Sunspots are dark areas on the solar surface that contain transient and concentrated magnetic fields. They are the most prominent visible features on the photosphere Sun; a moderate-sized sunspot is about as large as Earth. Sunspots form and dissipate over periods of days or weeks. They occur when strong magnetic fields emerge through the solar surface and allow the area to cool slightly, from a background value of 6000 degrees C down to about 4200 degrees C; …showed first 75 words of 603 total…

…showed last 75 words of 603 total…high-energy particles into living cells, measured as radiation dose, leads to chromosome damage and, potentially, cancer. Large doses can be fatal immediately. In October 1989, the Sun produced enough energetic particles that an astronaut on the Moon, wearing only a space suit and caught out in the brunt of the storm, would probably have died. (Astronauts who had time to gain safety in a shelter beneath moon soil would have absorbed only slight amounts of radiation.)