Sunspot 930 erupting on December 13. —Photo courtesy of SOHO (Solar and Heliospheric Observatory

Save our skies

Be a considerate neighbor: Reduce nighttime glare. Shield all your outside lights downward (or turn them off completely) and enjoy the beautiful, starry night sky.

January 2007 night sky

—CHARLIE CHRISTMANN
SOLAR OUTBURST
Okay, I know the Sun is not in the night sky, but it is, after all, a star. And this star had a tantrum in December. Early in the month, the Sun's rotation brought a large sunspot, number 930, into view. On December 5, with the spot just on the edge of the solar disk, 930 unleashed a gigantic X-9 solar flare. On December 6 it again let go with an X-6 flare. Neither of these was directed toward Earth. But the one on December 13 was another story. That flare was only an X-3, but it was aimed directly at Earth. On the evening of December 14, the Aurora, or northern lights, which are normally confined to Alaska and Canada, could be seen as far south as Arizona and New Mexico.

Solar flares are gigantic explosions from the surface of the Sun, originating near a sunspot. In a matter of just a few minutes they release as much energy as a billion megatons of TNT. Solar scientists classify solar flares into three main categories, depending upon the strength of the x-rays emitted from them. C-class flares are hardly noticeable on Earth. M-class flares are medium-sized; they can cause brief radio blackouts and affect Earth's polar regions. Minor radiation storms can sometimes follow an M-class flare. X-class flares are big. They are major events that can trigger planet-wide radio blackouts and long-lasting radiation storms. On the surface of our planet, our atmosphere protects us from the radiation, but in space it is a different matter.

X-rays from a flare will hit Earth in about eight minutes, but the charged gas, called plasma, ejected with the flare takes one to three days to reach earth, some ninety-three million miles away. Most plasma clouds give us a glancing blow, but when the origin, as with sunspot 930 on December 13, is pointed at Earth, flares cause havoc in space. Orbiting satellites can be damaged, disrupting telephones, pagers, television, and other communications from space. The residents of the International Space Station were ordered to take shelter in a hardened section of the station to protect them from the radiation. Communications with the fleet of satellites and rovers on Mars were also disrupted. On Earth, when the brunt of the plasma cloud hit our planet, shortwave communications in Asia and the western Pacific were disrupted.

Power fluctuation in the power grid on Earth is another concern. Previous flares have caused wide-scale electrical blackouts. This is caused by the Earth’s protective magnetic field’s absorbing energy from the flare's plasma cloud and ringing like a bell. As the magnetic field oscillates, it induces extra large currents in power lines, overloading transformers, and causing protective systems to shut off the power.

The December 13 flare also may have caused a problem with the ISS attitude-control system. Normally, gyroscopes keep the station stable relative to Earth and keep it from tumbling. The energy from the solar flare probably caused the upper atmosphere to heat up and expand further into space. As the rarified air expanded, it caused more drag than normal on the station, temporarily making the system work harder to maintain its attitude.

All of this activity is happening at what is known as the solar minimum—when the Sun is supposed to be calm and quiet. The Sun goes through an eleven-year cycle of high and low activity. Approximately every eleven years, the magnetic field of the Sun weakens, and then changes direction. At the weakest point in the cycle, the Sun often has few or no visible sunspots. We are currently at the low point in the cycle. As for the next solar cycle, cycle 24, scientists at the National Center for Atmospheric Research, in Bolder, Colorado, think it will start late in 2007 or early 2008, which is about six to twelve months later than a cycle would normally start.

This cycle is expected to peak sometime in 2012. This is when the Sun should be most active. The NCAR team predicts the next cycle will be 30-50 percent more intense than the current cycle. That could be bad news for NASA's astronauts and satellite operators, but great for seeing northern lights here in New Mexico.

The Planets and the Moon

• Mercury will be in the Sun’s glare until late in the month, when it will be setting in the evening just after sunset.
• Venus is the evening star, shining bright in the west after sunset. A thin sliver Moon joins Venus on the January 20.
• Mars is visible low in the east about an hour before sunrise.
• Jupiter rises in the east about two and a half hours before sunrise.
• Saturn will rise in the east around 8:30 pm this month. A crescent Moon joins Saturn on January 6.
• The Moon will be full on January 3. It will be at its most northerly position in its orbit and appear exceptionally high in the sky. The new moon is on January 19.

If you have a question or comment for Charlie, you may e-mail him, at
k5cec@yahoo.com.