ISONblog

  • July 31, 2013

    Finding ISON

    by Josh Sokol

    At 4 a.m. Artyom Novichonok and Vitali Nevski were still wide awake.

    The early hour was not so unusual for astronomers – a nocturnal bunch, out of necessity – but on this particular morning, clouds blocked the stars above the ISON Observatory near Kislovodsk, Russia. One night earlier, Nevski had noticed a bright speck of light drifting against a field of stars. It moved a lot like a comet, but they couldn’t be sure. The Maidanak Observatory in Uzbekistan had kindly obliged to follow up on the mysterious object with a larger telescope. And so Nevski and Novichonok spent the night poring over old materials, speculating on the orbit of this potential comet, and refreshing their e-mail inboxes. Waiting.

    ***

    Like many other astronomers, the discoverers of what we now call Comet ISON were attracted to the field after being drawn to the sky as children. “Back then, I simply liked to look at it; see its bottomless, endless stretch,” says Novichonok. “I spent my childhood away from the lights of the city, in a village which had a population of 2,000. The sky above our village back then was beautiful.”

    Both astronomers cut their teeth finding asteroids. In the 1990s, Nevski assembled his own observatory. Over the next two decades, he transitioned from a serious asteroid-hunting hobbyist to a professional researcher with the International Scientific Optical Network (ISON). Meanwhile, Novichonok made his first asteroid discoveries using the Tzec Maun Observatory. But asteroids were stepping stones, just “practice grounds” for finding the small, scattered objects left over from our solar system's infancy.  “I specifically wanted a comet,” says Novichonok, who grew up reading about famous hunters of the "tailed guests."

    They had been burnt before. Twice, Nevski was on the cusp of discovering a comet, only to be narrowly beaten to publication. Novichonok had credit for an earlier comet, but the discovery had been tainted by a disagreement over what to name it.

    Being the first to find a comet takes a lot: access to professional-quality telescopes, analysis software, and either the good luck to look in the right place at the right time or the fiscal resources to look in many places all the time. But perhaps above all else, staking a claim to a new comet is a quick-draw game. It takes speed. So on the morning of September 22, Nevski and Novichonok anxiously awaited higher-resolution images of their comet candidate from the Maidanak Observatory.

    ***

    The night before, when they had first noticed the comet, was intermittently cloudy. After 10 clear nights of rote survey observations, Nevski and Novichonok decided to try something new. They picked a patch of sky at the intersection of the constellations Gemini and Cancer, instructing the ISON telescope to begin an automated search sequence. Their target: anything that moved.

    Later, with the images all taken, Novichonok rested. Nevski loaded his data into the asteroid-discovery software CoLiTec. Since asteroids (and comets) travel along orbits in our solar system, they don’t stay lined up with the stars, which merely arc across the sky as the Earth spins from night to day. A star that appears to move relative to the other stars, then, is not a star at all: it’s likely an asteroid … or something  even more exotic.

    One of the images in which Comet ISON (circled) was discovered. Image
    credit: Vitali Nevski
     

    The analysis turned up one such object, which moved, but it moved slowly – too slow to be part of the asteroid belt. It was thus probably farther away. “At that moment, I was beginning to understand that such a slow-moving object did not belong to the asteroid belt and should be located far away from the orbit of Jupiter,” writes Nevski in an online account (in Russian) of the discovery. “And considering its brightness…my heart jolted – it was a comet!”

    But the discovery needed additional confirmation. To qualify as a comet, an object should be extended in the sky – not just a dot. Asteroids and comet nuclei are roughly the same size and appear as tiny points of light in our telescopes. It’s the comet’s ephemeral, gaseous coma, stretching out from the nucleus, which differentiates it from an asteroid. The ISON telescope was too small to detect a coma, so they reached out to Maidanak for help.

    The confirmation image from Maidank. Comet ISON, marked by crosshairs, is
    clearly trailed by a hazy coma. Image credit: Vitali Nevski

    The rest, as they say – figuring out ISON’s orbit, the “comet of the century” hype, #WillItBreakUp, ISONblog – is astro-history. The Maidanak images finally came, showing the much hoped-for coma. Hastily Nevski and Novichonok fired off a message to the International Astronomical Union, registering their finding, and after a few more agonizing hours confirmation arrived. Nobody else had spotted Comet ISON first.

    ***

    As is often the case in science, the ISON discovery happened only with a combination of hard work and serendipity. Nevski estimates he put in over 500 hours of telescope time searching for comets, finally finding success only with professional equipment. Even with their effort, they were still small fish in the comet-hunting pond, notes Novichonok. “Logically, we weren’t supposed to have discovered a comet.”

    Their timing was beyond fortunate. About nine months earlier, two different, high-profile programs had captured pictures of ISON without realizing it. Later, once ISON was known, astronomers were able to locate the comet in these “pre-covery” images. The real lucky break, though, was this: only 30 hours after Nevski and Novichonok’s randomly-picked search pattern captured ISON, the same patch of sky was scanned by the automated survey LINEAR. Immediately, LINEAR noticed ISON – just a hair’s width too late.

    With the languid unfurling of its tail, ISON could dominate night skies for weeks. But that’s only if the comet survives its close brush with the Sun. If not, ISON could soon be forgotten, or worse: like Kohoutek, it could be relegated to an eternal hall of shame, the Valhalla for comets that underwhelm despite high expectations.

    Although they continue to measure the comet’s brightness, Nevski and Novichonok are now spectators like the rest of us, skywatchers at ISON’s mercy. When asked what he anticipates, Novichonok is optimistic. “I hope that the comet will become relatively bright in its perihelion. I think that we have good chances of seeing a sky show this December.”

    Nevski is more reserved. “The fact that the comet ISON is now famous throughout the world does not make me particularly pleased – it is all being rather blown out of proportion by journalists,” he says. “It's not definite that we will witness a bright comet. It is their nature that these minor bodies are very unpredictable.”

    ***

    In the breaking dawn of September 23, though, Comet ISON’s ultimate fate hardly mattered. As Nevski went to rest, Novichonok reflected on the moment. “I went outside; it was already sunrise. I walked around the telescope, around the control building. Inside there was a feeling of freedom, which added to the morning view of Mount Elbrus,” he said.

    “We did it.”

     

    Special thanks to N. L. Zakamska and E.V. Zheleznyakova for providing translation and additional research for this piece.