QUIET SUN: Except for some minor rumblings on the sun's northeastern limb, solar activity is very low. The sun's X-ray output has nearly flatlined and NOAA forcasters put the odds of a major flare today at less than 10%.

FAST-MOVING SUNSPOT: Today in the blue skies above Scarborough Marsh, Maine, a dark-winged shape flitted across the face of the sun. It was the International Space Station:

"The ISS cut across the sun, transiting the entire solar disk in only 7/10th of a second," says amateur astronomer John Stetson who photographed the passage with split-second timing. "In today's transit the ISS appeared to be 54 arc seconds in angular diameter." In other words, it subtended an angle about the same as the planet Jupiter. Because the ISS is so large, it is possible to see the details of its structure through backyard telescopes. Here's a telescope that works both during the day and at night.

RADIATION BELT STORM PROBES--DELAYED: The approach of Tropical Storm Isaac has prompted NASA to push the launch date of the Radiation Belt Storm Probes all the way back to Aug. 30th. This will give Isaac time to pass, so the probes can lift off into better weather. Once they leave Earth, the twin probes will undertake a 2-year mission to study the Van Allen Belts and unravel the mystery of their dangerous unpredictability. [Launch Blog]

NEIL ARMSTRONG (1930-2012): Former U.S. astronaut, Neil Armstrong, the first man on the moon, died yesterday at the age of 82. "Neil was among the greatest of American heroes - not just of his time, but of all time," said President Obama in a statement on Armstrong's passing. "Today, Neil's spirit of discovery lives on in all the men and women who have devoted their lives to exploring the unknown. That legacy will endure - sparked by a man who taught us the enormous power of one small step."