Continuing a history of surprising behavior, material from Comet ISON appeared on the other side of the sun on the evening on Nov. 28, 2013, despite not having been seen in observations during its closest approach to the sun.
As ISON appeared to dim and fizzle in several observatories and later could not be seen at all by NASA’s Solar Dynamics Observatory or by ground based solar observatories, many scientists believed it had disintegrated completely. However, a streak of bright material streaming away from the sun appeared in the European Space Agency and NASA’s Solar and Heliospheric Observatory later in the evening. The question remains whether it is merely debris from the comet, or if some portion of the comet’s nucleus survived, but late-night analysis from scientists with NASA’s Comet ISON Observing Campaign suggest that there is at least a small nucleus intact.
This movie shows Comet ISON orbiting around the sun – represented by the white circle — on Nov. 28, 2013. ISON looks smaller as it streams away, but scientists believe its nucleus may still be intact. The video covers Nov. 27, 2013, 3:30 p.m. EST to Nov. 29, 2013, 8:30 a.m. EST.
Image Credit: ESA/NASA/SOHO/Jhelioviewer
Another view from SOHO’s C2 chronograph shows Comet ISON appearing bright as it streams toward the sun (right). it can be seen as a dim streak heading upward and out in the left image. The comet may still be intact.
Image Credit: ESA/NASA/SOHO/Jhelioviewer
Throughout the year that researchers have watched Comet ISON – and especially during its final approach to the sun – the comet brightened and dimmed in unexpected ways. Such brightness changes usually occur in response to material boiling off the comet, and different material will do so at different temperatures thus providing clues as to what the comet is made of. Analyzing this pattern will help scientists understand the composition of ISON, which contains material assembled during the very formation of the solar system some 4.5 billion years ago.
The days of perihelion
Nov. 28, 2013
Comet ISON went around the sun on Nov. 28, 2013. Several solar observatories watched the comet throughout this closest approach to the sun, known as perihelion. While the fate of the comet is not yet established, it is likely that it did not survive the trip. The comet grew faint while within both the view of NASA’s Solar Terrestrial Relations Observatory, and the joint European Space Agency and NASA’s Solar and Heliospheric Observatory. The comet was not visible at all in NASA’s Solar Dynamics Observatory.
“We didn’t see Comet ISON in SDO,” said Dean Pesnell, project scientist for SDO.
“So we think it must have broken up and evaporated before it reached perihelion.”
While this means that Comet ISON will not be visible in the night sky in December, the wealth of observations gathered of the comet over the last year will provide great research opportunities for some time. One important question will simply be to figure out why it is no longer visible.
Nov. 27, 2013
As Comet ISON heads toward its closest approach to the sun — known as perihelion — on Nov. 28, 2013, scientists have been watching through many observatories to see if the comet has already broken up under the intense heat and gravitational forces of the sun. The comet is too far away to discern how many pieces it is in, so instead researchers carefully measure how bright it is, which can be used to infer its current state. Less light can sometimes mean that more of the material has boiled off and disappeared, perhaps pointing to a disintegrated comet. But also a disintegrating comet sometimes gives off more light, at least temporarily, so researchers look at the comet’s pattern of behavior over the previous few days to work out what it may be doing.
Has Comet ISON broken up? It is still unclear.
At times observations have suggested ISON was getting dimmer and might already be in pieces. However, over Nov. 26-27, 2013, the comet once again brightened. In the early hours of Nov. 27, the comet appeared in the view of the European Space Agency/NASA mission the Solar and Heliospheric Observatory in the Large Angle and Spectrometric Coronagraph instrument. Coronagraphs block out the bright light of the sun in order to better see the dimmer solar atmosphere, the corona. In these images, the comet looks quite bright as it moves in from the lower right of the image. A giant cloud of solar material, called a coronal mass ejection or CME, is also seen in the images bursting off the bottom of the sun and heading out into space. It is as yet unclear if the CME is heading towards ISON but even if it does, it poses no real danger to the comet.
