San Francisco – After a year of observations, scientists waited with bated breath on Nov. 28, 2013, as Comet ISON made its closest approach to the sun, known as perihelion. Would the comet disintegrate in the fierce heat and gravity of the sun? Or survive intact to appear as a bright comet in the pre-dawn sky?
Some remnant of ISON did indeed make it around the sun, 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.
Video follows:
On Dec. 10, 2013, researchers presented science results from the comet’s last days at the 2013 Fall American Geophysical Union meeting in San Francisco, Calif. They described how this unique comet lost mass in advance of reaching perihelion and most likely broke up during its closest approach, as well, as summarized what this means for determining what the comet was made of.
“The comet’s story begins with the very formation of the solar system,” said Karl Battams, an astrophysicist at the Naval Research Lab in Washington, D.C. “The dirty snowball that we came to call Comet ISON was created at the same time as the planets.”
ISON circled the solar system in the Oort cloud, more than 4.5 trillion miles away from the sun. At some point a few million years ago, something occurred – perhaps the passage of a nearby star – to knock ISON out of its orbit and send it hurtling along a path for its first trip into the inner solar system.
The comet was first spotted 585 million miles away in September 2012 by two Russian astronomers: Vitali Nevski and Artyom Novichonok. The comet was named after the project that discovered it, the International Scientific Optical Network, or ISON, and given an official designation of C/2012 S1 (ISON). When comet scientists mapped out Comet ISON’s orbit they learned that the comet would swing within 1.1 million miles of the sun’s surface, making it what’s known as a sungrazing comet, providing opportunities to study this pristine bit of the early solar system as it lost material while approaching the higher temperatures of the sun. With this knowledge, an international campaign to observe the comet was born. The number of space-based, ground-based, and amateur observations was unprecedented, including 12 NASA space-based assets observing Comet ISON over the past year.
Near the beginning of October, 2013, two months before perihelion, NASA’s Mars Reconnaissance Observer, or MRO, turned its HiRISE instrument to view the comet during its closest approach to Mars in October 2013.
“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, in Tucson.
In other words, Comet ISON might have been the length of five or six football fields. This small size was near the borderline of how big ISON needed to be to survive its trip around the sun.
During that trip around the sun, Geraint Jones, a comet scientist at University College London’s Mullard Space Science Laboratory in the UK studied the comet’s dust tails to better understand what happened as it rounded the sun. By fitting models of the dust tail to the actual observations from NASA’s Solar Terrestrial Observatory, or STEREO, and the joint European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, Jones showed that very little dust was produced after perihelion, which may suggest that the comet’s nucleus had already broken up by that time.
While the comet was visible in STEREO and SOHO images going into perihelion, it was not visible in the data from NASA’s Solar Dynamics Observatory, or SDO, or from ground based solar observatories during its closest approach to the sun. Dean Pesnell, project scientist for SDO at NASA’s Goddard Space Flight Center in Greenbelt, Md., explained why Comet ISON wasn’t visible in SDO and what could be learned from that: SDO is tuned to see wavelengths of light that would indicate the presence of oxygen, which is very common in comets.
“The fact that ISON did not show oxygen despite how close it came to the sun provides information about how high was the evaporation temperature of ISON’s material,” said Pesnell. “This limits what it could have been made of.”
When Comet ISON was first spotted in September 2012, it was relatively bright for a comet at such a great distance from the sun. Consequently, many people had high hopes it would provide a beautiful light show visible in the night sky throughout December 2013. That potential ended when Comet ISON disrupted during perihelion. However, the legacy of the comet will go on for years as scientists analyze the tremendous data set collected during ISON’s journey.
At 2:54 in this video;
“2009 is the first year of global governance with the G20 in the middle of the financial crisis. The Climate conference in Copenhagen is another step toward the global management of our planet.”
Herman Van Rompuy is the first full-time President of the European Council.
How’s that NWO thing working out for you Herman?
Did we ever find out who the Climategate whistleblower was?
This describes James Hansen’s last 60 hrs and last 40 years of his career! How could anyone like him give a legitimate lecture on the “Frontier of Geophysics” when his life’s work demonstrates a profound misunderstanding of anything regarding geophysics or anything about science even in the most dumbfounded of ways!
Can’t blame it on Vietnam and Agent Orange Jimmy Boy.
