SOHO spacecraft spots comet 96P, a return visitor

Nov. 3 (UPI) -- Comet 96P has returned. The comet as spotted by the Solar and Heliospheric Observatory satellite, a joint mission operated by NASA and the European Space Agency.

As revealed in a blog post published by NASA on Friday, the comet moved into view of SOHO on Oct. 25 and exited frame on Oct. 30.

SOHO was launched in 1996, and though its main task is to study the sun, it's found time over the last two decades to discover some 3,000 comets. Of all those comets, only some are recurring visitors, and 96P is the most frequent guest, having previously made appearances in 1996, 2002, 2007 and 2012.

Comet 96P/Machholz was originally spotted on May 12, 1986, by Donald Machholz, an amateur astronomer. Machholz spied the short-period sungrazing comet from Central California's Loma Prieta using only binoculars.

Amazingly, comet 96P's latest perihelion, the portion of its orbit nearest to the sun, was also spotted by another spacecraft, NASA's Solar and Terrestrial Relations Observatory, or STEREO. The comet completes an orbit every 5.24 years and travels within a uniquely close 11 million miles of the sun during its perihelion.

Astronomers hope to combine the data collected by SOHO and STEREO to discern new details about the comet's composition and study how the icy body reacted with high-energy particles streaming from the sun as it rounded the fiery orb.

Both spacecraft were able to observe polarized light coming from the comet's tail. As a light wave passes through a medium, like a comet's tail, its spin becomes oriented in a uniform direction. The polarization can reveal details about the molecules in the medium through which the lightwave passed.

"Polarization is a strong function of the viewing geometry, and getting multiple measurements at the same time could potentially give useful information about the composition and size distribution of the tail particles," William Thompson, NASA scientist and STEREO chief observer at Goddard Space Flight Center, said in a news release.

The last time astronomers observed comet 96P, they found two fragments leading the main body, suggesting the comet was breaking apart and evolving. A third fragment was spotted on its latest pass.

As larger comets break apart, they form newer comets with related compositions. These lineages are organized into families. Researchers believe comet 96P has fathered two comet families, each with unique compositions. The fragments of some of 96P's offspring collide with Earth's atmosphere, producing meteor showers. Scientists hope further study the 96P will help them better understand how comets evolve and spawn families.