If the comet has already broken up, it should disintegrate completely as it makes its slingshot around the sun. This would provide a great opportunity for scientists to see the insides of the comet, and better understand its composition — as such information holds clues about what material was present during the solar system’s formation when this comet was born. However, it would likely mean no comet visible in the night sky in December. We’ll only know for sure after the comet rounds the sun on Thanksgiving Day.
Nov. 26, 2013
NASA’s Solar Terrestrial Relations Observatory, or STEREO, is monitoring Comet ISON as it approaches the sun. The latest movie from the STEREO-A spacecraft’s Heliospheric Imager shows the comet moving in from the left side over a two-day period from Nov. 20 to Nov. 22, 2013. In addition to Earth and Mercury, Comet Encke can also be seen moving through the middle of the view. The sun sits outside the field of view of this camera, located to the right, off-screen, hinted at by the steady stream of particles, called the solar wind, moving in from the right.
Comet ISON – Dazzle or Dust ?
Nov. 25, 2013
Don Yeomans, a senior research scientist at JPL, keeps a watchful eye on near-Earth objects — asteroids, comets and other space rocks. Yeomans heads a group charged by NASA to watch for objects whose orbits bring them close to Earth.
Below is a comet ISON Q&A with Don Yeomans, manager of NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory, Pasadena, Calif.
What is so interesting about comet ISON?
There’s great interest in comet ISON for a couple of reasons. First of all, it’s coming from the very edge of our solar system so it stills retains the primordial ices from which it formed four-and-a-half billion years ago. It’s been traveling from the outer edge of the solar system for about five-and-a-half million years to reach us in the inner solar system, and it’s going to make an extremely close approach to the sun and hence could become very bright and possibly a very easy naked-eye object in early December.
What will happen to comet ISON on Thanksgiving?
So there are three possibilities when this comet rounds the sun on Thanksgiving Day 2013 [Nov. 28]. It could be tough enough to survive the passage of the sun and be a fairly bright naked-eye object in the early morning sky in the first week of December. Or, the sun could actually pull it apart. The tidal forces could actually pull this comet apart and so it becomes several chunks rounding the sun and putting on a great show again in early December. Or, if the comet is very weak, it could break up into a cloud of dust and be a complete bust in December.
Do comets like ISON present a scientific opportunity?
There is going to be a small army of amateur and professional astronomers on the Earth, and spacecraft are going to be observing this object near the sun. So we’re going to find out a great deal about what this comet is made of, and hence we are going to find out a great deal about what the solar system was like four-and-a-half billion years ago.
A comet’s journey through the solar system is perilous and violent. A giant ejection of solar material from the sun could rip its tail off. Before it reaches Mars — at some 230 million miles away from the sun — the radiation of the sun begins to boil its water, the first step toward breaking apart. And, if it survives all this, the intense radiation and pressure as it flies near the surface of the sun could destroy it altogether.
Right now, Comet ISON is making that journey. It began its trip from the Oort cloud region of our solar system and is now travelling toward the sun. The comet will reach its closest approach to the sun on Thanksgiving Day — Nov. 28, 2013 — skimming just 730,000 miles above the sun’s surface. If it comes around the sun without breaking up, the comet will be visible in the Northern Hemisphere with the naked eye, and from what we see now, ISON is predicted to be a particularly bright and beautiful comet.
Cataloged as C/2012 S1, Comet ISON was first spotted 585 million miles away in September 2012.C/2012 S1, also known as Comet ISON or Comet Nevski–Novichonok, is a sungrazing comet discovered on 21 September 2012 by Vitali Nevski (Виталий Невский, Vitebsk, Belarus) and Artyom Novichonok (Артём Новичонок, Kondopoga, Russia). The discovery was made using the 0.4-meter (16 in) reflector of the International Scientific Optical Network (ISON) near Kislovodsk, Russia. This is its very first trip around the sun, which means it is still made of pristine matter from the earliest days of the solar system’s formation, its top layers never having been lost by a trip near the sun. Scientists will point as many ground-based observatories as they can and at least 15 space-based assets towards the comet along the way, in order to learn more about this time capsule from when the solar system first formed.
