20 Years of Staring at the Sun

On Dec. 2, 1995, the joint ESA/NASA mission SOHO roared into space on an Atlas/Centaur rocket. Four months later SOHO (the Solar and Heliospheric Observatory) fell into its new home, a “halo” orbit 1.5 million kilometers away from Earth in the direction of the Sun. Soon thereafter it began its mission: to observe the Sun with its multitude of detectors, helping us understand our nearest star.

That was nominally a two-year mission. This week, 20 years later, SOHO is still chugging along, celebrating its platinum anniversary.

After more than 7,300 days in space (!!), it’s racked up an amazing amount of science. It’s watched the Sun through nearly two full solar magnetic cycles, mapping sunspots, magnetic activity, flares, prominences, and more. 

To celebrate, NASA put out this lovely video highlighting just a few of the achievements of this mighty observatory:

I can’t say enough about how great this mission is, and what it’s showed us about the Sun. I’ve written about SOHO dozens of times, including some of the topics covered in the video:

• SOHO watched as Comet ISON disintegrated
• In 2003, SOHO saw the most powerful flare in the modern era
• SOHO measurements of Mercury crossing the Sun were used to get the most accurate diameter for our star ever determined
• SOHO spotted a dead comet
• SOHO tracks a comet on a death dive into the Sun
• SOHO observations were used to study sunspots forming while they were still 60,000 km below the Sun’s surface (that still blows me away)
• SOHO, together with SDO and STEREO, tracks an eruptive prominence
• … and roughly a bajillion more. Also be sure to check out the Best of SOHO!

I used to work at NASA Goddard Space Flight Center, literally down the hall from the offices where astronomers studied the Sun, so I have quite a few friends working on this magnificent and venerable observatory. I’m very glad the mission got extended by 1,900 percent! It’s easy to think that missions like SDO (the Solar Dynamics Observatory, which this year celebrated five years in space) replace earlier ones like SOHO, but that’s not the case. They supplement each other, adding to their capabilities, doing more than any single mission can do. 

The Sun is more than the center of our solar system. It is the provider of light, heat, energy, and the anchor that holds all the planets, comets, asteroids, icy Kuiper belt objects, and more under its sway. Its magnetic field directly impacts us here on Earth, affecting our satellites, our communication, even our power grid.

Studying it is one of the smartest things we humans do. With SOHO, and all the other observatories, we study it very, very well. Congratulations to everyone on the SOHO team. And here’s to staring for another two decades into the Sun.