Nasa has finally explained what happened to Comet ISON, the so-called 'Comet of the Century' which disappeared above the surface of the Sun.
After a 4.5 billion-year life in the Oort cloud at the edge of our solar system, and then a 3.5 million-year plunge towards the Sun, the comet came within 750,000 miles of its surface in November before coming to a tragic end.
But something did emerge from the Sun - if not the comet (as was originally hoped) then at least a piece of it. And Nasa has now told us why, and what it was.
"Some remnant of ISON did indeed make it around the sun," Nasa said. "But it quickly dimmed and fizzled as seen with NASA's solar observatories. This does not mean scientists were disappointed, however. A worldwide collaboration ensured that observatories around the globe and in space, as well as keen amateur astronomers, gathered one of the largest sets of comet observations of all time, which will provide fodder for study for years to come."
Nasa explained that the comet "lost mass in advance of reaching perihelion" and "most likely broke up during its closest approach". Why? Firstly, it just wasn't big enough.
"The size of ISON's nucleus could be a little over half a mile across --- at the most. Very likely it could have been as small as several hundred yards," said Alfred McEwen, the principal investigator for the HiRISE instrument at Arizona State University - IE "near the borderline of how big ISON needed to be to survive its trip around the sun".
But there is good news too - Nasa said that while the light show was a let-down, "the legacy of the comet will go on for years as scientists analyze the tremendous data set collected during ISON's journey".
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