Planetary Science Institute scientist Dr Jian Yang Li, has been tasked with studying Ison.
Dr Jian Yang Li who is a world leading comet expert and has worked with NASA on the Deep Impact and Dawn missions, presented his research findings which were funded by NASA and the Space Telescope Science Institute to the American Astronomical Society's division for planetary sciences 45th Annual Meeting in Denver.
Dr Jian Yang Li said:
“We measured the rotational pole of the nucleus. The pole indicates that only one side of the comet is being heated by the sun on its way in until approximately one week before it reaches it closest point to the sun,
Since the surface on the dark side of the comet should still retain a large fraction of very volatile materials, the sudden exposure to the strong sunlight when it gets closer to the sun than Mercury could trigger huge outbursts of material. We measured the color of the coma, and found that the outer part of the coma is slightly redder than the inner part, This color change is unusual in comets, and seems to imply that the inner part contains some water ice grains, which sublimate as they move away from the nucleus.”
“As a first-time visitor to the inner solar system, Comet C/ISON provides astronomers a rare opportunity to study a fresh comet preserved since the formation of the Solar System, The expected high brightness of the comet as it nears the sun allows for many important measurements that are impossible for most other fresh comets.”
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| This image shows the color change of Comet C/ISON’s dust coma. The white dot at the center of the coma marks the location of the nucleus. ISON’s dust coma appears to be less red near the nucleus than it is further away from the nucleus. Although the color change is actually very small, it could be an indication of relatively more water ice particles near the nucleus. Those icy particles evaporate, as they move outward, makes the coma appear redder. |
In a separate study by scientists at the Lowell Observatory and Southwest Research Institute (SwRI).
funded by NASA's Lunar Science Institute, carried out new numerical simulations and interpreted them using data from the historical records of Sun-grazing comet behavior.
Dr Kevin Walsh, a research scientist in SwRI's Planetary Science Directorate at Boulder, Colorado said:
"A major part of our work was to test if the encounter with the Sun would provide enough of a spin increase to pull material off the surface of the comet, When the comet passes near the Sun, it feels the tidal forces pulling on it, and it also gets a slight spin increase due to this rapid flyby. This spin increase is in the prograde direction, so if the comet is already spinning prograde, then it's just that much closer to spinning fast enough to lose mass.A non-spinning or retrograde (back-spinning) comet is more likely to survive because the "backspin" cancels out some of the tidal forces nearest the Sun. The opposite effect would be seen if the comet were spinning prograde, similar to a tennis ball with topspin. In that case, the spin direction would increase the tidal forces at the surface nearest the Sun and aggravate the disruptive potential, even for a comet of far greater density. The faster the prograde rotation and the lower its density, the greater the chances of a comet's disruption."
There has been a lot of speculation of late that Ison will not be as bright as previously thought. This research by the Planetary Science Institute shows that as Ison is not spinning as fast as we would normally expect a comet too. This means that some where in the region of half the ice and gasses that make up the tail are still locked up and waiting to be set free. It is these gases that make up the comets tail and coma. The study by the Lowell Observatory and Southwest Research Institute has given us new hope that Ison WILL survive its encounter with the sun and backs up the finds by the PSI. All in all today has been full of great news of astronomers across the world!
