Jupiter's moon, Europa, appears to have clay-like minerals on it (visible in blue in the false-color patch, amid red-colored water ice). The information came from new data analysis from NASA's Galileo mission, which concluded in 2003. The backdrop is a mosaic of visual-light images from Galileo's Near-Infrared Mapping Spectrometer. Credit: NASA/JPL-Caltech/SETI
The cool thing about space missions is long after they conclude, the data can yield the most interesting information. Here’s an example: Jupiter’s moon Europa may have a ripe spot for organic materials to take root.
Scouring the data from NASA’s past Galileo mission — which ended a decade ago — scientists unveiled an area with “clay-like minerals” on it that came to be after an asteroid or comet smashed into the surface. The connection? These celestial party-crashers often carry organics with them.
“Organic materials, which are important building blocks for life, are often found in comets and primitive asteroids,” stated Jim Shirley, a research scientist at NASA’s Jet Propulsion Laboratory. “Finding the rocky residues of this comet crash on Europa’s surface may open up a new chapter in the story of the search for life on Europa.”
Reprocessed Galileo image of Europa’s frozen surface by Ted Stryk (NASA/JPL/Ted Stryk)
Europa is considered one of the best spots in our solar system to look for life, due to the ocean lurking beneath its icy surface, surface salts that can provide energy, and a source of heat as the mighty Jupiter squeezes and releases the moon like a tennis ball.
The minerals (called phyllosilicates) emerged after Shirley’s team ran a new analysis on infrared pictures snapped by Galileo in 1998, basically working to refine the signal out of the images (which are much lower quality than what we are capable of today).
After the analysis, the phyllosilicates appeared in a “broken ring”, NASA stated, about 75 miles (120 kilometers) away from a crater site. The crater itself is about 20 miles (30 kilometers) in diameter. Scientists are betting that the ring of phyllosilicates is debris (“splash back of material”, NASA says), after a celestial body struck at or around a 45 degree angle from vertical. It’s unlikely the phyllosilicates came from Europa’s ocean given the crust, which can be as thick as 60 miles (100 kilometers).
Europa Report was a 2013 film that focused on a human mission to the Jovian moon. Poster by Start Motion Pictures.
“If the body was an asteroid, it was likely about 3,600 feet (1,100 meters) in diameter. If the body was a comet, it was likely about 5,600 feet (1,700 meters) in diameter. It would have been nearly the same size as the comet ISON before it passed around the sun a few weeks ago,” NASA stated.
To be clear, nobody has found organic materials on Europa directly, and even if they were detected it would then be another feat of science to determine if they related to life or not. This does, however, lend credence to theories that life came to Earth through comets and asteroids.
Comet C/2011 W3 (Lovejoy) imaged by the Subaru Telescope on Dec. 3. Image credit: NAOJ with data processing by Masafumi Yagi (NAOJ)
Comet ISON may be no more than just a cloud of icy debris these days but there’s another comet that’s showing off in the morning sky: C/2013 R1 (Lovejoy), which was discovered in September and is steadily nearing its Christmas Day perihelion. In the early hours of Dec. 3, astronomers using the 8.2-meter Subaru Telescope atop Mauna Kea in Hawaii captured this amazing image of Lovejoy, revealing the intricate flows of ion streamers in its tail. (Click the image above for extra awesomeness.)
At the time of this observation, at around 5:30 am on December 3, 2013 (Hawaii Standard Time), Comet Lovejoy was 50 million miles (80 million km) distant from Earth and 80 million miles (130 million km) away from the Sun.
The entire image of comet Lovejoy was made with the Subaru Telescope’s Suprime-Cam, which uses a mosaic of ten 2048 x 4096 CCDs covering a 34′ x 27′ field of view and a pixel scale of 0.2”.
Where to find comet Lovejoy in the morning sky, Dec. 7 (via spaceweather.com)
“Subaru Telescope offers a rare combination of large telescope aperture and a wide-field camera,” said a member of the observation team, which included astronomers from Stony Brook University in New York, Universidad Complutense in Madrid, Johns Hopkins University, and the National Astronomical Observatory of Japan. “This enabled us to capture a detailed look at the nucleus while also photogenically framing inner portions of Comet Lovejoy’s impressive ion tail.”
Comet Lovejoy is currently visible in the early morning sky as a naked-eye object in the northern hemisphere.
