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Comet ISON (formal scientific designation; Comet C/2012 S1) is making its first approach to the inner Solar System
and is known as a sungrazing comet.
Key Dates Comet ISON – C2012 S1
21 September 2012: Discovered
01 October 2013: Closest Approach to Mars
28 November 2013: Closest Approach to the Sun - Perihelion at 18:37 UTC/GMT
26 December 2013: Closest Approach to Earth (If it survives solar perihelion encounter)
In Brief about Comet ISON - C2012 S1
Comet ISON is making its first approach to the inner Solar System
Comet ISON (or Comet C/2012 S1) is making its first approach to the inner Solar System and is known as a sungrazing comet. It passed Mars on 01st October 2013 and reaches perihelion (closest approach) with the Sun on 28 November 2013.
Comet ISON will pass closest to Earth during December 2013
Assuming it survives its perihelion encounter with the Sun, Comet ISON will pass closest to Earth on 26th December 2013 at a distance of 39.9 million miles/64.2 million km (or about 167 times farther away than the Moon) and continue on its journey towards the outer Solar System.
ISON - C2012 S1 is a Sungrazing Comet
ISON – C2012 S1 is a sungrazer comet. Most sungrazer comets follow a similar orbit called the Kreutz Path - belonging to the same family - called the Kreutz Group. Although ISON is a sungrazing comet, it is not in the Kreutz Group of Comets.
ISON’s Acceleration and Momentum
Early calculations suggests that ISON’s – C2012 S1 encounter with the Sun, may propel and greatly accelerate the comet with enough momentum to escape the solar system entirely, never to return. It would seem that this is a once only event and this is the only time we will ever see ISON.
ISON 0 C/2012-S1 Speed
ISON’s average speed during October was 81.725mph/131,523 kph. The comet will continue to accelerate towards the gravitational pull of the Sun until 28th November 2013 when ISON will reach a whopping speed of approximately 845,000 mph/1,359,895 kph.
Discovered by Vitali Nevski from Belarus, and Artyom Novichonok from Russia.
Discovered by Vitali Nevski (Виталий Невский) from Belarus, and Artyom Novichonok (Артём Новичонок) from Russia.
Discovery made by using the 0.4-meter (16 in) reflector ISON network
Discovery made by using the 0.4-meter (16 in) reflector of the International Scientific Optical Network (ISON) near Kislovodsk, Russia, and using the automated asteroid-discovery program CoLiTec.
Images of Comet ISON - C/2012 S1 were taken by NASA's Spitzer Space Telescope
These images of Comet ISON - C/2012 S1 were taken by NASA's Spitzer Space Telescope on 13 June when ISON was approximately 310 million miles/500 million km from the sun. The photographs of ISON were taken with Spitzer Space Telescope Infrared Array Camera using two different near-infrared wavelengths at 3.6 and 4.5 microns – these colours were used to enhance the clarity of ISON - C/2012 S1.
The left image shows a 3.6-micron photograph of the fine tail of rocky dust, emanating from the comet. The tail is being blown back by the pressure of the solar-wind as ISON is pulled by gravity towards the Sun.
The 4.5 micron image on the right is ISON with the dust removed revealing a spherical structure and the first detection of a neutral gas atmosphere surrounding ISON. It is probably carbon dioxide dissipating from the surface of the comet at an estimated 2.2 million pounds/1 million kilograms a day.
Hubble image of ISON, 10 April 2013
Hubble took this image of ISON on 10 April 2013, using its HST Wide field Camera 3/UVIS F606W V, when the comet was just inside the orbit of Jupiter at a distance of 394 million miles/634 million km from Earth.
Hubble photographed ISON, 10 April 2012, when ISON was 386 million miles/621 million km from the Sun and 394 million miles/634 million km from Earth
Abobe: ISON’s coma (its dusty atmosphere) is approximately 3,100 miles/4,989 km across and its dust tail extends more than 57,000 miles/ 91,733 km. Hubble can’t detect the whole of the tail, which is beyond Hubble’s field of view at this distance.
Official International Astronomical Union name of the comet is C/2012 S1 (ISON)
Why is Comet ISON called ISON?
and why is Comet ISON also called comet C/2012 S1(ISON)?
Here's how the name C/2012 S1 (ISON) breaks down:
C indicates that ISON is not expected to return to the inner solar system. Regular orbital comets, such as Comet Halley, are designated with P for periodic comets, meaning its orbital period is less than 200 years.
2012 marks the year of discovery.
S designates the half month in which it was discovered. ISON was discovered in the last half of September.
1 means it was the first comet discovered in that period.
The rest of the name gives credit to the discoverer, or discoveries. For example; comet D/1993 F2 Shoemaker-Levy 9 (Shoemaker-Levy 9 was the comet that awesomely ploughed into Jupiter during 1994). It was named 9 because it was the ninth periodic comet discovered by Eugene and Carolyn Shoemaker and David Levy.
