June 15, 1999
The Earth has carried you around the Sun again, steady as ever, while the stars kept their patient watch.
The Sun Oscillates
Birthday · June 15, 1999
A little universe, just for you
Your date.
Ready to give.
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APOD published June 15, 1999. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
Our Sun is in a continual state of oscillation. Large patches of the Sun vibrate in and out, back and forth, even as the Sun rotates. One mode of Solar oscillation is depicted graphically above, with blue indicating outward motion, and red indicating inward motion. Although sensitive optical solar observatories can only directly detect surface motions, they give information about vibrations occurring much deeper in the Sun. In helioseismology, these oscillations are being analyzed and are revealing unprecedented information about the density, temperature, motion, and chemical composition of the entire Sun.