Hey, everyone. Don’t you hate the weekends when you look back and have nothing to show for those couple of days? I threw something together for this other, non-astronomy writing project I’m working on, and it makes no sense. Funny, I don’t remember writing it at 3 A.M. after an extra beer. Always be writing, though, has been the mantra lately, with an image of Alec Baldwin’s character in Glengarry Glen Ross in my head. Sure as the Moon circles, with 5.5% eccentricity, the earth, even when the word don’t come, the words will come. It’s good to be in the right place when they do.
Anyhow, the sun is up, at the moment the sky is clear, the coffee is hot and the guinea pigs are squealing. Things move along. Later this week, we’ll be in for an eclipse of the moon. That’s the first eclipse of the new year (can you still say “the new year” in February?), so how about today we run down the eclipses we have ahead of in 2017?
An eclipse happens when two objects line up so that they cast a shadow on a third. They can happen anywhere you have a light source, an opaque thing, and something to wander into the shadow. So, the Sun and Europa can eclipse Jupiter. A bright spotlight and a tree can eclipse someone walking past them on a summer night. For our purposes, we’ll talk about two main types of eclipses:
- Solar eclipse, which is when the moon gets between the sun and Earth, and part of Earth falls into the moon’s shadow. Since the moon needs to be directly between the sun and Earth, solar eclipses can only happen when the moon is new. The line is arranged Sun-Moon-Earth.
- Lunar eclipse, when the Earth is between the sun and the Moon (the line is Sun-Earth-Moon), and the moon falls into Earth’s shadow. Since the moon needs to be directly opposite the sun from the earth, lunar eclipses can only happen when the moon is full.
Eclipses don’t happen every month, though, because the moon’s orbit is inclined by about 5 degrees relative to Earth’s orbit. So, the moon needs to be either full or new exactly when it crosses the orbital plane in order for it to pass directly in front of the sun from our point of view, or directly into Earth’s shadow.
This year, we’ll have four eclipses:
- Penumbral Lunar Eclipse: February 10. All shadows have a deep, dark portion, called the umbra, and the hazier outer part, called the penumbra. On the evening of the 10th, the moon will slide through that outer penumbra. If you’re in North or South America, you’ll be able to see some shadowing, but it won’t be that deep, alluring red that we saw a couple of summers ago (I promised myself I wouldn’t say “blood moon”). In the northeast US, you’re in luck, the moon will be entering the shadow just as it rises, and will hit mid-eclipse at 7:45.
- Annular Solar Eclipse, February 27: The root of the similar-looking word “annual,” is the same as “annular,” ring-shaped. When there’s a solar eclipse far enough after perigee, the time when the moon is at the nearest point in its orbit around Earth, its face isn’t big enough to cover the whole face of the sun, as seen from here. So, when the moon crosses the sun, it leaves an uncovered part, a ring of fire. This annular eclipse will be pretty close to total, but not. Unfortunately, most of this one happens over open ocean, so not a lot of people will see it. The maximum of the moon’s shadow will make landfall in southern South America and Africa.
- Partial Lunar Eclipse, August 7: This time around, part of the full moon will dip into that dark, central part of the earth’s shadow and turn that deep red color. It’ll be able to be seen in Africa, Asia, Australia, and eastern Europe.
- Total Solar Eclipse, August 21: This is the big one here in the US. For the first time since 1979, a total solar eclipse will be visible in the lower 48 US states (a total eclipse was visible in Hawaii in 1991). This time, the moon will eclipse the sun when the moon is very close to perigee, which is just three days earlier. Unlike in February, this time, it’ll be able to cover the entire face of the sun. The moon’s shadow will be visible coast-to-coast across a narrow path running from Oregon to South Carolina. Lots of people are very excited about this one, and maybe the last few of us who haven’t yet can find someplace to camp so we can see it.
We’ll talk more about these as they get closer, but for now, maybe write these on your calendar and get ready to enjoy the show. Thanks for stopping by, and clear skies, everyone!