Astronomy Picture of the Day

Explanation: The Sun's surface keeps changing. Click the central arrow and watch how the Sun's surface oozes during a single hour. The Sun's photosphere has thousands of bumps called granules and usually a few dark depressions called sunspots. The above time-lapse movie centred on Sunspot 875 was taken last year by the Vacuum Tower Telescope in the Canary Islands of Spain using adaptive optics to resolve details below 500 kilometres across. Each of the numerous granules is the size of an Earth continent, but much shorter lived. A granule slowly changes its shape over an hour, and can even completely disappear. Hot hydrogen gas rises in the bright centre of a granule, and falls back into the Sun along a dark granule edge. The above movie and similar movies allow solar scientists to study how granules and sunspots evolve as well as how magnetic sunspot regions produce powerful solar flares.