It is now common for many comets to bear names of Spacecraft and Robotic Surveys, as these are extremely effective at spotting such astronomical phenomena. That is the reason why some comets have; LINEAR, SOHO or WISE in their designations.
enhanced image of comet ISON - C2012 S1
An enhanced image of comet ISON - C2012 S1, showing the structure of the inner coma of ISON.
(The coma is the particles and gases that make a cloud around the nucleus of a comet. The coma is lit by the Sun, and sunlight also pushes this material making the bright tail of a comet.)
The photo of ISON is a computer processed image which proportionally decreases in brightness from the core of the nucleus to the outer edge of the coma. ISON's coma shows dust particles being released on ISON’s sunward-facing side of the comet's nucleus. This type of information is extremely important for determining the comet's shape, evolution, and spin of the solid nucleus.
photograph Image from Hubble WFC3/UVIS -
Image Credit: NASA, ESA, J.-Y. Li (Planetary Science Institute), and the Hubble Comet ISON Imaging Science Team
Discovered by (left) Artyom Novichonok (Артём Новичонок) from Russia and (right) Vitali Nevski (Виталий Невский) from Belarus.
ISON was Discovered on 21 September 2012
At a Distance of 584 million miles/ 939 million km (6.29 AU) from the Sun
ISON was discovered by Artyom Novichonok (Артём Новичонок) from Russia and Vitali Nevski (Виталий Невский) from Belarus on 21 September 2012 when the comet was at a distance of 584 million miles/ 939 million km (6.29 AU) from the Sun.
Novichonok (Новичонок) and Nevski (Невский)took this image of C/2012 S1 (ISON) on 21 September 2012.
This image of ISON is one of four original CCD photographs taken by Novichonok and Nevski who used four 100 second exposures using the 0.4-m f/3 Santel Reflector Telescope, near Kislovodsk, Russia, part of of the International Scientific Optical Network (ISON).
The images were loaded the images into a space program called CoLiTec, which is a computer program designed to detect comets and asteroids that have moved between the various images. A bright object with unusually slow movement was detected, which was thought could only mean that the celestial object was located beyond the orbit of Jupiter. The images showing the object were all acquired during the period of 21 September 2012.
Notification of the discovery was sent to the Central Bureau for Astronomical Telegrams, which placed the object on the NEOCP web page of the Minor Planet Center, so that other observers could obtain images. At the time it was not certain if the celestial object was a minor planet or a comet. Artyom Novichonok booked time on the 1.5-m reflector at Majdanak Observatory, Uzbekistan. Other observers following up on the NEOCP web site bulleting, had already reported the cometary appearance, and their images confirmed that Nevski and Novichonok had discovered a comet, so was this in mind the comet was named ISON, instead of being named after the discoverers Nevski, and Artyom Novichonok.
Image from the Swift Spacecraft Ultraviolet/Optical Telescope
ISON is n Middle of photograph
Photograph of Comet C/2012 S1 ISON from the Swift Spacecraft Ultraviolet/Optical Telescope taken on 30 January 2012.
Comet ISON is in the middle of the photograph, located approximately 3.3 degrees from the bright star Castor in the constellation Gemini.
The photo optical exposure time was 5.5 minutes. ISON was 460 million miles/740 million km from the Sun, and 375 million miles/604 million km from Earth.
photo Credit: NASA/Swift/D. Bodewits, UMCP
Below a video of Comet ISON and Comet Encke, from NASA's STEREO-A Spacecraft
The video of comet ISON and Comet Encke was taken by NASA Spacecraft STEREO Heliospheric Imager. It was taken over 5 days between 20 November to 25 November 2013. The Sun is out out of view to the right.
raw video credit; NRL/NASA STEREO/CIOC
Comet ISON image from NASA SOHO
16:11 UTC/GMT 28 November 2013. It is the opinion of NASA’s CIOC Team that Comet ISON is behaving like a sungrazing comet. It is not known if the nucleus is intact or not, but analyses indicate that its rate of brightening is directly in line with that of what has previously been experienced with other sungrazing comets. However, this has no inference on its chances of survival. We won’t know if ISON will survive, and we won't know until it either does survive or vaporizes. But at the moment the comet is still "alive" and brightening dramatically in accordance with the behaviour of what is expected from sungrazers.
Perihelion at 18:37 UTC/GMT
Comet ISON perihelion video 28 November 2013
Comet ISON - C2012 S1 video
Comet ISON video, describing a little about the comet in text, set to the music of Heaven and Hell, by Vangelis. You can watch in full screen by selecting the appropriate icon in the bottom right hand side of the video.
Enhanced image of Comet ISON (C2012 S1)
showing the structure of the inner coma of ISON.
Artyom Novichonok and Vitali Nevski.
Diagram of inner Solar System showing relative positions of Mercury, Venus, Earth, and Mars, in Relation to Comet C/2012 S1 (ISON)
click image to enlarge.