Even if the comet does not survive, tracking its journey will help scientists understand what the comet is made of, how it reacts to its environment, and what this explains about the origins of the solar system. Closer to the sun, watching how the comet and its tail interact with the vast solar atmosphere can teach scientists more about the sun itself.
History and Future
|Date||Comet ISON Journey|
|At least a million years ago||The comet began its journey from the Oort cloud, a swath of icy objects that orbit far beyond Neptune. This is Comet ISON’s first trip through the inner solar system.|
|September 2012||Comet ISON was first discovered by Russian astronomers, Vitali Nevski and Artyom Novichonok, using the International Scientific Optical Network in Kislovodsk, Russia.|
|Jan. 17–18, 2013||NASA’s Deep Impact acquired images of Comet ISON. The observations were unable to detect whether carbon monoxide or carbon dioxide was present.|
|January-March 2013||For two months, NASA’s Swift mission observed ISON when it was around 460 million miles away from the sun. (http://1.usa.gov/13E3yg0) Observations showed that ISON was shedding about 112,000 pounds of dust and 130 pounds of water every minute. The lower amount of water represents the fact that the comet was too far away from the sun for its water ice to have begun evaporating. Instead, other materials such as carbon dioxide or carbon monoxide ice were boiling off.|
|April-May 2013||NASA’s Hubble Space Telescope observed Comet ISON at 386 million miles away from the sun on April 10, 2013. (http://1.usa.gov/ZGGitt) Preliminary Hubble observations provided surprising results: The nucleus of the comet appeared to be no larger than 3 to 4 miles across. Since the comet was so bright and so active, scientists had assumed the nucleus was larger. Hubble found the dusty coma, or head of the comet, to be around 3,100 miles across and the tail to be more than 57,000 miles long. HST also observed the comet on May 2 and May 7, and produced an upper limit on how fast the comet was producing carbon monoxide. Hubble also released a movie of the comet from May 8, 2013:http://1.usa.gov/17RuUS1|
|June 13, 2013||NASA’s Spitzer Space Telescope observed Comet ISON at 310 million miles away from the Sun. The data are still being processed and no results have been announced yet.|
|July-August 2013||Sometime in late July or early August, the comet will pass what’s called the frost line, some 230 to 280 million miles away from the sun, when it will feel enough radiation from the sun that water will begin to evaporate and the comet will appear brighter. Some comets have broken up upon crossing the frost line.|
|August-November 2013||Beginning in August, astronomers will be able to observe the comet through ground-based telescopes once again.From early June through late-August, ISON was almost directly behind the sun as viewed from Earth, and thus could not be observed from the ground.|
|September 2013||In September, the comet will be visible near dawn in the Southern Hemisphere with binoculars.|
|Sept. 17-Oct. 15, 2013||Launch window for the Balloon Rapid Response for ISON, or BRRISON. This balloon, which with its payload will be 671 feet tall, taller than the Washington Monument, will launch from NASA’s Scientific Balloon Flight Facility in Fort Sumner, N.M. for a single day, carrying a 2.6-foot telescope and other science equipment. It will soar up to 23 miles above Earth’s surface, where it can observe the comet largely unhindered by Earth’s atmosphere.BRRISON will observe ISON in the near-infrared, near-ultraviolet and visible wavelength ranges, and will measure the ratio of carbon dioxide to water emissions from the comet. This ratio will be a vital diagnostic of the comet’s origins. These emissions are blocked by Earth’s atmosphere and cannot be measured from the ground.BRRISON is an unprecedented quick-reaction project to take advantage of the opportunity presented by the discovery of comet ISON, and is the first NASA Planetary Science Division balloon mission to observe a comet.|
