We Earthlings see the sun every day of our lives—but gaining a truly new view of our star is a rare and precious thing. So count your lucky stars: for the first time in history, scientists have photographed one of the sun’s elusive poles.
The images come courtesy of a spacecraft called Solar Orbiter. Led by the European Space Agency (ESA) with contributions from NASA, Solar Orbiter launched in February 2020 and has been monitoring our home star since November 2021. But the mission is only now beginning its most intriguing work: studying the poles of the sun.
From Earth and spacecraft alike, our view of the sun has been biased. “We’ve had a good view of centermost part of the sun’s disk,” says Daniel Müller, a heliophysicist and project scientist for the mission. “But the poles are effectively not visible because we always see them almost exactly edge-on.”
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We began getting a better perspective earlier this year, when Solar Orbiter zipped past Venus in a carefully choreographed move that pulled the probe out of the solar system’s ecliptic, the plane that broadly passes through the planets’ orbits and the sun’s equator. (The new views show the sun’s south pole and were captured in March. The spacecraft flew over the north pole in late April, Müller says, but Solar Orbiter is still in the process of beaming that data back to Earth.)
Leaving the ecliptic is a costly, fuel-expensive maneuver for spacecraft, but it’s where Solar Orbiter excels: By the end of the mission, the spacecraft’s orbit will be tilted 33 degrees with respect to the ecliptic. That tilted orbit is what allows Solar Orbiter to garner unprecedented views of the sun’s poles.
For scientists, the new view is priceless because these poles aren’t just geographic poles; they’re also magnetic poles—of sorts. The sun is a massive swirl of plasma that produces then erases a magnetic field. This is what drives the 11-year solar activity cycle.
At solar minimum, the lowest-activity part of the cycle, the sun’s magnetic field is what scientists call a dipole: it looks like a giant bar magnet, with a strong pole at each end. But as the sun spins, the roiling plasma generates sunspots, dark, relatively cool patches on the sun’s surface that are looping tangles of magnetic field lines. As sunspots arise and pass away, these tangles unfurl, and some of the leftover magnetic charge migrates to the nearest pole, where it offsets the polarity of the existing magnetic field. The result is a bizarre transitional state, with the sun’s poles covered in a patchwork of localized “north” and “south” magnetic polarities.
In the solar maximum phase (which the sun is presently in), the magnetic field at each pole effectively disappears. (It can be a bumpy process—sometimes one pole loses its charge before the other, for example.) Then, as years pass and solar activity gradually declines, the continuing process of sunspots developing and dissipating creates a new magnetic field of the opposite charge at each pole until, eventually, the sun reaches its calm dipole state again.
These aren’t matters of academic curiosity; the sun’s activity affects our daily lives. Solar outbursts such as radiation flares and coronal mass ejections of charged plasma can travel across the inner solar system to reach our neighborhood, and they’re channeled out of the sun by our star’s ever changing magnetic fields. On Earth these outbursts can disrupt power grids and radio systems; in orbit they can interfere with communications and navigations satellites and potentially harm astronauts.
So scientists want to be able to predict this so-called space weather, just as they do terrestrial weather. But to do that, they need to better understand how the sun works—which is difficult to do with hardly a glimpse of the magnetic activity at and around our star’s poles. That’s where Solar Orbiter comes in.
Most of the spacecraft’s observations won’t reach Earth until this autumn. But ESA has released initial looks from three different instruments onboard Solar Orbiter, each of which lets scientists glimpse different phenomena.
Solar Orbiter’s view of the magnetic fields around the sun’s south pole. Patches of blue and red mark the mixed magnetic fields in this region that characterize solar maximum.
ESA and NASA/Solar Orbiter (CC BY-SA 3.0 IGO)
For example, the image above maps the magnetic field at the sun’s surface. And from this view, Müller says, it’s clear that the sun is at the maximum period of its activity cycle. Heliophysical models predict “a tangled mess of all these different patches of north and south polarity all over the place,” he says. “And that’s exactly what we see.”
As their accordance with theoretical models suggests, the solar poles aren’t entirely mysterious realms. That’s in part because while Solar Orbiter is the first to beam back polar images, it isn’t the first spacecraft to fly over these regions. That title belongs to Ulysses, a joint NASA-ESA mission that launched in 1990 and operated until 2009.
Ulysses carried a host of instruments designed to study radiation particles, magnetic fields, and more. And it used them to make many intriguing discoveries about our star and its curious poles. But it carried no cameras, so despite all its insights, Ulysses left those regions as sights unseen.
Fortunately, heliophysics has grown a lot since those days—and space agencies have learned that, in the public eye, a picture can be worth much more than 1,000 words. The result: Solar Orbiter can finally put the spotlight on the sun’s poles.
