You might be a newbie at spotting astronomical phenomena, but that doesn’t mean you have to sound like one. Here are six words that will help you show off your eclipse smarts.
Syzygy: That’s right, it takes three Ys to describe three astronomical objects lining up. In the case of a solar eclipse, that’s the sun, the moon and Earth in that order. But syzygies are actually pretty common. In fact, we experience one every two weeks or so: All new and full moons qualify — a total solar eclipse is just a particularly special new moon.
Umbra and penumbra: The umbra is the darkest part of the shadow the moon casts during an eclipse, while the penumbra is the lighter shadow. On the ground, these two regions translate into where someone sees a total solar eclipse (in the umbra) and where someone sees a partial solar eclipse (in the penumbra).
Saros cycle: The Saros cycle describes the strange tendency eclipses have to repeat themselves. For centuries-long spurts, every 18 years and change, the sun, moon and Earth line up with the moon about the same distance from Earth. This doesn’t mean the same place will see an eclipse every 18 years — because of how the moon and Earth rotate, every fourth eclipse in a Saros cycle will retrace a similar piece of ground. There are about 50 different Saros cycles running at any given time, but the eclipse this year is part of Saros 145.
Corona: During totality, all you’ll be able to see of the sun is its outermost layer, the corona, which is too faint to see when the rest of the sun’s light isn’t blocked. It’s also the hottest part of the sun, thanks to the star’s magnetic fields.
Baily’s beads: Just before and after the brief period of totality, flashes of sunlight generally shine out along the edge of the moon that’s encroaching over the sun (or retreating after the end of totality). That’s because the moon’s surface is riddled with mountains, craters, canyons and other features with height and depth. Where the lunar landscape cuts into the moon, small amounts of light can shine past the darkness.
Cookie bite: Okay, so this isn’t a big fancy term, but we aren’t making this up — this is really what so-called eclipse chasers call the beginning of a partial solar eclipse, when the moon takes a bite out of the sun.
What you need to know about this summer’s total solar eclipse — the first to hit North America in nearly a century. Find out how to use NASA’s interactive map, the best places to go to see the rare event and learn the physics behind the eclipse.