|October 2013||Mars Curiosity and Opportunity will have a view of ISON in October, with Oct. 1, 2013, being the comet’s closest approach to Mars.Comet ISON will be close enough to the sun, as of Oct. 10 that it will be visible by an instrument with an extremely wide view on one of the solar observatories: the HI 2 instrument on one of NASA’s Solar Terrestrial Relations Observatories, STEREO-A. At that point the comet will be around 94.5 million miles away from the sun.Additional Hubble observations are planned to provide new estimates on nucleus size and composition as well as to search for any fragments that have broken off.|
|November 2013||Observations of Comet ISON with NASA’s Chandra X-ray Observatory will be used to study particles streaming away from the sun in the solar wind. These particles from the sun interact with Comet ISON to generate X-rays that are detected by Chandra. The first of two sets of observations is planned for early November, when Comet ISON will be passing through the hot wind produced by regions along the sun’s equator.|
|Nov. 16-19 & 21-26, 2013||Comet ISON will be visible to MESSENGER, which is near Mercury. The closest approach will be on Nov. 19.Once the comet passes Mercury, it will be on the most perilous part of its journey. The intense radiation of the sun causes material to evaporate quickly off the comet. Moreover the very pressure of the solar particles on the comet can cause it to break up. A slew of space and ground-based telescopes will watch the comet as it makes its slingshot around the sun.|
|Nov. 18-24, 2013||Launch window for NASA’s FORTIS (short for Far-ultraviolet Off Rowland-Circle for Imaging and Spectroscopy) sounding rocket, which will measure ultraviolet light from Comet ISON as it nears the sun. Such light can help scientists determine the production rate of volatile chemicals leaving the comet surface and also can be used to search for previously undetected types of atoms or molecules on the comet.|
|Nov. 21-30, 2013||As of Nov. 21, Comet ISON will begin to enter the fields of view of NASA’s space-based solar observatories. Comet ISON will be viewed first in what’s called coronagraphs, images that block the brighter view of the sun itself in order to focus on the solar atmosphere, the corona. Such images – from STEREO and the joint European Space Agency/NASA Solar Heliospheric Observatory, or SOHO — will likely be quite visually compelling. NASA’s Solar Dynamics Observatory, or SDO, will view the comet for a few hours around perihelion. SDO’s imagery should be detailed enough to gather information about how the comet evolves through the radiation and pressure of the sun’s atmosphere.All of these observatories will have different views. STEREO-A will be the only one that sees the comet transit across the face of the sun. In SDO’s view, the comet will appear to travel above the sun.The exact dates of view for these observatories is as follows:|
In addition, ground-based solar telescopes – observing in optical, infrared and radio wavelengths – will all be able to observe the comet during perihelion. Such observations will provide additional information about the composition of the comet and how material evaporates off it, fueling the dusty cloud that surrounds the nucleus.
One last solar effect could impact the comet at this stage in its journey. If the sun coincidentally sends out a giant cloud of solar particles, known as a coronal mass ejection, at the right time and direction to pass the comet, it could pull the comet’s tail right off.
|December 2013 – January 2014||If Comet ISON survives its trip around the sun, there’s a good chance that it will be incredibly bright and easily visible with the naked eye in the Northern Hemisphere. In early December, it will be seen in the morning, low on the horizon to the east-southeast. In late December and early January, it will be visible all night long.A second set of Chandra observations is planned for the middle of December to early January, when ISON will be passing through a transition region in the solar wind, where the hot wind from the Sun’s sun’s equator is mixed with a cooler wind produced by regions near the poles of the sun.|
|December 26, 2013||Closest approach to Earth will be approximately 40 million miles.|
Comet ISON and Crop Circles
Did you know……there’s been multiple crop circles depicting ISON and it’s journey around the Sun? Check these out from a few years back, and a couple of added surprises. Will ISON be a “big deal”, a cool light show, a prophecy, or an omen? I guess we will see soon enough. Either way, “they” told us this was coming.
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