If ISON Breaks Up
If it does break up, the fragments will not go in all directions (for example - like an explosion on Earth).Instead the fragments will follow the path of its parent body, continuing along the same course. If it does happen, we on Earth may be treated to faint pearls of diamonds in the sky. Each fragment producing its own faint graceful tail.
Comet ISON might not Survive its Journey around the Sun
The comet may not survive its journey around the Sun but it is now bright enough to be visible through small telescopes and maybe binoculars. By late October / early November it will pass through the constellations of Leo and Virgo.
The Kreutz Path
Many sungrazer comets follow a similar orbit called the Kreutz Path - belonging to the same family - called the Kreutz Group. Although ISON is a sungrazing comet it is not in the Kreutz Group of Comets. Early calculations predict that ISON’s – C2012 S1 encounter with the Sun, may propel and greatly accelerate ISON with enough momentum to escape the solar system entirely - never to return. It would seem that this is a once only event and this is the only time we will ever see ISON.
Raw video: credit; ESA/NASA/SOHO/SDO/GSFC
Comet ISON appeared to dim and fizzle in several observatories and disappeared, and could not even be seen by NASA's Solar Dynamics Observatory or by any ground based solar observatories.
Many scientists thought that Comet ISON had disintegrated completely, however later in the evening appearing from the European Space Agency and NASA's Solar and Heliospheric Observatory, a streak of bright material was observed streaming away from the Sun.
At the moment we cannot say with absolute certainly if it is broken pieces of debris from the original comet, or if some portion of the comet's nucleus survived, but late-night analysis from scientists of NASA's Comet ISON Observing Campaign suggest that there is at least a small nucleus (of some type) intact.
In this video the bright light of the sun is blocked so that sun emitting structures are visible. The comet can be viewed in the lower right on its way towards the Sun. A giant cloud of solar material (a coronal mass ejection or CME) can be seen being ejected from the sun. Comet ISON disappears behind the Sun for a while, but an object (or objects) can be seen emerging from the other side of the Sun.
Further analyses is needed before it can be stated for absolute certainty if this is a single nucleus. At the moment it looks like there may be a small fraction of ISON intact in one piece and it is now actively releasing material, but it might be a dust-ball. But even if there is a single nucleus, it is too soon to say how long it will survive, or predict if the comet will be visible in the night sky, or predict the brightness of the comet.
Comet ISON will not be 15 times brighter than the Moon
There was a lot of exaggerated reports that ISON – C/2012 S1 will be as bright as the Moon. It will not.
Comet ISON - C/2012 S1 will not dazzle the sky.
Scientists and astronomers can not say for sure what will happen; newly discovered comets such as ISON (a sungrazing comet) are notoriously unpredictable in their behaviour, we can calculate their trajectory, and have knowledge of their composition, we know of its velocity, but coming so close to the Sun, we don’t know for sure if the comet will fragment into smaller chunks; or evaporate itself and disappear, or survive its close encounter with the Sun and continue on its orbit around the Sun, or in some cases, escape the gravitational pull of the Sun and escape our Solar System altogether.
Diameter of ISON’s nucleus
Calculations using data from NASA’s Swift satellite estimate ISON’s nucleus to be approximately 3 miles/4.828km in diameter.
C/2012 S1 (ISON) naked eye magnitude
ISON is not expected to reach naked eye magnitude until around 06th November. By the end of November its proximity to the Sun will make it difficult to observe. In early December the comet (if it survives its journey around the Sun) may be seen in the pre-dawn sky as it passes through Scorpius, Ophiuchus, Serpens, Hercules and Draco. By January 2014 it will fade again and only large telescopes will be able to view it as the comet heads away to the outer Solar System
Edge on view: Diagram of inner Solar System showing relative positions of Earth, Venus and Mercury in Relation to Comet C/2012 S1 (ISON)
click image to enlarge
mage credit: NASA/JPL-Caltech/JHUAPL/UCF
images of Comet ISON - C/2012 S1
taken by Spitzer Space Telescope
Image Credit:NASA, ESA, J.-Y. Li (Planetary Science Institute), and the Hubble Comet ISON Imaging Science Team.
Hubble photographed ISON, 10 April 2012,
when ISON was 394 million miles/634 million km from Earth.
Comet ISON was discovered by Artyom Novichonok (Артём Новичонок) from Russia and Vitali Nevski (Виталий Невский) from Belarus on 21 September 2012 when the comet was at a distance of 584 million miles/ 939 million km (6.29 AU) from the Sun.
ISON will move in the general direction of Earth and come closest on 26 December 2013
If ISON survives its swingby of the Sun, the comet will move in the general direction of Earth and come closest on 26 December 2013 at a distance of 39.9 million miles/64.2 million km, which is about 167 times farther than the distance of the Moon.
ISON’s average speed during October was 81.725mph/131,523 kph.
The comet will continue to accelerate towards the gravitational pull of the Sun until 28th November 2013 when ISON will reach a whopping speed of approximately 845,000 mph/1,359,895 kph.