You have to check this out!
During the last few days, observers worldwide have noticed a noticeable upturn in the overall brightness of Comet ISON as well as a lengthening of its tail. While Comet ISON has remained somewhat dark since coming back into view for skywatchers, the comet might now be on track for a brilliant show when it makes it close pass with the sun at the end of November.
One interesting but little discussed factor highlighted in today’s press release was the retrograde versus prograde rotation of the cometary nucleus. A fast, prograde spin of an elongated nucleus may spell doom for ISON, as tidal forces will rip it apart. A retrograde rotator, however, is very likely to survive the encounter.
Thus far, there are no solid indications that ISON is indeed a retrograde rotator, although there are tantalizing hints that beg for further observations.
Li notes that it’s tough to infer a bias for comets like ISON to be retrograde over prograde rotators, as we’ve only got five historical comets to go by similar to ISON, and the breakdown is thus about 50/50 for and against.
This is great and fun to play with!
The first close-up of ISON will come on 1 October, when it flies within 10 million kilometres of the Red Planet. “Mars has the best seat in the solar system,” says Carey Lisse of the Johns Hopkins University Applied Physics Laboratory. The HiRISE telescope on NASAs Mars Reconnaissance Orbiter will snap sharp pictures on a par with Hubbles images. The European Space Agencys Mars Express will also watch, alongside NASAs Curiosity and Opportunity rovers.
Around the same time, the first balloon mission to study a new-found comet will gaze up from Earth. The Balloon Rapid Response for ISON mission will launch from New Mexico in late September to measure water vapour and carbon dioxide emitted from the comet. “No other spacecraft can make these measurements,” says Andy Cheng, also at the Johns Hopkins University Applied Physics Lab.
The Messenger spacecraft will spectate from its orbit around Mercury in October, and a suite of solar space-telescopes will track the comets passage closest to the sun on 28 November. Hubble and large ground-based telescopes will observe when the comet is further from the sun.
Unfortunately, NASAs Deep Impact wont join in the festivities. The craft, which made a close-up investigation of comet Tempel 1 in 2005, made early observations of ISON in 2012. Last month, NASA lost contact with it, and they officially declared it lost today.
Given current constraints on ISON’s nucleus properties and the typically determined values for these properties among all comets, we find tidal disruption to be unlikely unless other factors (e.g., spin-up via torquing) affect ISON substantially. Whether or not disruption occurs, the largest remnant must be big enough to survive subsequent mass loss due to sublimation in order for ISON to remain a viable comet well after perihelion.
From one Internet site: “Dust from ISON will fly at the sun, activating massive solar storm activity which would in effect destroy Earth’s electric grid.” Not to be left out in the cold, remote viewers are also predicting a flyby of a “large massive Space Body” that will trigger huge solar flares.
Reality check: There is no evidence or theoretical mechanism where sun-grazing comets cause solar flares and coronal mass ejections. Though some bright comets have been seen approaching the sun immediately before flares, it is purely coincidental because comets are completely insignificant in size compared the sun.
Great article on what is needed and what to expect for viewing ISON with a backyard telescope.
“Comet ISON is paying a visit to the Red Planet,” said astronomer Carey Lisse of the Johns Hopkins University Applied Physics Lab in a NASA statement. “On October first, the comet will pass within 0.07 AU from Mars, about six times closer than it will ever come to Earth.”
AU stands for Astronomical Unit, the distance between the Earth and the sun.
Several instruments are in place to watch ISON’s Mars flyby, said NASA in the statement. Astronomers will glean information to determine the size of the comet’s nucleus and try to further refine predictions about whether it will survive its brush with the sun. The Mars Reconnaissance Orbiter is the best situated satellite for observing the comet as it cruises by the Red Planet, but a full 16 giant telescopes and satellites will be trained on the icy chunk.