Read more about Lovejoy’s journey through the inner solar system in this article by Bob King here.
Image of comet Lovejoy on Dec. 5 by Flickr user Willo2173.
Do you have photos of comet Lovejoy or any other astronomical objects to share? Upload them to the Universe Today Flickr group!
This images from the STEREO A spacecraft shows Comet ISON still visible on Dec. 3, 2013. Credit: NASA.
Could Comet ISON possibly still be alive? The latest high-resolution images available from the STEREO spacecraft are still showing some remains of the comet, although each day seems to show less and less activity. “If anything of ISON’s nucleus is left, it’s an inactive husk of a nucleus now,” Karl Battams from the Comet ISON Observing Campaign told Universe Today. “The comet remnant is fading fast in the STEREO data.”
Casey Lisse, also from CIOC was a bit more hopeful. In a web posting yesterday (Dec. 4) he said, “At this time, scientists are not sure how much of the comet survived intact. We may be seeing emission from rubble and debris in the comet’s trail, along its orbit, or we may be seeing the resumption of cometary activity from a sizable nucleus-sized chunk of ISON.”
Comet ISON, seen from the International Space Station over Ontario, on Nov 23, 2013 at about 85-mm, 10:08 UTC. Credit: NASA, via Peter Caltner.
Lisse added that most astronomers agree that Comet ISON was destroyed (with greater than 90% probability of this having occurred), leaving behind small (less than 10 m radius from the original 1 km nucleus) pieces of rubble, but there could be fragments 100 meters radius or larger. This would be big enough for astronomers to study but probably not big enough to provide a nice sky display later in December that everyone was hoping for.
Here’s the schedule of events for spacecraft to study whatever is left of Comet ISON, according to Lisse:
– NASA will monitor the comet for the next several weeks. If there is nothing sizable and stable left, it will dissipate and disappear in this time, as already emitted dust leaves the vicinity. If there is still a central source of emission, even if it is very much smaller, we will see a new, much fainter coma and tail form, which currently may be overwhelmed by the dust emitted from before the disruption event.
– NASA’s STEREO spacecraft will be using their cameras to search for bright fragments throughout the week, while the NASA Infrared Telescope Facility (IRTF) in Honolulu, Hawaii will use its 3m wide telescope to detect the comet spectroscopically, the same way it did on ISON’s inbound journey. Radio telescopes around the world will also be able to tell us more about what has happened. NASA’s recently launched MAVEN spacecraft may try to observe ISON next week. By mid- to late-December NASA’s Hubble and Chandra observatories will be performing deep outer space searches for any remnants of the comet. Spitzer will also look for ISON in early 2014.
If a fragment that acts like a comet is detected, but at a much reduced level, it may be hard to see it from the Earth at the time of its closest approach on December 26, 2013.
You can find out the latest on what is going on with ISON tomorrow, Dec. 6, 2013 as the CIOC is holding a post-perihelion workshop to discuss the status of the comet. The morning sessions, live from theh Applied Physics Lab at Johns Hopkins University will be webcast from approximately 8:30 am EST to 11:30 am EST, will be available for viewing in the player below:
More details on the meeting are available here.
So far, 12 spacecraft and the International Space Station have observed and detected Comet ISON on its multi-million year journey from the Oort Cloud to the solar corona. You can find out more about the planned Hubble observations here.
A montage of images of Comet ISON taken from September 24 to November 15, 2013. Credit and copyright: Damian Peach.
Astrophotographer Damian Peach has wowed us with his images of Comet ISON the past few months. Here’s a montage of some of his best images from September 24 to November 15.
“This may well be my final word on it.” Damian said via email, “but here it is growing in brightness on approach to its best in mid-late November.”
And while it appears there’s a ghost of ISON out there with a blob of dust in the latest views from the Sun-studying satellites, it won’t give us the views we had hoped for. But its been a fun experience the past few months, watching what unfolded. Thanks for bringing us along for the ride with your images, Damian!
Comet ISON appears much fainter in this SOHO image from 2:42 p.m. UTC (9:42 a.m. EST) on Nov. 30. Credit: ESA/NASA/SOHO
A brief morning update (EST) from Karl Battams, who studies sungrazing comets at the Naval Research Laboratory, confirms social media reports that Comet C/2012 S1 ISON appears to be getting fainter in images from the Solar and Heliospheric Observatory (SOHO). (To compare, you can see older images below the jump.)
