Universe Today - November 9, 2001

By analyzing how sound waves travel inside the Sun, a team of scientists have produced a detailed image of the inside of a sunspot. What they found was swirling flows of electrified gas or plasma that create a self-reinforcing cycle, which holds a sunspot together. The data was gathered by the Solar and Heliospheric Observatory (SOHO) spacecraft which is currently positioned about 1.6 million km from Earth.

Some good news: the Earth is less likely to be struck by an asteroid than scientists previously calculated. The odds are only 1 in 5,000 that an asteroid big enough to wipe out civilization will hit the Earth within the next 100 years (much lower than the 1 in 1,500 of earlier estimates). Astronomers from Princeton University used data from the Sloan Digital Sky Survey to calculate that there are 700,000 asteroids in the solar system larger than 1 kilometre; but only a fraction of those will ever cross the Earth's orbit.

The Northern Lights appeared with rare intensity over much of North America this week; they were seen as far South as Georgia and Alabama. Emergency phone numbers received calls from worried skywatchers, thinking this natural lightshow might be some kind of "terrorist thing". The Northern Lights, or aurora borealis, are caused when the Sun's solar wind interacts with Earth's magnetic field. A similar lightshow was also visible in the Earth's Southern Hemisphere.

NASA's High Energy Transient Explorer (HETE) was fortunate enough to record the rare optical afterglow of a gamma ray burst, the most powerful type of explosion known in the universe. The burst occurred on September 21 in the constellation Lacerta, and was located 5 billion light years from Earth. By studying the afterglow, astronomers hope to understand what causes these tremendous explosions - exploding stars, merging black holes, or something completely unpredicted?