Thursday, September 23, 2010

Happy Autumnal Equinox

Thanks to a trip to Astronomy Picture Of The Day, I was reminded that today is the fall equinox. Well, I suppose you could say it happened yesterday in North America, as it was at about 3AM Greenwich Time. Naturally enough, APOD celebrated with this picture of the Sun:
Caption: Today, the Sun crosses the celestial equator heading south at 03:09 Universal Time. Known as an equinox, this astronomical event marks the first day of autumn in the northern hemisphere and spring in the south. Equinox means equal night. With the Sun on the celestial equator, Earth dwellers will experience nearly 12 hours of daylight and 12 hours of darkness. Of course, in the north the days continue to grow shorter, the Sun marching lower in the sky as winter approaches. To celebrate the equinox, consider this view of the Sun in extreme ultraviolet light from the Sun staring Solar Dynamics Observatory. Recorded yesterday, the false-color image shows emission from highly ionized iron atoms. Loops and arcs trace the glowing plasma suspended in magnetic fields above solar active regions.

Image credit: NASA / Goddard / SDO AIA Team

Clicking on the image credit link will take you to the original page, which has links to further explanations, and a link to the full sized image. Clicking on the image in this article will take you to the medium-sized version of the image I downloaded.

Happy Equinox.

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