seeing with different eyes

We’ve been going to Benjamin Dean lectures on and off since the kids were tiny. It’s pretty cool that our youngest, nigh-adult child now enjoys coming with us. Last month we looked at the Galilean moons, including Ganymede with its own magnetosphere and our beloved Europa. This month Stanford professor Susan Clark walked us through the magnetic fields in the interstellar medium (ISM), the dust and gas between the stars.

She was charmingly annoyed about this name. “I’m pretty sure oceanographers don’t study ‘the stuff between the whales.’ I don’t think atmospheric scientists study ‘the stuff between the birds.'” To be fair, she acknowledged, the parts of ISM that are dust show up as black blobs in visible light, like Barnard 68. But if your eyes could see into the infrared spectrum, you would see the stars beyond.

One cool thing about the dust is that its particles are amorphous; another cool thing is that they spin. As they spin, they align with magnetic fields. Because they’re aligned, they polarize the light from the stars behind them, and the heat radiation they emit. So that by examining the polarization of that distant light and heat – by seeing with different eyes – amazing observatories like Planck and Arecibo and SOFIA can map the magnetic fields between the stars. (That main image got projected onto the dome of the Morrison Planetarium. It was astounding. Collective intake of breath.)

Of course the Planck and SOFIA missions have ended, and Arecibo suffered catastrophic mechanical failure. “Everything I love…” said Professor Clark sorrowfully. All eyes turn to the Five-hundred-meter Aperture Space Telescope. There is so much more to learn! Very good science lectures are like being at a party listening to someone absolutely fascinating hold forth on their field of special interest; they’re like touching grass, except the grass is interstellar space. They’re delightful.

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