Swift satellite sizes up comet ISON (w/ video)

NASA's Swift sizes up comet ISON


Using images acquired over the last two months from Swift's Ultraviolet/ (UVOT), the team has made initial estimates of the 's water and dust production and used them to infer the size of its icy nucleus.


Comet ISON is now approaching the inner solar system. Discovered last year, the comet remains unusually active for its distance from the sun. If current trends continue, ISON could rank as one of the brightest comets in decades when it makes its close approach to the sun in late Nov. This animation shows the comet's approach and departure from the inner solar system from various perspectives. Credit: NASA's Goddard Space Flight Center Scientific Visualization Studio


Like all comets, ISON is a clump of mixed with dust. Often described as "," comets emit gas and dust whenever they venture near enough to the sun that the icy material transforms from a solid to gas, a process called sublimation. Jets powered by sublimating ice also release dust, which reflects sunlight and brightens the comet.

Typically, a comet's remains frozen until it comes within about three times Earth's distance to the sun. While Swift's UVOT cannot detect water directly, the molecule quickly breaks into and hydroxyl (OH) molecules when exposed to ultraviolet sunlight. The UVOT detects light emitted by hydroxyl and other important as well as sunlight reflected from dust.




NASA's Swift sizes up comet ISON
From now through Oct., comet ISON tracks through the constellations Gemini, Cancer and Leo as it falls toward the sun. Credit: NASA's Goddard Space Flight Center/Axel Mellinger














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Citation: Swift satellite sizes up comet ISON (w/ video) (2013, March 29) retrieved 17 October 2019 from https://phys.org/news/2013-03-swift-satellite-sizes-comet-ison.html

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User comments

Mar 30, 2013
"Failed to live up to expectations" Live by the solar heating model and disappointments will happen. Cathode sputtering is a more viable reality considering the jets occur before solar heating could possibly happen. The jets also appear on the dark side of the nucleus. Half of the comets we have checked out did not look like they had any water on them.

Mar 30, 2013
On a lark, I just looked up Cathode Sputtering. I suspect that it has as much to do with comet dynamics as whether a groundhog sees its shadow, or the proportion of cars with fueling ports on the left side vs. the right side. :)

Apr 01, 2013

There wouldn't be any liquid water on the surface. The water sublimates directly from solid to gas and leaves the surface as a free molecule before it has time to return any heat to the surface of the comet. The interior of the comet is near absolute zero, even near the surface.

Contrary to popular belief, most meteors that land in one piece are cold when they hit. The part that heats up and sublimates peels off so fast that the inside doesn't have time to heat up in the few seconds it takes for entry into the atmosphere.

I'm not aware of any direct observations, but if such a meteorite happened to contain any carbon ice, it should appear to smoke after landing, as the dry ice sublimates.
