• November 26, 2013

    ISON Update: Outbursts and Activity


    Astronomers around the world are watching Comet ISON now as it approaches the Sun, with varying results. The Transiting Planets and Planetesimals Small Telescope (TRAPPIST) team in Chile reports that ISON's gas production is now about 10 times greater than it was earlier. The prodiguous amount of gas being given off and the related brightness of the comet allow astronomers to better analyze the compositon of the comet's icy nucleus. Astronomers are seeing a lot of water, carbon-bearing molecules, and some ammonia, among other compounds.

    This is exciting for a couple reasons. First, it gives us a look at the composition of the objects of the Oort Cloud, a spherical region of debris near the edge of the solar system. Since the Oort Cloud objects are thought to be left over from the formation of our solar system, this tells us about how our Sun, planets and associated bodies came into existence. Second, astronomers theorize that comets may have helped seed planets with water and the precursors for life. The carbon-based compounds evident in ISON may be evidence for how organics are transported and delivered within the solar system.

    The IRAM telescope in Spain finds ISON's brightness showing signs of fading, indicating that the nucleus is fading or may have already disintegrated. Backing this up are observations by Nicolas Biver that ISON's orbit is lagging slightly behind where it should be at this point in time, indicating that something — could it be a crack-up? — happened to break the comet's stride. But the latest observations from the orbiting Solar Terrestrial Relations Observatory (STEREO) observatory show no change in the comet's coma. If the nucleus were to break apart, it should be apparent by changes in the shape of the cloud of gas and dust around the nucleus.

    What does this all mean for observers on the ground? Well, ISON should be visible now to the naked eye — but unfortunately, it's so close to the Sun at this point that it's very difficult to see. By the time most people could hope to see it, the sky has become bright with morning light. ISON is about to disappear behind the Sun, reemerging in early December. If the nucleus remains intact, we can hope for a handful of viewing days then. In the meantime, join the STEREO Science Center to watch ISON's encounter with the Sun on Nov. 28. You can read about their plans in detail here.