A spectacular new cosmic spectacle could erupt in the night sky over the Bay Area on Memorial Day — but again, that may not be the case.
Astronomers are on edge over the Tau Herculids, an unprecedented meteor shower that could possibly appear around 10 p.m. on May 30. Made up of fragmented particles from Comet Schwassmann-Wachmann 3, which began to disintegrate in 1995, the debris is expected to intersect Earth’s orbit again next week – but this time it may be visible to the eye. naked.
NASA models show that if the particles were ejected at a high enough speed when it dissolved, North America could see the meteor shower.
But if the particles were slow-moving, don’t expect to see much more than the usual constellations and maybe an orbiting satellite that night.
“It could be a meteor storm, which is spectacular,” said Robert Lunsford, fireball report coordinator for the American Meteor Society. “But it could be so dark that no one sees it except radar.”
For there to be a meteor storm, debris from the comet had to be ejected at nearly 60 miles per hour, which would result in “a prolific display of very slow-moving, bright, and colorful meteors,” according to a Journal article by Joe Rao, a professor of astronomy at the American Museum of Natural History.
However, debris from the comet is moving in the same general direction as Earth, meaning any meteor would move much slower than expected for a meteor shower, according to the American Meteor Society. While this doesn’t entirely prevent a fireball storm from occurring, it does make it more unlikely.
A faint comet Schwassmann-Wachmann 3 was first observed in 1930, returning approximately every 5.4 years thereafter. When the still-intact comet appeared in the night sky in 1995, it was much brighter, visible to the naked eye and sporting a tail of dust, according to Harvard’s Astronomical Telegram Central Bureau.
Astronomers observed that the comet broke into several large pieces as it approached the sun in 1995, and these pieces have since disintegrated further.
Larger fragments from the burst of comet Schwassmann-Wachmann 3 are expected to lie ahead of the comet’s path for North America to see a meteor shower.
A large flux of material was left behind by the comet’s burst, with potentially 100 slow-moving meteors per hour, said Gerald McKeegan, assistant astronomer at the Chabot Space and Science Center in Oakland.
Although astronomers have predicted the appearance of a meteor shower several times since the comet broke up in 1995, the May 30 forecast is more promising than previous forecasts.
“This year, the cluster of particles left behind by the 1995 orbit is heading toward that same region of space,” McKeegan said. “The comet’s orbit is parallel to Earth and passes through the plane of Earth’s orbit.”
The Tau Herculids were named because a possible meteor shower would appear to originate from the star Tau, located in the constellation of Hercules.
But the comet’s radiant has changed since it was first calculated in 1930, appearing all over the sky, Lunsford said. It will actually appear to come from the constellation Boötes, which is close to the bright star Arcturus.
Bay Area viewers who want to catch a glimpse of the possible downpour will be in luck: the Tau Herculids fall on a new moon. Without moonlight to wash out objects in the sky, it is easier for the naked eye to see fainter phenomena.
But if the meteors appear, people in urban areas are unlikely to see them due to the glow of the San Francisco skyline and the lights of the surrounding suburbs.
For the chance to see the whole show, go somewhere with little light pollution, preferably an hour before, around 9 p.m., to allow your eyes to adjust to the darkness. Bring binoculars for a closer look.
According to EarthSky, several calculations place the peak of the shower between 9:55 p.m. and 10:17 p.m. on the West Coast. Although experts don’t know how long the meteor shower will last, preparing to see the rain early can help if peak hour estimates are off.
But don’t get your hopes up, even with promising models, the astronomers said.
“This one looks favorable, but there’s a lot that has to happen for the general public to come out and be enamored with this,” Lunsford said.
If the Tau Herculids don’t deliver, the next big meteor shower visible in the Bay Area will be the Perseids, which begin in July and peak on August 13.
Gwendolyn Wu (her) is a staff writer for the San Francisco Chronicle. Email: gwendolyn.wu@sfchronicle.com