The Largest Sunspot Group in Nine Years

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Movies of meridian crossing: MPEG (large, small), QuickTime (large, small). Movies of entire disk transit: MPEG (large, small).
High-resolution movies: MPEG (large, small), QuickTime (large, small).

Caption: Active region 9169 was the host of the largest sunspot group observed so far during the current solar cycle. On 20 September 2000, the sunspot area within the group spanned 2,140 millionths of the visible solar surface, an area a dozen times larger than the entire surface of the Earth!

Caused by intense magnetic fields emerging from the interior, a sunspot appears to be dark only when contrasted against the rest of the solar surface, because it is slightly cooler than the unmarked regions.

The sunspot rotated across the disk of the Sun towards the right (which in fact means towards west, as seen from the Earth), as it gradually changed appearance (MPEGs: large, small).

You can look for sunspots any time, day or night, on the web: The image below shows the latest white light image from MDI. You can also follow the development of sunspots and other solar activity from our real-time images page.

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Related stories:

• Space.com
• BBC News
• History's biggest sunspots from SpaceWeather.com
• How to watch sunspots from SpaceWeather.com (Careful!)
• SpaceWeather.com

Picture Credit: SOHO/MDI (ESA & NASA)
Special thanks to: Rock Bush, Julia Saba, Phil Scherrer, Keh-Cheng Chu.
Instrument/observatories: MDI (Michelson Doppler Imager);
Taken: 22 September 2000, 09:36 UT