoring in physics, mathematics and astronomy, Wirtanen earned his bachelor’s degrees (1936) and his master’s degree (1939) from the University of Virginia. He was born in 1910 in Kenosha, Wis.
At age 12, Wirtanen’s violin teacher brought him to a local observatory so he could see the cosmos through a telescope, according to the American Astronomical Society’s obituary. The observatory visit led him to make his own reflecting telescope, the obituary said, “deepening his interest in astronomy.”
We can today use his namesake comet to deepen our own interest in the skies above.