Two visitors from the Oort cloud
Sen—Two comets which began life in the Oort cloud at the outer edge of the Solar System will be paying a visit to our skies during the next year.
Comet C/2011 L4 (PANSTARRS) will make its closet approach to us in March 2013, whilst comet C/2012 S1 (ISON) should be visible in the period November 2013 - January 2014. Both could become bright naked eye objects.
Comet PANSTARRS was discovered by the Panoramic Survey Telescope & Rapid Response System, or Pan-STARRS telescope, in Hawaii, Maui in June 2011. Once the orbit had been established, a network of observers including a team using the Faulkes Telescope from the Remanzacco Observatory in Italy, closely monitored the comet, looking at its evolution as it approached the Sun.
It is expected to make its nearest approach to Earth on March 5 coming within about 100 million miles of Earth, skimming inside the orbit of Mercury. On March 10, the comet makes its closest approach to the sun. The best time to see it should be at sunset on March 12 and 13, not far from the crescent moon.
Comet ISON was discovered by Russian astronomers Vitali Nevski and Artyom Novichonok in September 2012, using the International Scientific Optical Network (ISON), near Kislovodsk. Again follow-up measurements were taken by the team from the Remanzacco Observatory.
Nick Howes, Pro Am Programme Manager for the Faulkes Telescope project who is also currently working as a research associate for the Lowell LARI project on Trans Neptunian Objects (TNOs) told Sen, "As one of the first teams in the world to image it whilst it was still on the minor planet centre's near Earth object confirmation list (before it was known and classified as a comet), we noticed how bright it could potentially get almost instantly. Care with estimations though has to be taken, comets, as David Levy famously stated are "like cats" (they have tails and are unpredictable)"
ISON is due to approach within 800,000 miles (1.2 million km) of the the Sun on November 28 and make its closest approach to Earth on December 26, coming within 40 million miles (64 million km) of us.
This could be both comet's first trip through the inner solar system, meaning their pristine surface has a higher probability of being laden with volatile material just waiting to be released when the sun's energy heats it up. Of course the comets could fade or break apart but many are hailing ISON in particular as the 'Comet of the Century' and claiming it could shine as bright as the moon and even be visible in daylight.
Nick Howes advises caution, "Our magnitude estimations are below what others are saying, by several magnitudes. The hype in the press has made this comet very prominent in the public imagination, but it could be a great big nothing, nobody knows."
NASA managed to image comet ISON using their Deep Impact spacecraft on January 17 and 18 and they hope to observe it from the surface of Mars using Curiosity's Mastcam, as well as from orbit with NASA’s Mars Reconnaissance Orbiter (MRO) and with the Lunar Reconnaissance Orbiter (LRO).