One of the most legendary PR disasters in the history of astronomy happened in 1973 when the world awaited the arrival of comet Kohoutek, discovered by Czech amateur astronomer Luboš Kohoutek early that year. Once the orbit was plotted, astronomers knew that the comet was a first time visitor from the hypothesized Oort Cloud, a gigantic 2 light-year wide freezer containing pristine ices from the early solar system.
Because this was a virgin comet, untouched by intense sunlight for billions of years, the prediction was that it had lots of fresh ices ready to boil off once it entered the inner solar system. It was called the “comet of the century” by one enthusiastic astronomer. The name stuck. People lined up at planetariums and amateur telescope sales soared.
But Kohoutek was a dud, never rising to the expected brightness, though it became a modest naked–eye object. The letdown was such a publicity bust it killed news coverage of comets until the legendary Halley’s comet came along in 1986.
Astronomers were left scratching their heads — what happened?
Now, 40 years later, Comet ISON may solve the mystery. That’s the general consensus of comet scientists, some who started their careers observing Kohoutek. They gathered at a workshop last week at the Johns Hopkins Applied Physics Lab (APL) near Columbia, Maryland, to ponder the comet’s eventual fate. A diverse set of planetary and solar experts began to coordinate an unprecedented global and space based observing strategy for the deep space visitor.
Meeting organizer Casey Lisse of APL kicked off the get-together by suggesting that even if ISON is another Comet Kohoutek that will be visually underwhelming, it will nonetheless be a treasure trove of new science. “We shouldn’t be scared of the K-word,” he said.
Like Kohoutek (orbit shown here), comet ISON is a first-time Oort cloud visitor. What’s more, ISON will pass much closer to the sun that Kohoutek did and so astronomers may be able to see its layers chemically come apart like peeling open an onion. Unlike in 1974, today we have a powerful and diverse collection of space and ground based telescopes to following the far visitor, and the Internet to share information at the speed of light.
A comet like this only comes along once or twice a century say experts. “Sungrazing comets are common. Fresh-from-the-Oort-cloud comets are common. Comets detected more than six times farther out than the Earth’s orbit? Not so much. The combination of all three is very rare,” said comet veteran Mike A’Hearn of the University of Maryland.
At present the comet is no longer rising in intrinsic brightness and perhaps dipped in brightness a little. It could have a shallow reserve of super-volatiles ices (not water) that has been mostly exhausted, with more waiting to be uncovered by continued activity as the comet approaches the sun. As the comet is blowtorched it may simply disintegrate and never reappear after passing within a million miles of the sun in late November.
Mike Mumma of NASA’s Goddard Space Flight Center predicted that if the comet is weakly bound together, the sun’s gravity will pull it apart and cook off the volatiles before the remaining dust could re-coalesce. “ISON is a great experiment to see all the factors that influence sungrazing survival,” said Matthew Knight of the Lowell Observatory.
Regardless of how the comet behaves, this is becoming sort of a Woodstock of space astronomy. Unlike Kohoutek, there is an armada of spacecraft position near the sun or at other planets that will be ready to follow the comet along every step of its sunward plunge. Add to that a powerful new generation of ground base observatories, and an army of dedicated amateur astronomers with sophisticated instruments for monitoring the comet.
The comet will be dissected across the electromagnetic spectrum, from radio to X-rays. “There’s a lot of potential in studying ISON, said Karen Meech of the Institute for Astronomy in Hawaii. “We’ll have a huge amount of data to learn from.”
Three NASA solar observing spacecraft will keep a keen eye on ISON as it gets so near to the sun the it will be lost from view from Earth, and actually pass through the chromosphere. (This plot shows the comet’s position starting at 1 a.m. EST on Nov. 26, 2013, and ending at 7 p.m. EST on Nov. 29, at 1 hour increments.) “It’s sort of a free solar probe, except it’s a solar probe that can fly through a domain where no man-made probe could ever go,” said Karel Schrijver of the Lockheed-Martin Corp.
The workshop astronomers agree that ISON will be an extraordinary, cliffhanger of an event. “No comet has ever disappointed me, a lot of comets have surprised me,” said A’Hearn. “When given a lemon, we make lemonade.”
Image Credit: NASA