Hidden in plain sight along one of the Peninsula’s most popular hiking trails is a geometrically funky tower, where scientists have been quietly collecting solar measurements for nearly 50 years.
Built in 1975, the Wilcox Solar Observatory was part of a Navy project to study the sun’s magnetic field. The sun’s corona spews out a constant stream of charged particles, a solar wind that reaches speeds of up to a million miles an hour as it spreads those particles across our solar system.
Why was the Navy interested in something so solar-related? When the direction of the magnetic field within that solar wind changes, it can reduce the Navy’s ability to communicate with submarines, says Stanford physics professor J. Todd Hoeksema, who leads the university’s Solar Observatories Group, which includes the Wilcox observatory.
For the last four decades, the solar observatory has collected low-resolution maps of the sun’s magnetic field each day, weather permitting. Rain and cloud cover can make those efforts challenging, of course. But on sunny days, a resident scientist — typically, a Stanford physics graduate student — collects solar data, taking measurements for 15 to 20 minutes at a time, three or four times a day to map the field.
It’s a gig that comes with on-site lab housing, a quiet retreat from bustling campus life that’s considered a perk, although Hoeksema recalls being startled by a tarantula on his first night there as a grad student long ago.
Sadaf Kadir works inside the Wilcox Solar Observatory in the hills west of Stanford University, Thursday, Nov. 9, 2023. (Karl Mondon/Bay Area News Group)
Around 30 students have lived at the observatory over the years. (Or rather, 31 — one scientist had a baby during her residency.) Many of those scientists, Hoeksema says, have gone on to careers as solar astrophysicists.
At the moment, physics grad student and resident scientist Sadaf Kadir lives at the observatory with her cat. Several times a day, Kadir climbs the tower to set up instruments, so the sun’s rays hit the lab’s mirrors at the right angle to create a spectrograph capturing details about the solar magnetic field.
The results of her measurements are then reported out at http://wso.stanford.edu, where helioscientists can pore over the data. Laymen can, too, although it makes for a pretty abstruse read.
The non-solar astrophysicists among us can click through to the Stanford Solar Center, a regular people-friendly education link that includes everything from vital solar statistics and physics explainers to instructions for baking scientifically-accurate planet cakes, mantle, core and all. There’s a recipe for solar cupcakes, too, that includes an advisory that despite the sunny yellow crayons we wielded as kids, the sun is actually white.
“Choose your (frosting) color accordingly,” the recipe says.
Sadaf Kadir adjusts the mirrors and lenses at the Wilcox Solar Observatory in the hills west of Stanford University, Thursday, Nov. 9, 2023. (Karl Mondon/Bay Area News Group)
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From the ground, the Wilcox Solar Observatory tower looks rather like the love child of a pyramid and an observatory. It may not be as flashy or prominent as its famous hilltop neighbor, the Dish, but the solar lab has its own historic legacy. After nearly half a century of observations, the lab has collected a consistent body of data scientists use to track the sun’s 11-year solar cycle patterns, Hoeksema says, and learn about space weather and solar wind.
In recent years, heliophysicists have put devices into space to collect more sophisticated measurements, but the Wilcox observatory provides consistency, a long-term solar record that uses the same method as it did half a century ago. Plus, Hoeksema says, it’s more sensitive to weak magnetic fields than other observatories.
Why is all this — this observatory and these measurements — important?
“People assume they know a lot about the sun,” Kadir says. “But there are a lot of open questions.”
Solar activity shapes what’s known as space weather, and that, in turn, can impact communications and GPS systems — technology used by our smartphones and our cars, not just Navy submarines.
And for observers of night sky phenomena, space weather explains why the aurora borealis was visible in the Bay Area and beyond in May, sending otherworld waves of fuchsia and pale green light across the sky in some places. There was a major geomagnetic storm on the sun.