by Nicole Mortillaro

December 13, 2013

from GlobalNews Website

 

In this combination of three images provided by NASA,

comet ISON appears as a white smear heading up and away from the sun

on Thursday and Friday, Nov. 28-29, 2013.
AP Photo/NASA

 

TORONTO

“Comet of the century!”

“To be seen in the daytime sky!”

These were only a few claims hyped by media upon the discovery of Comet ISON in September 2012 by Russian astronomers Vitali Nevski and Artyom Novichonok (a comet is usually named after its discoverer, but this one was named after the project that discovered it, the International Scientific Optical Network, ISON).

Of course, none of those claims were true.

But for scientists, it didn’t matter: ISON was a chance to peer back at the very beginning of our solar system (read 'UPDATE - Comet ISON lives!').

Karl Battams, astrophysicist at the United States Naval Research Laboratory (NRL) in Washington, DC, and the voice of ISON throughout the comet’s close pass, was happy with what was accomplished.

Battams led the Comet ISON Observing Campaign.

Battams stressed that scientists never claimed ISON would put on the show some believed would happen.

“Before us scientists even got to put our word in, there were stories about the thing being brighter than the full moon and ‘comet of the century,’ so that made life difficult for us because what we… had to convey was that this was a really, really exciting object, just not for the reasons that you’ve been reading about.”

VIDEO: Comet ISON’s pass around the sun (NASA)
 

And that reason was this: ISON was born out of the Oort cloud - a cloud that extends far beyond the orbit of Pluto - trillions of kilometers away from the sun and which was born 4.5 billion years ago.

And the fact that this comet was a sun-grazer - a comet that would pass very close to the sun - made it even more exciting. Scientists would be able to see how this ancient piece of rock interacted with solar radiation, learning about its composition and characteristics.

This was ISON’s first pass, which meant that it had never been bombarded by the sun’s radiation. Scientists wondered if the comet would survive such a close pass - 1.2 million kilometers - above the sun’s surface.

The sun is blazing hot at this distance, so hot that it vaporizes almost everything.

“The very hardest rock you can imagine. If the comet was coated in diamonds, the diamonds would instantly boil away and vaporize,” Battams said.

All that heat and radiation was too much for the new comet.

Battam said that it may have been nicer to have had something in the sky for people to see for themselves, but that doesn’t diminish how important a role the comet played for scientists.

“We’ve gotten to watch this thing for such a long period of time now, and we’ve recorded the largest and certainly the broadest data set about a comet in history…

 

One of the key parts of studying a comet is how were they put together. I think as any kid will tell you, the best way to find out how a toy is put together is to rip it apart,” Battams said, laughing.

 

“And as sad as it may seem, the sun ripped apart our little Christmas present to see how it was put together, and that’s what we’ve got to try to learn from.”

Astronomers will be analyzing the comet for months to come.

And they have plenty of data to use.

“Scientifically, it’s just been absolutely incredible,” he said.

 

“I think for me what I loved the most about this whole experience is that we’ve pulled together not only professional observers from big ground-based facilities, but we’ve got 13 different spacecraft involved… Even stuff from Mars.

 

And to top it all off, the amateur community has just been completely crucial to this whole process. We’ve got an army of eyes around the world.”

Various NASA observing campaigns.

(NASA)
 

Though Hubble is scheduled to image where ISON should be, Battam doubts that there will be anything to see.

Two other telescopes, Chandra - an X-ray telescope - and Spitzer - an infrared telescope - will also take a look. It’s good to do this, Battam said, just to confirm that ISON is indeed gone.

Though ISON may be gone, Battams pointed out that there’s still a comet gracing our skies, Comet Lovejoy, that people can enjoy.
 

Comet ISON may be gone,

but Comet Lovejoy (C/2013 R1) is still grazing the pre-dawn sky.

(Courtesy of Bill Longo)
 

The NRL has received many calls from people who bought telescopes in the hope of catching ISON.

Now that it’s gone, they wonder if there’s anything else to see.

“The sky is full of wonders. And the next bright comet is just around the corner,” Battams said.

Where to find Comet Lovejoy

around 5 a.m. from a latitude of 43 degrees.

(Stellarium)
 

Next year will be chock-full of even more exciting comets.

There will be Comet C/2013 A1 (Siding Spring), which will pass incredibly close to Mars at about 110,000 km above the planet’s surface (there had been talk about it colliding with Mars, but calculations have shown that this will not happen).

There is also the European Space Agency’s Rosetta mission which will release a lander on the comet 67 P/Churyumov-Gerasimenko.

“And,” Battams said, “Who knows what will turn up in the meantime.”

Battams’s busy schedule is just settling down. He’s spent months observing and analyzing ISON.

So, when asked what the next thing he’s excited about, Battams laughed and said,

“A rest.”

Fire vs. Ice

The Science of ISON at Perihelion
December 10, 2013

from NASA Website
 

After several days of continued observations, scientists continue to work

to determine and understand the fate of Comet ISON:

There's no doubt that the comet shrank in size considerably

as it rounded the sun and there's no doubt that

something made it out on the other side to shoot back into space.
Image Credit: ESA/NASA/SOHO
 

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.

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.

A white plus sign shows where the Comet should have appeared in this SDO image.

This image from NASA's Solar Dynamics Observatory

shows the sun, but no Comet ISON was seen.

A white plus sign shows where the Comet should have appeared.

Image Credit: NASA/SDO
 

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.