A monster 14 times the size of Earth is creeping across the surface of our nearest star — and astronomers and other skywatchers are delighted, though communications firms and satellite operators remain wary.
The monster is an L-shaped cluster of sunspots, called by scientists "AR 9393." According to NASA, it's the biggest blot to appear on the sun in the past decade, and it promises to create spectacular northern lights this weekend. The display may reach as far south as Utah.
AR 9393 was so huge it could be seen without a telescope, using a special solar filter to protect the eyes. Seen through a telescope equipped with such a protective filter, the "AR 9393" sunspot cluster was only the most awesome of several series of spots.
"The area of the sun designated AR 9393 has been a prolific generator of stormy solar activity, hurling electrified gas toward Earth," said Dolores Beasley at NASA headquarters in Washington, D.C. The spots produced four explosions, called solar flares, which sent storms of high-speed particles into space.
"The largest of the four flares occurred at 4:57 a.m. EST (2:47 a.m. MST) on Thursday, March 29, and was rated as an X-class flare, the most potent designation," she added. "The other three flares were rated M-class, second only to the X-class."
On Wednesday, an eruption near AR 9393 hurled a huge mass of magnetic gas toward Earth, she said. The eruption is called a coronal mass ejection.
Over the weekend, the electric material should impact Earth's upper atmosphere, causing gas in the sky to glow. These glowing streamers, sheets and columns are known as the aurora borealis, or northern lights, as they usually center in the north.
Sunspots are especially big and common because the sun is close to "solar maximum," the time in the sun's 11-year cycle when it is most active. According to Joseph Gurman of NASA's Goddard Space Flight Center in Greenbelt, Md., sunspots with complex magnetic field structures, as in AR 9394, can generate big flares.
"Sure enough, we just had a powerful X-class flare from this area," Gurman said in a NASA press statement.
Sunspots are darker areas of the sun's surface, caused by distortions of the magnetic fields. When solar fares erupt, they can release as much energy as a billion megatons of TNT.
Flares not only cause auroras but also can damage satellites and interrupt radio communications. Big flares can even knock out electrical power.
"It's certainly the biggest one (sunspot) I've seen, if not ever, in the last many years," said Hansen Planetarium's Patrick Wiggins. "It's not often that you get a sunspot that is big enough literally to see with just your eyeball," when shielded, he said.
Chuck Hards, a Salt Lake area amateur astronomer, said photographs taken in past decades show sunspots that could put the present fleet of spots to shame. But this is the biggest in a long time, he added.
"I personally haven't seen a spot that big since the last solar max about 10 years ago," Hards said. "This is really exciting, to see one this big."
Wiggins said Utahns have "a pretty decent chance" to see an aurora because of the activity. When the northern lights dance across the sky, he said, it's because the upper atmosphere in effect "becomes a neon light" with electrical activity exciting gases.
Depending on which gases are stimulated by the solar electricity, he said, the aurora can be of different colors.
Wiggins quickly added what he called "the big caution," which is, "Don't look at the sun without proper filtration. That's not only unwise, it's stupid."
Looking at the sun without the proper protective filters can result in blindness. Damage to the retina may not be obvious until too late, because that part of the eye lacks pain sensors.
Hards said the best way to see an aurora is to get away from city lights. The cluster could cause northern displays for a few nights.
For more about the sunspots and auroras, check out a NASA site on the Internet,www.spaceweather.com/.
E-mail: bau@desnews.com