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SYFY WIRE Bad Astronomy

When the Earth photobombs the Sun

By Phil Plait

The Solar Dynamics Observatory is a NASA satellite that observes the Sun 24 hours a day. It orbits the Earth, placed carefully so that it takes 24 hours to circle the Earth once -- what we call a geosynchronous orbit. This maximizes its output, and allows scientists to squeeze as much data from it as possible.

But, twice a year, the geometry of SDO's orbit aligns in such a way that the Earth itself gets between the observatory and the Sun. When that happens, you get an eclipse! We're in one of those "eclipse seasons" now, and around midnight last night UTC one such eclipse occurred. The folks at SDO created a nifty video from the images collected during that time:

That's cool. You can see the Earth barreling through the image, blocking SDO's view. SDO has several different cameras which look at the Sun at different wavelengths of ultraviolet and optical light. The first view, colored red, is actually in ultraviolet (at 304 Angstroms, if you're keeping track). The next view, colored gold, is even further in the UV (193 Angstroms). Then they cycle through a bunch of different wavelengths, giving a psychedelic journey through an eclipse that reminds me of the ferry ride from "Willy Wonka".

"There's no earthly way of knowing, which direction we are going..."

I've written about all this before; see Related Posts below for more.

And I'll leave you with this question: when the Moon passes between the Earth and the Sun, it's a solar eclipse, and when the Earth passes between the Sun and the Moon, it's a lunar eclipse. So what do we call it when, for us on the surface, the Earth gets in between us and the Sun?

Answer: night.

Tip o' the dew shield to Camilla Corona SDO on Google+.

Related Posts:

- When the Earth takes a bite out of the Sun
- Moon bites multicolor Sun⦠from space!
- An eclipse from space with a two-way Moon
- SDO lunar transit: now with video!
- Solar eclipse, from space!

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