Last week's solar eclipse tripled by Hinode

Bad Astronomy
The entire universe in blog form
Dec. 5 2011 7:00 AM

Last week's solar eclipse tripled by Hinode

Did you know there was a solar eclipse last week? Probably not, since -- due to the geometry of the Moon's orbit around the Earth -- it occurred over Antarctica.

However, it was seen by the Japanese Sun-observing satellite Hinode (pronounced, "HEE-no-day"; meaning "sunrise"). As the satellite moved around the Earth, its viewing angle of the Moon changed, so it saw the eclipse not just once but three times, making for a very odd video of the event:

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  


This change in perspective is called parallax, and besides tripling the eclipse fun, it also manifests itself as a severe curve to the Moon's motion in the video. If the satellite were hovering over the Earth, it would've seen just one eclipse as the Moon slowly moved across the Sun's face (if it had been over Antarctica at the time). But the satellite orbits the Earth at a height of about 700 km (400 miles), moving at several kilometers per second. That motion is reflected in the apparent path of the Moon in the sky, and so it saw not just one but three eclipses. Something like this happened earlier in the year with another solar satellite, and I have a more a more detailed explanation in a post about that event.

One of the biggest positive aspects of being a space-faring race is the change in perspective we get by seeing things from a different angle... and in this case, it's literally a continuously changing perspective. It's a great reminder that the way we perceive the Universe from the Earth's surface is not the only way to do so, nor necessarily the best way.

Credit: Credit: Smithsonian Astrophysical Observatory

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