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".
This new view of Comet C/2012 S1 (ISON) was taken with the TRAPPIST national telescope at ESO's La Silla Observatory on the morning of Friday 15 November 2013. Comet ISON was first spotted in our skies in September 2012, and will make its closest approach to the Sun in late November 2013.
<a href="http://www.isoncampaign.org/potw-nov18" target="_blank"> Waldemar Skorupa (Kahler Asten, Germany)</a>
The view from Italy
"Taken by Kosmas Gazeas on November 18, 2013 @ University of Athens Observatory, Athens, Greece, remotely controlled from ...Netherlands!"
<a href="http://spaceweather.com/" target="_blank">Michael Jäger of Ebenwaldhöhe, Austria</a>: "Whatever exploded from the comet's core also created a spectacularly-long tail, more than 16 million kilometers from end to end."
<a href="http://www.flickr.com/photos/hiroc/10908164844/sizes/l/">Hisayoshi Kato</a>: "the comet after the outburst on November 14, 2013. North is up, and East is to the left."
This graphic shows the expected location of the comet named C/2012 S1 (ISON) on Nov. 28, 2013. In late November and December of 2013, it could put on a show when heating from the sun could stir up a great deal of icy and dusty material. The comet is not a threat to Earth. At the time of its closest approach to Earth, on Dec. 26, 2013, comet ISON will come no closer than 40 million miles. When considering Earthly endeavors, that's not exactly a ringside seat.
Comet ISON on April 10, 2013
Hubble's view of Comet ISON (C/2012 S1) on April 10, 2013. This image was taken in visible light. The blue false color was added to bring out details in the comet structure
Comet Ison Roars Through Leo
In the early morning of Oct. 25 (6:45 a.m. EDT), NASA's Marshall Space Flight Center in Huntsville, Ala., used a 14" telescope to capture this image of Comet C/2012 S1 (ISON), which is brightening as it approaches the sun. The comet shines with a faint green color just to the left of center. The diagonal streak right of center was caused by the Italian SkyMed-2 satellite passing though the field of view. At magnitude 8.5, the comet is still too faint for the unaided eye or small binoculars, but it's an easy target in a small telescope. At this time of this image, ISON was located in the constellation of Leo the Lion, some 132 million miles from Earth and heading in toward the sun at 87,900 miles per hour.
NASA’s Hubble: Galaxies, Comets, and Stars! Oh My!
Approaching the sun, Comet ISON floats against a seemingly infinite backdrop of numerous galaxies and a handful of foreground stars. The icy visitor, with its long gossamer tail, appears to be swimming like a tadpole through a deep pond of celestial wonders. In reality, the comet is much, much closer. The nearest star to the sun is over 60,000 times farther away, and the nearest large galaxy to the Milky Way is over thirty billion times more distant. These vast dimensions are lost in this deep space Hubble exposure that visually combines our view of the universe from the very nearby to the extraordinarily far away. In this composite image, background stars and galaxies were separately photographed in red and yellow-green light. Because the comet moved between exposures relative to the background objects, its appearance was blurred. The blurred comet photo was replaced with a single, black-and-white exposure. The images were taken with the Wide Field Camera 3 on April 30, 2013. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy Inc., in Washington, D.C.
NASA's Hubble Sees Comet ISON Intact
A new image of the sunward plunging comet ISON suggests that the comet is intact despite some predictions that the fragile icy nucleus might disintegrate as the sun warms it. The comet will pass closest to the sun on Nov. 28. In this NASA Hubble Space Telescope image taken on Oct. 9, the comet's solid nucleus is unresolved because it is so small. If the nucleus broke apart then Hubble would have likely seen evidence for multiple fragments. Moreover, the coma or head surrounding the comet's nucleus is symmetric and smooth. This would probably not be the case if clusters of smaller fragments were flying along. A polar jet of dust first seen in Hubble images taken in April is no longer visible and may have turned off. This color composite image was assembled using two filters. The comet's coma appears cyan, a greenish-blue color due to gas, while the tail is reddish due to dust streaming off the nucleus. The tail forms as dust particles are pushed away from the nucleus by the pressure of sunlight. The comet was inside Mars’ orbit and 177 million miles from Earth when photographed. Comet ISON is predicted to make its closest approach to Earth on Dec. 26, at a distance of 39.9 million miles.
Predicted Path for Comet ISON for Late November 2013
Predicted hour-by-hour position of Comet ISON in various instruments on one of NASA’s Solar Terrestrial Relations Observatory spacecraft between 1 a.m. EST on Nov. 26, 2013, and 7 p.m. EST on Nov. 29, 2013. The blue field of view is from the outer coronagraph, green from the inner coronagraph, and orange from the Extreme Ultraviolet Imager
Comet ISON Passes Through Virgo
Comet ISON shines in this five-minute exposure taken at NASA's Marshall Space Flight Center on Nov. 8 at 5:40 a.m. EST. The image has a field of view of roughly 1.5 degrees by 1 degree and was captured using a color CCD camera attached to a 14" telescope located at Marshall. At the time of this picture, Comet ISON was 97 million miles from Earth, heading toward a close encounter with the sun on Nov. 28. Located in the constellation of Virgo, it is now visible in a good pair of binoculars.
This photo was taken by reader Mike Davies