spaceSpace and PhysicsspaceAstronomy

The Sun's Bottom Is Slowly Being Revealed For The First Time


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockMay 18 2022, 16:50 UTC
The South Pole of the Sun. Image Credit: ESA & NASA/Solar Orbiter/EUI Team

The South Pole of the Sun. Image Credit: ESA & NASA/Solar Orbiter/EUI Team

A curious fact about the Sun is that despite our detailed study over the centuries, we have never seen its poles. Luckily, we have a mission to do that and more. The European Space Agency’s (ESA) Solar Orbiter is imaging the Sun like never before, and its first close passage revealed new properties of our star and started to bring the poles into view.

The planets (and most of the spacecraft we send to space) tend to orbit in a very narrow plane around the equator of the Sun. This doesn’t allow for a view of solar poles – so using the gravitational pull of Venus, Solar Orbiter’s inclination will be raised higher and higher. The current inclination of Solar Orbiter with respect to the equator of the Sun is 4.4 degrees, and it is expected to double at the next flyby of Venus in September. 


While we are still a few years away from a downward look onto the poles, the first perihelion – closest point to the Sun – of Solar Orbiter on March 26 brought its first picture of the majorly underexplored southern polar region of the Sun.

Understanding the complexity of the magnetic field at the Sun’s poles might provide clues on the solar cycle, the 11-year period (roughly) in which the Sun’s activity waxes and wanes. In its fourth passage by Venus in February 2025, the inclination of the orbit will be raised to 17 degrees. Then in December 2026, after another passage, it will get to 24 degrees. That will be the beginning of the “high-latitude” mission.

“We are so thrilled with the quality of the data from our first perihelion,” Daniel Müller, ESA Project Scientist for Solar Orbiter, said in a statement. “It’s almost hard to believe that this is just the start of the mission. We are going to be very busy indeed.”

The Solar hedgehog spotted by Solar Orbiter after perihelion. Image Credit: ESA & NASA/Solar Orbiter/EUI Team

While we are still not peering down onto the poles just yet, the spacecraft is delivering cutting-edge data on the Sun with its ten instruments. Among its recent observation the so-called “hedgehog” – a 25,000 kilometer (15,500 mile) plasma feature made of hot and cold gas spikes spreading in many different directions. 

“Even if Solar Obiter stopped taking data tomorrow, I would be busy for years trying to figure all this stuff out,” explained David Berghman, from the Royal Observatory of Belgium, and the Principal Investigator (PI) of the Extreme Ultraviolet Imager (EUI) instrument.

During the perihelion, Solar Orbiter was 47.9 million kilometers (29.7 million miles) from the Sun, that’s roughly 69 times the radius of the Sun. Being so close to the Sun, its heat shield registered a temperature around 500°C (932°F) which was well dissipated without cooking the instruments inside. Solar Orbiter is a collaboration with NASA.

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