Astronomy Notes

March 10, 2006: It’s official, Solar minimum has arrived. Sunspots have all but vanished. Solar flares are nonexistent. The sun is utterly quiet.

Like the quiet before a storm.

This week researchers announced that a storm is coming–the most intense solar maximum in fifty years. The prediction comes from a team led by Mausumi Dikpati of the National Center for Atmospheric Research (NCAR). “The next sunspot cycle will be 30% to 50% stronger than the previous one,” she says. If correct, the years ahead could produce a burst of solar activity second only to the historic Solar Max of 1958.

Dikpati’s prediction is unprecedented. In nearly-two centuries since the 11-year sunspot cycle was discovered, scientists have struggled to predict the size of future maxima—and failed. Solar maxima can be intense, as in 1958, or barely detectable, as in 1805, obeying no obvious pattern.

The key to the mystery, Dikpati realized years ago, is a conveyor belt on the sun.

The sun’s conveyor belt is a current, not of water, but of electrically-conducting gas. It flows in a loop from the sun’s equator to the poles and back again. Just as the Great Ocean Conveyor Belt controls weather on Earth, this solar conveyor belt controls weather on the sun. Specifically, it controls the sunspot cycle.

Solar physicist David Hathaway of the National Space Science & Technology Center (NSSTC) explains: “First, remember what sunspots are–tangled knots of magnetism generated by the sun’s inner dynamo. A typical sunspot exists for just a few weeks. Then it decays, leaving behind a ‘corpse’ of weak magnetic fields.”

Enter the conveyor belt.

Right: The sun’s “great conveyor belt.”

“The top of the conveyor belt skims the surface of the sun, sweeping up the magnetic fields of old, dead sunspots. The ‘corpses’ are dragged down at the poles to a depth of 200,000 km where the sun’s magnetic dynamo can amplify them. Once the corpses (magnetic knots) are reincarnated (amplified), they become buoyant and float back to the surface.” Presto—new sunspots!

Source: Solar Storm Warning

Sunspots come and go with an 11-year rhythm called the sunspot cycle. At the cycle’s peak, solar maximum, the sun is continually peppered with spots, some as big as the planet Jupiter. But for every peak there is a valley, and during solar minimum months can go by without a single sunspot.

“That’s where we are now—at minimum,” says Hathaway.

Actually, we’re at the beginning of the minimum. February 2006 was the first month in almost ten years with mostly no sunspots. For 21 of February’s 28 days, the sun was blank. Hathaway expects this situation to continue for the rest of 2006.

No sunspots means low solar activity. Sunspots are sources of solar flares and coronal mass ejections that can disrupt radio communications and even cause power outages on Earth during severe magnetic storms. These problems should subside during the year ahead. Auroras, a beautiful side-effect of magnetic storms, should subside, too. “Too bad,” says Hathaway, who enjoys Northern Lights.

By the way, solar storm is coming soon.

Summarised from Solar Minimum has Arrived

NASA and the European Space Agency released one of the the largest and most detailed photos ever seen of a spiral galaxy beyond the Milky Way on 27 February 2006. The image shows the glorious face-on spiral M101, located 25 million light-years from Earth in Ursa Major off the handle of the Big Dipper. The image is a mosaic of 51 Hubble Space Telescope frames and several ground-based shots. The Hubble images used to make this 16,000-by-12,000-pixel composite were assembled from archival data, which were taken for a variety of research projects dating from 1994 to 2003. The galaxy itself is roughly twice the size of our Milky Way and contains about 1 trillion stars.

You’re advised to visit the press released website for higher resolution pictures.