Why Wednesday night could offer Bay Area skywatchers a spectacle

One of the best meteor showers of the year peaks Wednesday night into Thursday morning, and Bay Area skywatchers who find a break in the clouds may be able to catch a glimpse of the cosmic spectacle. The Geminids meteor shower can produce up to 120 meteors per hour, according to NASA.

Sarah McCorkle, a forecaster with the National Weather Service, said partly cloudy conditions are expected overnight, with high clouds moving into the region Wednesday afternoon and sticking around into Thursday. 

“You may find some areas where the cloud cover is sparse,” McCorkle said. 

The clouds will be high in the atmosphere, so even if you went to a location that’s high in elevation, such as Mount Tamalpais in Marin, you could run into clouds, she added. 

The Geminids meteor shower occurs annually in mid-December as Earth passes through the dusty cloud trailing a 3-mile-wide space rock.

“The Geminid meteors are a stream of particle left behind by the near-Earth ‘asteroid’ 3200 Phaethon,” Gerald McKeegan, adjunct astronomer at Oakland’s Chabot Space & Science Center, told SFGATE via email. “This asteroid is actually an old, dead comet that orbits the Sun every 17 months. Phaethon has been around millions of years, but it was not discovered until 1982.”

The meteor shower gets it name from the Gemini constellation that will be high in the eastern sky on Wednesday.

“As Earth orbits the Sun, its direction of motion in mid-December is toward the constellation Gemini,” McKeegan said. “That gives the illusion that the meteors come out of Gemini, when it is actually the Earth that is plowing into the particle stream from the comet. But the meteors can appear in any part of the sky, so it is important to watch the whole sky rather than just looking toward Gemini.”

While the meteor shower activity started on Nov. 19 this year and is expected to continue through Dec. 24, the peak is expected the night of Wednesday, Dec. 13, and the early morning of Thursday, Dec. 14. On Wednesday, it will be possible to see meteors as early as 9 p.m., and the meteor shower will strengthen into the evening, reaching its height between 11 p.m. Wednesday and 3:30 a.m. Thursday, McKeegan said.

Meteor showers are best viewed outside city areas away from urban light pollution with the naked eye. 

“The meteor shower will be active all night long, although the waning gibbous moon may make it difficult to see the fainter meteors,” McKeegan said.