NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
The Hubble Space Telescope imaged the incoming Comet ISON on Oct. 9 to find the nucleus is likely intact.
Image credit: Hamant Kumar
When Comets Break Up
Nov. 16, 2012 --
Breaking up is hard to do. Unless you are a comet. I'd like to highlight some fantastic astrophotography captured over the last month as Comet Hergenrother began to split apart, break up, and go into outburst. This first image is by Hamant Kumar. His very first comet picture! Also, check out his neat animated GIF.
Image credit: Mike Phillips
Comets appear like interlopers in the night sky. For thousands of years, people thought they were harbingers of doom and unholy signs. Even into the 20th century, when it became known that comets were chunks of ice and rock visiting the inner solar system from the colder regions of the solar system, people panicked over the imagined threat of cyanide poisoning from the tail of Halley's Comet. But unless one smacks into our planet, doomsday-style, we can safely enjoy the spectacle. This view of Comet Hergenrother was imaged by Mike Phillips.
Image credit: Paul Stewart
Photographing a comet is an exciting opportunity for astronomers to capture a current astronomical event, as for the most part the night sky doesn't change all that much. Comet hunters watch the often unpredictable objects to see how they change as they get nearer to the sun. The sun's radiation causes some of the comet's frozen material to sublimate, or turn from a solid to a gas, creating the spectacular tails. This photo is by Paul Stewart, just barely over the rooftops.
Image credit: Stuart Forman
You can actually make an analog comet of your own with a bit of dirt, water, and dry ice, or frozen carbon dioxide. Just be careful and wear safety gloves! With a bit of organic substances (like soda) and ammonia (like in window cleaner) you have a pretty good educational analog that also sublimates and makes a "tail" when you run around with it. This view was captured by Stuart Forman on October 20th with 3 x 5 min subs with Canon T1i at ISO 400 stacked with DSS with dark calibration, minor levels/curves in Photoshop, noise reduction using Colormancer noise reduction PS free plug in.
Image credit: Howard Maculsay
Sometimes, the sublimation goes too far, and the nucleus can break into smaller pieces, as Comet Hergenrother did on October 26th. The Gemini Telescope caught a tiny piece pulling away and creating its own tail. They are quick to note, however, that Earth is in no danger. Comet Hergenrother image captured by Howard Maculsay.
Image credit: Michael Rector
To learn more about Comet Hergenrother, you can hear all about it from Carl Hergenrother himself, discoverer of this particular snowball! And to see real-time images by these astronomers, do check out the weekly Virtual Star Party on Google+. I'll be the first to admit that I'm rubbish at handling a telescope, but these guys put on an incredible show of the night sky's treasures for anyone to enjoy. This final photo was captured by Michael Rector on Oct. 12.
MORE ARTICLES BY NICOLE GUGLIUCCI
Despite speculation to the contrary, Comet ISON is holding its own against the sun's heat, with its cometary nucleus apparently remaining as a solid mass.
New observations carried out by the Hubble Space Telescope on Oct. 9 have resolved the interplanetary traveler with a beautifully smooth coma (the dust and gas around the "head" of the comet) with a bright tail swept back.
The comet -- which was discovered in September 2012 by the International Scientific Optical Network (ISON), near Kislovodsk, Russia -- is believed to be a pristine cometary nucleus that has fallen from the hypothetical Oort Cloud -- a reservoir of icy fragments left over from the birth of the solar system. It is reckoned that this "shell" of proto-comets is located around 1 light-year away from the sun.
As this is its first visit to the inner solar system, astronomers theorized that ISON's nucleus might fragment as it becomes heated by the sun's energy. Looking at this image, there appears to be no abnormalities in the comet's coma that would reveal fragmentation.
Interestingly, as noted by a Space Telescope Science Institute news release, a polar jet of dust projecting from ISON's nucleus seen in Hubble images taken in April is no longer visible and likely turned off.
ISON is due to make its closest pass to the sun on Nov. 28 and, should it survive the fiery encounter, the comet could become an impressive sight in nighttime and daytime skies when it makes closest approach with the Earth on Dec. 26.