Return of the Comet: 96P Spotted by ESA, NASA Satellites

The ESA (European Space Agency) and NASA mission SOHO — short for Solar and Heliospheric Observatory — got a visit from an old friend this week when comet 96P entered its field of view on Oct. 25, 2017. The comet entered the lower right corner of SOHO’s view, and skirted up and around the right edge before leaving on Oct. 30. SOHO also spotted comet 96P in 1996, 2002, 2007 and 2012, making it the spacecraft’s most frequent cometary visitor.

At the same time, comet 96P passed through a second NASA mission’s view: STEREO — short for Solar and Terrestrial Relations Observatory — also watched the comet between Oct. 26-28, from the opposite side of Earth’s orbit. It is extremely rare for comets to be seen simultaneously from two different locations in space, and these are the most comprehensive parallel observations of comet 96P yet. Scientists are eager to use these combined observations to learn more about the comet’s composition, as well as its interaction with the solar wind, the constant flow of charged particles from the Sun.

Both missions gathered polarization measurements of the comet; these are measurements of sunlight in which all the light waves become oriented the same way after passing through a medium — in this case, particles in the tail of the comet. By pooling the polarization data together, scientists can extract details on the particles that the light passed through.

Read more at NASA/Goddard Space Flight Center

Image: The comet entered the bottom of STEREO's view and crossed it diagonally before leaving on Oct. 28. Most of the corona has been suppressed in order to bring out the comet, leaving only the dynamic flow of the solar wind. (Credit: NASA's Goddard Space Flight Center/STEREO/Bill Thompson/Joy Ng)