Astronomers have been watching Comet 168P/Hergenrother closely the past couple months since it’s been in outburst and much brighter than expected. There have also been recent reports of fragmentation of the comet’s nucleus.
Heat from the sun causes comet ices to vaporize; the expanding gas can stress a comet’s fragile, icy nucleus, riddling its outer crust with fissures. As fresh ice is exposed, more gas and dust jet outward from the nucleus to swell the comet’s coma or temporary atmosphere. It all adds up to a surge in brightness that can make an otherwise obscure comet brighten enough to see in even a small telescope.
Several photos have been published that may or may not show pieces leaving the nucleus and drifting down the comet’s tail, but the first unequivocal image was released today by a team of amateur astronomers at the Remanzacco Observatory in Italy. The fragment pictured in the photos might be a clue to the comet’s steep rise in brightness that began in late September.
Nick Howes, Ernesto Guido and Giovanni Sostero took numerous exposures using a 79-inch (2.0-meter) telescope in Hawaii. They operated the scope remotely, downloaded the images and processed them to reveal a glowing fragment just south of the bright nucleus. This “chip off the old block” may fragment further and possibly kick up Hergenrother’s brightness another notch. We’ll have to wait and see.
Amateur astronomers with 8-inch or larger telescopes will want to study the comet closely with their highest magnifications that atmospheric seeing (steadiness of the air) will allow in the coming nights. The fragment’s a mere 2 arc seconds across and faint, but there’s a chance it may brighten further and separate from the nucleus, making it easier to spot.
Comet nuclei are delicate creatures subject to fractures and breakups especially when they approach the sun. One of the best examples of a fragmenting comet is 73P/Schwassmann-Wachmann 1. The Hubble image at left shows the break-up best, but fragments could even be seen in amateur instruments.
Hergenrother is receding back into the depths of space, having passed Earth earlier this fall, but it’s still bright enough for scopes 6-inches and up. To keep eyes on the comet, click HERE for a map and more info.