Comet ISON Survived Perihelion (Grazing With The Sun) On Thanksgiving !


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Great news! We earthlings inhabiting the Northern Hemisphere might be able to get a “once in a lifetime light show” in December, compliment of Comet ISON. Comet ISON  (aka C/2012 S1. The ‘C’ means that it is a non-periodic comet, the ‘S’ means September and the ‘1″ means it was the first that discovered that month. It’s more common name (ISON) comes from the Russia-based International Scientific Optical Network which first discovered it.) passed the Sun on November 28, 2013 when it was about 1 million miles or 1.6 million km from the Sun ( in space terms, it basically means grazing the Sun) and will reach the minimum distance from Earth (64.2 million km) on Dec. 26, 2013. The European Space Agency previously declared ISON’s death on Twitter late on Thursday, but now backtracks, saying Comet ISON  “continues to surprise.”  New images of faint smudge on a screen showed a streak of light moving away from the sun that brings us a sliver of hope that Comet ISON may have survived the grazing with the sun!


STEREO-B COR2 image of c/2012 S1 or Comet ISON re-emerging about 7 hours after perihelion

“It certainly appears as if there is an object there that is emitting material,” said Alan Fitzsimmons, an astronomer at Queens University in Belfast, Northern Ireland. Comet ISON is one of the Sungrazing comets: A sungrazing comet is a comet that passes extremely close to the Sun at perihelion

Comet position of C/2012 S1 on December 11, 2013 after perihelion

– sometimes within a few thousand km (kilometers) of the Sun’s surface. While small sungrazers can be completely evaporated during such a close approach to the Sun, larger sungrazers can survive many perihelion passages. However, the strong evaporation and tidal forces they experience often lead to their fragmentation. Comet ISON is also known as  Comet Nevski–Novichonok,  a sungrazing comet discovered on September 21, 2012, by Vitali Nevski and Artyom Novichonok. The discovery was made using the 0.4-meter (16 in) reflector of the International Scientific Optical Network (ISON) nearKislovodsk, Russia. Data processing was carried out by automated asteroid-discovery program CoLiTec. Precovery images by the Mount Lemmon Survey

Comet C2012 S1 (ISON) seen from the Mount Lemmon SkyCenter on October 8, 2013, as it passes through the constellation of Leo (credit: wikimedia commons)

from December 28, 2011, and by Pan-STARRS from January 28, 2012, were quickly located. Follow-up observations were made on  September 22 by a team from Remanzacco Observatory in Italy using the iTelescope network. The discovery was announced by the Minor Planet Center on September 24. Observations by Swift in January 2013 suggested that C/2012 S1’s nucleus was around 5 kilometers (3 mi) in diameter. Later estimates were that the nucleus was only about 2 kilometers (1 mi) in diameter. C/2012 S1 was at first suspected to have disintegrated near perihelion, but CIOC members suspect a small fragment of it has survived perihelion passage because a coma has been detected.

The path of C/2012 S1 (ISON) from December 2012 through October 2013 as it passes through Gemini, Cancer, and Leo (credit: NASA's Goddard Space Flight Center/Axel Mellinger)

Comet ISON, imaged by the Hubble Space Telescope on April 10, 2013-near Jupiter's orbit; also, enhanced (coma model ratio) version (credit: NASA, ESA, and Z. Levay, ST ScI)










So, what kind of light show might we be able to expect from Comet ISON or C/2012 S1 ? Its absolute magnitude or intrinsic brightness seems to be between two previous spectacular comets: Comet C/1965 S1 (Ikeya-Seki)

Comet Ikeya-Seki (credit: Roger Lynds/NOAO/AURA/NSF)

and Comet C/2006 P1 (McNaught) .

Comet McNaught (source: wikipedia)

Both of these comets passed by the Sun very closely and were possibly the two brightest since the 1930s. Ikeya-Seki of the absolute magnitude 3.9 and McNaught 9.5 . The magnitude system is ordered such that fainter objects have higher values. It is also on a logarithmic scale, where a difference of 2.5 magnitudes corresponds to a factor of 10 in apparent brightness. A 5 magnitude difference is a factor of 100. Given the same distance from the Sun and distance from the Earth, Comet ISON would be roughly 25 times brighter than Comet McNaught and one-seventh as bright as Comet Ikeya-Seki. There may be quite an exciting show awaiting us in December of 2013!

~have a bright and sunny day~

gathered, written, and posted by sunisthefuture-Susan Sun Nunamaker
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CIOC (NASA Comet ISON Observing Campaign)

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