Like Icarus, comet ISON appears to have flown too close to the sun and broken up in its corona.
Scientists had hoped that the comet from the farthest reaches of the solar system would be able to slingshot around the sun Thursday and emerge streaming a tail visible to the naked eye next month.
But after NASA telescopes tracked the comet plunging into the sun's corona, no evidence of it emerged on the other side. Scientists said they would continue to analyze imagery from the telescopes for signs of the comet or debris from it breaking up.
"At this point, I do suspect that the comet has broken up and died," says Karl Battams, a comet scientist for the Naval Research Laboratory, who joined a NASA and Google+ chat from Kitt Peak Observatory in Arizona. "Let's at least give it a couple of more hours before we start writing the obituary."
Even if the comet broke up, it offered a very rare opportunity to see how one of the oldest objects in the solar system interacted with the sun's magnetic field.
The comet originated in the Oort Cloud, a region halfway from the sun to the next closest star. Scientists say comet ISON would have been nudged by gravity from other stars into its 5-million-year plunge toward the sun.
Although scientists have tracked other comets from the Oort Cloud, Battams said this one was the first in recorded astronomy from so far away that passed so close to the sun, passing the sun at a distance of about 1 million miles.
"This is a spectacularly rare event," Battams said. "We have no idea when we're going to see something this amazing again."
The reason scientists study comets is to find out what they contain because they were born along with the solar system 4.5 billion years ago. When comets pass close enough to the sun, their ice melts away and dust gives off signals that describe its composition.
Even if comet ISON evaporated and broke apart near the sun, its behavior in the sun's magnetic field will help scientists understand more about both comets and the sun.
"This gives us an opportunity to see and study these magnetic fields in a way we normally couldn't do," said Alex Young, a solar physicist at NASA's Goddard Space Flight Center. "Nature is giving us this unique opportunity to study these magnetic fields."
ISON (pronounced ICE-on) stands for International Scientific Optical Network. It was discovered in September 2012 by a pair of amateur astronomers in Russia.
Two NASA telescopes that tracked the comet's approach to the sun were called SOHO, for Solar and Heliospheric Observatory, and SDO, the Solar Dynamics Observatory.
SOHO has a metal coin that blocks out the sun's direct light, so that the corona of fountains of magnetic field can be seen splashing off the sun. Comet ISON was visible in SOHO's red-and-blue images as it approached the sun with a long tail.
But as it approached its closest point to the sun at 1:48 p.m. ET, the half-mile point of the comet faded and the tail thousands of miles across became fuzzier. That suggested it might have broken up.
"We're not really seeing the head of the comet," Phil Plait, an astronomer and author who writes for Slate's Bad Astronomy blog, said of a SOHO image taken at 12:24 p.m. "That to me looks like the nucleus broke up."
SDO, which showed the sun in ultraviolet light as a smoldering yellow marble, glimpsed comet ISON racing toward the sun. But as SDO shifted to watch the comet reappear on the other side, ISON never showed.
This was puzzling because Dean Pesnell, a solar physicist and project scientist for SDO, said even if the comet broke up, its remains should have been visible in the magnetic field for 45 minutes.
"I'd like to know what happened to our half-mile of material that was going around the sun," Pesnell said of the comet. "We should be able to see something."
Scientists said they would continue to review images from 11 telescopes worldwide that tracked the comet, to learn what became of it and learn more about the sun.
"I'm not very hopeful at this point," Plait said of comet ISON.
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