Published: 07:08 AM, Thu May 26, 2011
Backyard Universe: Solar activity firing up
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Staff photo by Johnny Horne
[+] click to enlarge

A large sunspot group appearing on the sun in July 2004 is shown in the overall image of the sun at left and close-up in the photo at right. Both photos were made using a telescope fitted with a solar filter. Sunspots can spawn solar flares that can trigger displays of the aurora borealis or Northern lights.






Johnny Horne

You may not have even noticed, but the sun has recently become more active.
This has nothing to do with the 90-degree days we've had this week, which is a seasonal effect. I'm talking about activity on the sun 93 million miles away.
Activity on the sun, including sunspots, solar flares and large-scale events, called coronal mass ejections, ebb and flow over an 11-year cycle. The current cycle is building after one of the quietest minimums on record. Since December 2008, solar activity has been gradually increasing.
Sunspots, which are dark, cooler regions on the sun's surface, are the most easily visible indicator of solar activity. Sunspots present on the sun's earthward-facing side are easily visible from Earth if we use a suitably safe filtered telescope. You should never try to observe the sun through a telescope that isn't equipped with a safe solar filter.
Nowadays, there's an even better way to keep track of sunspot activity, even when it's cloudy. The Internet is a gold mine of solar activity information and spaceweather.com posts a current high-resolution image of the sun taken every day. The pictures this week show a tiny sunspot near the center of the sun's face.
Increased solar activity can produce vivid displays of the aurora borealis, or the Northern lights, and the biggest solar events can even trigger aurora displays visible here in the Southern United States. Aurora displays happen when charged particles expelled during solar activity interact with the Earth's atmosphere and magnetic field. We had stunning displays of the aurora here in 2001 and 2003.
Seeing Endeavour
The current space shuttle Endeavour mission is the last for that particular shuttle and the next to last space shuttle mission period. That means the days are numbered when we can watch an orbiting shuttle passing overhead: Endeavour and the final shuttle flight this summer heading for the International Space Station.
Obtaining predictions for the space shuttle and International Space Station (ISS) is easy using heavens-above.com. You'll have to get up before the sun to see the next two good appearances, though. Don't expect to see Endeavour and the space station cross the sky as separate objects for the next few days because they are docked together and appear as one spacecraft.
Heavens-above.com lists an upcoming local pass of the combined Endeavour and ISS Friday morning at 5:14 a.m. across the northwestern sky and a Sunday morning pass across the northern sky at 4:25 a.m.
Endeavour is scheduled to land at Kennedy Space Center in Florida at 2:32 a.m. on Wednesday. A day or two before that landing, after Endeavour has left the ISS, Heavens-above.com will list Endeavour and the ISS as separate objects as they move across the sky.
Close call this fall
This next astronomical event is later in the year, but between now and November you should hear about a large asteroid that will make a close pass by us this fall.
Asteroid 2005 YU55, a "near earth" asteroid some 400 yards across, will actually pass closer to us than the moon's orbit on Nov. 8. That makes it one of the largest objects we've known about in advance that will pass so close to us.
Amateur astronomers with moderate size telescopes will be able to spot 2005 YU55 if they know where and when to look, but it won't appear bright enough to be seen with the unaided eye or small telescopes or binoculars, even when it's closest to us.
By the way, as of May 24 there are 1,224 "potentially hazardous" asteroids larger than 100 meters across that pass very close to Earth, according to spaceweather.com. None are known to be on a collision course with us, but new objects are being found all the time.
If you have a question about astronomy, send it to Backyard Universe, P.O. Box 849, Fayetteville, NC 28302 or e-mail hornej@fayobserver.com.