Sungrazer

Credit: LASCO, SOHO Consortium, NRL, ESA, NASA

Explanation: Arcing toward a fiery fate, this Sungrazer comet was recorded by the SOHO spacecraft’s Large Angle Spectrometric COronagraph (LASCO) on Dec. 23rd, 1996. LASCO uses an occulting disk, partially visible at the lower right, to block out the otherwise overwhelming solar disk allowing it to image the inner 5 million miles of the relatively faint corona. The comet is seen as its coma enters the bright equatorial solar wind region (oriented vertically). Spots and blemishes on the image are background stars and camera streaks caused by charged particles. Positioned in space to continuously observe the Sun, SOHO has detected 7 sungrazing comets. Based on their orbits, they are believed to belong to a family of comets created by successive break ups from a single large parent comet which passed very near the sun in the twelfth century. The bright comet of 1965, Ikeya-Seki, was also a member of the Sungrazer family, coming within about 400,000 miles of the Sun’s surface. Passing so close to the Sun, Sungrazers are subjected to destructive tidal forces along with intense solar heat. This comet, known as SOHO 6, did not survive.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

Exploring Comet Tails

Image Credit & Copyright: Joe Orman

Explanation: Comets are known for their tails. In the spring of 1997 and 1996 Comet Hale-Bopp (above) and Comet Hyakutake gave us stunning examples as they passed near the Sun. These extremely active cometswere bright, naked-eye spectacles offering researchers an opportunity to telescopically explore the composition of primordial chunks of our solar system by studying their long and beautiful tails. But it has only recently been discovered that surprising readings from experiments on-board the interplanetary Ulysses probe which lasted for several hours on May 1, 1996, indicate the probe passed through comet Hyakutake’s tail! Ulysses experiments were intended to study the Sun and solar wind and the spacecraft-comet encounter was totally unanticipated. Relative positions of Ulysses and Hyakutake on that date indicate that this comet’s ion tail stretched an impressive 360 million miles or about four times the Earth-Sun distance. This makes Hyakutake’s tail the longest ever recorded and suggests that comet tails are much longer than previously believed.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)