Ulysses Confirms Poles of Sun Have Different Temperatures

The north and south poles of the Sun are not at the same temperature, they vary by roughly 7 to 8 percent, or 80,000 degrees Kelvin.

The astute reader (which is of course you, since you’re reading my blog) may be asking, “Wait a minute, did you say 80,000 degrees? I thought the Sun was only about 5,000 degrees Kelvin.”

It is true that the surface of the Sun is roughly 5,000 degrees, but the temperatures measured by Ulysses are that of the corona and solar wind, where charged particles are constrained by strong magnetic fields resulting in much higher temperatures, on the order of 1.5 million degrees kelvin.

Ulysses, a spacecraft designed to fly over the poles of the Sun, has recently confirmed that the temperature of the one pole is about 80,000 degrees cooler than the other. It doesn’t matter whether you specify north or south magnetic pole since they switch polarity every 11 years.

What would make the sun lopsided in this way?

There’s still no definitive answer to that question, but now at least researchers know the effect is real. Ulysses has returned to the sun’s South Pole in 2007 and “recent observations show that the average temperature … is virtually identical to what we saw 12 years ago,” says Gloeckler.

Here’s a schematic of the orbit of Ulysses:

Illustration Credit: NASA/ESA

Image Credit (above left): ESA
Here’s the full press release.

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