SOHO Tallies Its 1500th Comet

Solar scientists from Europe and the U.S. have had it good since 1995. That's when the Solar and Heliospheric Observatory (SOHO) began conitnuous monitoring of the Sun from space at all kinds of wavelengths. Results from its 12 instruments have revolutionized much of what's known about our star.

SOHO's 1500th Comet
SOHO’s 1500th comet was discovered on June 25th in images captured by the Large Angle and Spectrometric Coronograph (LASCO), one of 12 instruments on board. Click on the image to see an animation of the comet in motion.
ESA / NASA / SOHO Consortium
But little did the SOHO scientists realize that their solar sentry would become the most prolific comet discoverer in history. As of June 25th, SOHO's tally has reached 1,500. Who knew!?

It turns out that a profusion of small comets swarms near the Sun, undetectable from Earth, as part of what's called the Kreutz group — fragments from a large body that veered too near the Sun centuries ago and broke apart. Roughly 85% of SOHO's comets come from this one breakup.

As each fragment plunges inward, the Sun's energy causes its ice and dust to boil off into space, creating a flashy but short-lived display. But it's usually a one-time-only performance: passing just a million miles from the solar surface at perihelion, few of these errant icebergs survive.

So who discovers all these Sun-grazing comets? Amateur astronomers mostly. A dedicated worldwide group scans the SOHO images as they're radioed to Earth for UFOs (Unidentified Frying Objects). A veteran Kreutz-chaser, Rob Matson, once discovered five SOHO comets in one day.

You can get in on the action too — mission scientists have set up a special website to get you started. Happy hunting!