“Comet #ISON really is fading fast and I no longer see any sign of a “central condensation” (i.e. no obvious indication of a nucleus…),” Battams wrote on Twitter. “I *do* think that something emerged from the Sun, but probably a v.small nucleus or “rubble pile”, and I fear that may have now dissolved.”
Astronomers wrote off Comet ISON on Thursday (Nov. 28) shortly after it rounded the sun, but it brightened considerably afterwards and researchers said it’s possible a small nucleus did survive the close encounter. Battams previously noted ISON’s behavior is much different than the other 2,000 or so sungrazers he’s observed.
The comet was discovered Sept. 21, 2012 by Artyom Novichonok and Vitali Nevski while conducting the International Scientific Optical Network (ISON) survey and has been the subject of intense speculation about its brightness prospects since.
Bright, brighter, brightest: these views of Comet ISON after its closest approach to the sun Nov. 28 show that a small part of the nucleus may have survived the encounter. Images from the Solar and Heliospheric Observatory. Credit: ESA/NASA/SOHO/GSFC
Bright, brighter, brightest: these views of Comet ISON after its closest approach to the sun Nov. 28 show that a small part of the nucleus may have survived the comet's close encounter with the sun. Images from the Solar and Heliospheric Observatory. Credit: ESA/NASA/SOHO/GSFC
Talk about the Comeback Kid. After Comet C/2012 S1 ISON rounded the sun yesterday afternoon, professional astronomers around the world looked at the faded debris and concluded it was an “ex-comet.” NASA wrapped up an hours-long Google+ Hangout with that news. The European Space Agency declared it was dead on Twitter.
But the remnants — or whatever ISON is now — kept brightening and brightening and brightening in images from the NASA/European Space Agency Solar and Heliospheric Observatory. The pictures are still puzzling astronomers right now, almost a day after ISON’s closest encounter with the sun.
You can follow our liveblogged confusion yesterday, capped by a gobsmacking announcement from the Naval Research Laboratory’s Karl Battams, “We believe some small part of ISON’s nucleus has SURVIVED perihelion,” he said on Twitter. Since then, Battams wrote a detailed blog post, referring to images from the Large Angle and Spectrometric Coronagraph (LASCO) aboard SOHO:
“Matthew [Knight] and I are ripping our hair out right now as we know that so many people in the public, the media and in science teams want to know what’s happened. We’d love to know that too! Right now, here’s our working hypothesis: As comet ISON plunged towards to the Sun, it began to fall apart, losing not giant fragments but at least a lot of reasonably sized chunks. There’s evidence of very large dust in the form of that long thin tail we saw in the LASCO C2 images.
After its closest approach to to the sun on Nov. 28 (left), Comet ISON appeared a dim shadow of its former self (at right). “The comet may still be intact,” NASA wrote on Nov. 29. Images from the Solar and Heliospheric Observatory. Credit: ESA/NASA/SOHO/Jhelioviewer
Then, as ISON plunged through the corona, it continued to fall apart and vaporize, and lost its coma and tail completely just like Lovejoy did in 2011. (We have our theories as to why it didn’t show up in the SDO images but that’s not our story to tell – the SDO team will do that.) Then, what emerged from the Sun was a small but perhaps somewhat coherent nucleus, that has resumed emitting dust and gas for at least the time being. In essence, the tail is growing back, as Lovejoy’s did.
So while our theory certainly has holes, right now it does appear that a least some small fraction of ISON has remained in one piece and is actively releasing material. We have no idea how big this nucleus is, if there is indeed one. If there is a nucleus, it is still too soon to tell how long it will survive. If it does survive for more than a few days, it is too soon to tell if the comet will be visible in the night sky. If it is visible in the night sky, it is too soon to say how bright it will be…
This morning (EST), Battams succinctly summarized the latest images he saw: “Based on a few more hours of data, comet #ISON appears to be… well, behaving like a comet!”, he wrote on Twitter.
NASA issued a status update this morning saying it’s unclear if this leftover is debris or an actual nucleus, but added that “late-night analysis from scientists with NASA’s Comet ISON Observing Campaign suggest that there is at least a small nucleus intact.” NASA, as well as Battams, pointed out that comet has behaved unpredictably throughout the 15 months scientists and amateurs have been observing it.
Mike Hankey of Monkton, Maryland took this photo of Comet ISON in outburst Nov. 14. The tail showed multiple streamers. Click to enlarge. Credit: Mike Hankey
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.
