Even the sun appears headed for a recession.
The Ulysses space probe has detected fewer sunspots, decreased solar winds, and a weakening magnetic field—the lowest solar activity observed in 50 years, NASA scientists said yesterday.
That translates into a shrinking of the heliosphere, the invisible "bubble" of solar wind that extends beyond Pluto and guards the planets—ours included—from bombardment by cosmic rays.
Speaking yesterday at a NASA teleconference, scientists refused to draw conclusions from their observations, especially with respect to whether the changes are influencing Earth's climate.
"That area of science is in the realm of speculation at this point," said Nancy Crooker, a researcher at Boston University.
But David J. McComas of the Southwest Research Institute, who leads one of the experiments onboard Ulysses, called the changes "significant."
"This is a whole-sun phenomenon. The entire sun is blowing significantly less hard than it was 10 to 15 years ago," he said.
"Over the entire record of sun observations, this is the longest prolonged low pressure that we've observed."
Variable Star
Some variance in solar activity is normal for the sun, which has a 22-year magnetic cycle and an 11-year sunspot cycle.
But McComas said in a statement that researchers have been "surprised to find that the solar wind is much less powerful than it had been in the previous solar minimum."
Despite its name, solar wind is actually a stream of charged particles that expands out from the sun.
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