ANOTHER insanely awesome shot of the solar eclipse?!

Bad Astronomy
The entire universe in blog form
Jan. 8 2011 7:00 AM

ANOTHER insanely awesome shot of the solar eclipse?!

Y'know, I should never deal in superlatives. I said Thierry Legault's shot of the ISS during the solar eclipse last week was the best picture of it, but now, as amazing as that picture is, I think we've found something to tie it: the Japanese solar observing satellite Hinode took this jaw-dropping video:


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!  

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OK, I'll say it: Holy Haleakala!

Hinode (pronounced HEEN-oh-day, which I'm telling you because I always say HI-node in my head when I see it) orbits the Earth, and has a near-continuous view of the Sun. When the Moon slipped between us and our star on January 4, Hinode had what might have been the best view. This video was made using images from the X-Ray Telescope, or XRT, and is sensitive to objects at temperatures of millions of degrees -- the Sun's magnetic field routinely generates such energies. You can see the looping material on the Sun, following the arcing lines of magnetism. The Moon is dark at these wavelengths, so it appears black in the video.

The other cool thing is the size difference between the Sun and the Moon. The Sun is roughly 400x bigger than the Moon and 400x farther away, so they look about the same size in the sky. But the Moon orbits the Earth in an ellipse, and can change its distance to us by quite a bit, well over 10% -- that means its apparent diameter as seen on Earth can change by 10% too.

During the eclipse, the Moon was roughly 391,000 km away from Hinode, a good 6000 km more than average, making the Moon appear somewhat smaller than average. Not only that, but the Earth orbits the Sun in an ellipse as well, and it so happens this eclipse happened within hours of perihelion, when the Earth was closest to the Sun. That difference is only about 3%, but still, every little bit helps! The Sun was about as big as it can be at the same time the Moon was smaller than usual, so the Moon couldn't completely cover the Sun.

And you can see that in this video! Even when the Moon is solidly in front of the Sun, you can still see a ring of Sun around the Moon. This type of eclipse is called an annular eclipse (annulus mean ring)*.

And here's your thought for the day: right now, the Moon recedes from the Earth at a rate of about 4 cm a year due to tides (y'know, those things Bill O'Reilly doesn't understand). Over time it'll move so far away that even with its elliptical orbit it'll always be smaller than the Sun, and every solar eclipse will be annular. So you'd better watch these eclipses while you can. In a billion years or so there won't be any more total ones.

Tip o' the welder's goggles to Alexrkr7. Image credit: Hinode/XRT



* Too bad the Sun was in Sagittarius at the time, and not Taurus. HAHAHAHA! Get it? Taurus? Like torus? No? OK, go back to the main text.


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