Slate Bad Astronomy blogger Phil Plait jokingly threw out phrases like “What the what?” on Twitter yesterday, but added in a late-night update: “If you haven’t figured this out yet: We are *loving* this. The Universe surprises us yet again! How awesome!” He continued with his astonishment in a blog post:
For those keeping score at home, it got bright, then it faded, then it got all smeared out, then it came around the Sun smeared out, and then it seemed to get its act together again. At this point, I refuse to make any further conclusions about this comet; it seems eager to confuse. I’ve been hearing from comet specialists who are just as baffled… which is fantastic! If we knew what was going on, there’d be nothing more to learn.
Science confusion: Comet ISON made its closest approach to the sun Nov. 28. Although it showed up again in images from the Solar and Heliospheric Observatory, scientists could not spot it using the ESA PROBA-2 spacecraft (view pictured). ISON’s composition or proximity to the sun may have caused this. Credit: PROBA-2 Science Centre
In a series of Twitter posts this morning, the European Space Agency’s science feed offered this take from Gerhard Schwehm, ESA’s head of planetary science:
From my initial look at ISON in today’s SOHO images, it seems nucleus has mostly disintegrated. Will only know if part of ISON nucleus has survived by continuing observations and performing more analysis. Bright fan-shape implies lots of material was released and travelling along ISON orbit, not confined in a traditional tail. Would be interesting to learn more about composition of debris to help us piece together what’s happened, but we need more time.
Image from SOHO indicates a chunk of Comet ISON has survived its close pass of the Sun. Credit: NASA/ESA/SOHO.
Update, 8:35 p.m. EST: Uncertainty about Comet ISON’s fate likely will persist for some time. Karl Battams just tweeted that after 2,000 sungrazing comet observations, he has never seen brightening in the same way that ISON (or its remains) appear to be doing right now. We’ll keep watching. Real-time images are available on this website.
Update, 6:30 p.m. EST: An excellent blog post from Phil Plait (who writes the Bad Astronomy blog on Slate) summarizes his take of the comet’s fate; debris (most likely, he says) continues to show up in images. An except: “It held together a long time, got very bright last night, faded this morning, then apparently fell apart. This isn’t surprising; we see comets disintegrate often enough as they round the Sun. ISON’s nucleus was only a couple of kilometers across at best, so it would have suffered under the Sun’s heat more than a bigger comet would have. Still, there’s more observing to do, and of course much data over which to pore.”
Update, 4:40 p.m. EST:On Twitter, the European Space Agency (quoting SOHO scientist Bernhard Fleck) said the comet is gone. Separately, the Naval Research Laboratory’s Karl Battams posted that he thinks recent observations show debris from ISON, but not a nucleus. Astronomers are still monitoring, however.
Update, 3:56 p.m. EST: Something has emerged from perihelion, but the experts are divided as to whether it’s leftovers of ISON’s tail, or the comet itself. Stay tuned.
The fate of Comet C/2012 S1 ISON is uncertain. It made its closest approach to the sun today (Nov. 28) around 1:44 p.m. EST (6:44 p.m. UTC). As of Thursday night, what’s happening to the comet is still unclear, as observers try to keep up hopes for a good comet show in the next few weeks.
It will take a few more hours until NASA and other agencies can say for sure what the comet’s fate is. That said, there still is valuable science that can be performed if ISON has broken up — more details below the jump.
ISON coincided with American Thanksgiving, causing a lot of astronomers and journalists to work holiday hours while pundits made jokes about the comet being “roasted” along with the turkey. Meanwhile, amateur astronomer Stuart Atkinson — author of the Waiting for ISON blog — was among those eagerly awaiting the comet’s closest approach.
But as the comet made its closest approach, astronomers grew more and more skeptical than it had survived. Phil Plait (who writes the Bad Astronomy blog on Slate) pointed out that the comet’s nucleus appeared much dimmer than its tail in images from SOHO (Solar and Heliospheric Observatory), NASA’s sun-gazing spacecraft. This implied that the nucleus was disintegrating.
Plait and Karl Battams — a Naval Research Laboratory astrophysicist who operates the Sungrazing Comets Project — both participated in a NASA Google+ Hangout on ISON. As of about 2 p.m. EST (7 p.m. UTC), both said that they believe ISON is an “ex-comet”, although it will be a few more hours before scientists can say for sure.
