Just as the Sun is revving up for another run toward solar maximum, a "veteran" spacecraft is passing over our star's north pole.

Ulysses' solar orbit

The Ulysses spacecraft, launched in 1990, is making its third (and likely final) pass over the Sun's polar regions. Click on the image for a larger view.

Source: European Space Agency

From a maximum solar latitude of 80° (which it reached this week) and at a safe distance of some 200 million miles, Ulysses will try to discern differences between the Sun's north and south poles. It swept over the southern region about this time last year. This solar probe will also determine what's changed, if anything, since its last north-polar pass seven years ago.

Built by the European Space Agency, with scientific collaboration from NASA, Ulysses rocketed away from the Sun, toward Jupiter, in October 1990. After leaving Earth, the craft made a close flyby of Jupiter in February 1992 that redirected it back toward the Sun on a new, highly inclined, 6.2-year orbit. Its first polar sweep came in 1994–95, when the Sun was near the minimum of its 11-year activity cycle, and again in 2000–01, during the most recent solar maximum.

You'd think that that Sun's top and bottom would have identical characteristics, but not so. During its mid-1990s pass, Ulysses found that the coronal gas over the northern pole was roughly 80,000°F cooler than the southern one. At that time Ulysses also discovered that the Sun's magnetic equator was 10° south of its rotational equator.

ESA's website has more details about what's expected during Ulysses's third and likely final mad dash under and over the Sun.


Image of Dave GIll

Dave GIll

January 26, 2008 at 7:43 pm

Hi, Kelly

A little off topic - but is there a revised edition of "The New Solar System" planned? I've purchased 3 of the 4 editions over the years, and the 4th is getting a little long in the tooth - especially given recent missions.

Just curious if I should start saving my pennies.


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