Ha
ISON is just one in a long series of comets heralded as the one of the century but which turn out a damp squib, comet Kohoutek being the archetypical example. Discovered at great distance and then “predicted” an eye-watering brightness at perihelium. These predictions are usually made using a rule derived from the brightness development of other comets, Halley for instance. What is then forgotten is that the behaviour of recurrent comets, which have gone through several perihelion passages and therefore gone through the cycle of outgassing and refreezing several times, can be completely different from that of sporadic comets who are first timers. For a start, most comets we know the orbit of are periodic ones and have already been selected for surviving the first passage, which strongly biases their characteristics. Most newcomers simply perish and ISON will not have been the last one.
[Snip. URL removed. You cannot come into Anthony’s home on the internet and insult and attack him. Get rid of the URL or go away. — mod.]
Hale-Bopp was the last, real, naked eye comet.
Comet Hale-Bopp in ’97 was a stunner. I’d a daily 20 mile pre-dawn drive along motorway headed north-west and just about for an entire month the skies were clear, affording spectacular views. These things can really shift and sure enough, it did vamoos. Anyone got info on its current whereabouts?
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Gunga Din says:
December 12, 2013 at 4:25 pm
I’ve only seen one comet with the my naked eye. I think it was Hyakutake in 1996.
It was bright enough that I could see it in a restaurant parking lot in the city. It looked kind of a seed from a cottonwood tree. No tail per say but an off-center fuzziness.
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When I saw Hyakutake in 1996, the nucleus was a fuzzy ball, but the faint tail stretched out an amazing distance, prb’ly 50+ deg of sky. If you looked directly at it, it was hard to see, but averted vision made it look spectacular & a quite spooky…
Eliza, I find the COLA maps this morning, including the anomaly maps. But they don’t say much about trends anyway, so not sure what purpose they would serve either side.
To u.k.(us):
Look up the term “proper motion”. This is the angular component
of velocity of a star relative to the Solar system. Adding in radial
motion (much harder to measure), it’s been estimated that the
star Wolf 424 has an actual velocity of approximately 555 kilometers
per second. This would lead to it clipping off a distance of one
light-year in a mere 540 years. Thus, over a time frame of several
millions of years, this star could cover 1000’s of light-years. Other
stars have slower motions, but it’s quite conceivable that a number
of stars could have passed relatively close to the Solar system over
that time span.
Beyond that, the mostly postulated Oort cloud is bound to the Sun
only very weakly. Even at the 1 AU of the Earth’s orbit, the acceleration
from the Sun’s gravity that holds the Earth in its orbit is only about
0.006 meters/second/second. At a distance of, say, 5200 AU, that
would be a factor of 27 million weaker, or only about
2 x 10^-10 meters/second/second. So a star of Sol’s mass passing
within 10000 AU of our postulated object 5200 AU out in the Oort
cloud would have a gravitational influence of about 1/4 as much as
Sol’s gravity–easily enough to significantly alter its orbit.
So, as incredible as it may sound, you shouldn’t have any difficulty
believing that a “passing star millions of years ago” could have
perturbed comet ISON from what would have been a peaceful
life in the Oort cloud and sent it plunging wildly inward toward
its recent close rendezvous with the Sun.
If you are fascinated by stellar distances, might want to check this out in Chrome:
http://workshop.chromeexperiments.com/stars/
boris says:
December 12, 2013 at 3:35 pm
Any rumors of rock shards of Ison heading for Earth yet?
I took a bit of interest in this back in September, using my own hand-made Newtonian simulation model, and NASA state vectors. I reckoned That, if Ison broke apart, most of the outbound debris field would pass a long way from Earth, but there was a very slim outside chance of some impacting Earth between the end of December 2013 and mid January 2014.
There have also been predictions made that on 15 Jan 2104 the Earth would pass through the debris trail left by Ison when it was inbound earlier this year. I looked at that too using my model, and didn’t think we’d be anywhere near it.
Anyway, I don’t plan on staying awake on 15 Jan 2014. Or any time over the previous two weeks.
Frank Davis,
You remind me – it’s been several years since a “The World will End on XX/YY/ZZZZ” pediction. “Where have all the prophets gone? Long time pa-a-ssing …” Too small profits for prophets?
Brians356, there are still plenty of prophecies of doom surrounding Ison.
I really think that there are people who can’t sleep at night unless they’re convinced that the world is going to end tomorrow or next week or next year.
It never, ever, ever stops.
Well, I guess I meant there has been no idiotic news fixation on some long-bearded saffron- robed figure surrounded by pretty nymphs of late. I guess the zombie idiocy is a proxy.
Brians356.. lol no they went widespread and all in on AGW hehehehehe.