Astronomically speaking, it's shaping up to be a busy weekend, with a “supermoon” on Saturday and the vernal equinox on Sunday, heralding the arrival of spring.
The moon is closest to Earth due to the gravitational pull of the sun once every 18 years, and on Saturday during this time the full moon will be bigger and brighter than usual.
“It's called a supermoon, and it's a few percent larger than a normal full moon,” said George Royer, director of the Valley of the Moon Observatory Association's Robert Ferguson Observatory. “It's interesting, but we won't know until we measure it. It's not going to look that big.”
Forecasters say the weather may improve this weekend, but the full moon likely won't be visible through the storm clouds.
Technically, the moon is about 221,565 miles away at a point called perigee, compared to its apogee, which is 251,880 miles when it is farthest from Earth.
But not all perigees and apogees are the same: The moon is also affected by the sun's gravitational pull while in orbit, causing slight changes in its orbit about every 18.5 years, Royer said.
“Sky-watchers may notice a difference,” said Ed Megill, director of the Santa Rosa Junior College Planetarium, “but it won't be, so to speak, spectacular.”
The Moon, which is one-quarter the size of Earth, will also have its strongest influence on the oceans during this time, causing the highest tides.
Bodega Bay is expected to see a 6.2-foot storm surge at 12:29 a.m. Monday, a 6.3-foot storm surge at 1:08 a.m. Tuesday and a 6.2-foot storm surge at 1:52 a.m. Wednesday.
The vernal equinox, the day when day and night are of equal length, occurs on Sunday at 4:21 p.m. when the sun crosses the equator and enters the Northern Hemisphere.
“The sun is up longer, at a higher angle, and warmer weather is starting to set in,” Megill said. “It's been called the start of spring.”