The challenge is that the two spacecraft used to watch ISON swing around the sun — the Solar Dynamics Observatory and SOHO — are not necessarily designed to look for comets. Battams and Plait initially said that it sometimes take additional image processing to view information in it. more As time elapsed though, both expressed extreme skepticism that the comet survived.
Even if the comet is dead, Plait pointed out that scientists can still learn a lot from the remaining debris. ISON is believed to be a pristine example of bodies in the Oort Cloud, a vast body of small objects beyond the orbit of Neptune. Examining the dust in its debris trail could tell scientists more about the origins of the solar system.
“The fact that it’s broken up is really cool. There’s a lot we can learn from it and a lot we can get from it,” he said.
Battams added that ISON has been a very unpredictable comet, flaring up when people expected it would fade, and vice versa. “ISON is just weird. It has behaved unpredictably at times. When it’s done something strange, we spent some time scratching our heads, figuring out what is going on and we think we know what it’s doing … it then goes and does something different.”
Amid the waiting came the inevitable social media jokes (including science fiction and fantasy references.)
For others, the comet served as an inspiration for daring to be courageous.
ISON: A 2013 pre-perihelion portrait. (Credit and copyright: Efrain Morales/Jaicoa observatory. Used with permission).
“ISON Lives!!!”
“ISON R.I.P…”
Those are just some of the possible headlines that we’ve wrestled with this week, as Comet C/2012 S1 ISON approaches perihelion tomorrow evening. It’s been a rollercoaster ride of a week, and this sungrazing comet promises to keep us guessing right up until the very end.
Comet ISON reaches perihelion on U.S. Thanksgiving Day Thursday, November 28th at around 18:44 Universal Time/ 1:44 PM Eastern Standard Time. ISON will pass 1.2 million kilometres from the surface of the Sun, just over eight times farther than Comet C/2011 W3 Lovejoy did in 2011, and about 38 times closer to the Sun than Mercury reaches at perihelion.
Comet ISON as seen from Ottawa, Canada on the morning of November 20th. (Credit: Andrew Symes/@FailedProtostar).
Earth-based observers essentially lost sight of ISON in the dawn twilight this past weekend, and there were fears that the comet might’ve disintegrated all together as it was tracked by NASA’s STEREO spacecraft. Troubling reports circulated early this week that emission rates for the comet had dropped while dust production had risen, possibly signaling that fragmentation of the nucleus was imminent. Certainly, this comet is full of surprises, and our observational experience with large sungrazing comets of this sort is pretty meager.
ISON (entering frame, to the right) currently “photobombing” SOHO’s LASCO C3 camera. Credit: NASA/ESA/SOHO.
However, as ISON entered the field of view of the Solar and Heliospheric Observatory’s LASCO C3 camera earlier today it still appeared to have some game left in it. NASA’s Solar Dynamics Observatory will pick up ISON starting at around 17:09UT/12:09 PM EST tomorrow, and track it through its history-making perihelion passage for just over two hours until 19:09UT/2:19PM EST.
And just as with Comet Lovejoy a few years ago, all eyes will be glued to the webcast from NASA’s Solar Dynamics Observatory as ISON rounds the bend towards its date with destiny… don’t miss it!
Note: you can also follow ISON’s current progress as seen from SOHO at their website!
The tracking plan for the Solar Dynamics Observatory on November 28th as ISON passes through perihelion. (Credit: NASA/SDO).
For over the past year since its discovery, pundits have pondered what is now the astronomical question of the approaching hour: just what is ISON going to do post-perihelion? Will it dazzle or fizzle? In this context, ISON has truly become “Schrödinger’s Comet,” both alive and dead in the minds of those who would attempt to divine its fate.
Recent estimates place ISON’s nucleus at between 950 and 1,250 metres in diameter. This is well above the 200 metre size that’s considered the “point of no return” for a comet passing this close to the Sun. But again, another key factor to consider is how well put together the nucleus of the comet is: a lumpy rubble pile may not hold up against the intense heat and the gravitational tug of the Sun!
Current updated light curve for ISON. Be sure to check with NASA’s Comet ISON Observing Campaign for the latest updates. (Compiled by Matthew Knight on November 24th, 2013).
But what are the current prospects for spotting ISON after its fiery perihelion passage?
If the comet holds together, reasonable estimates put its maximum brightness near perihelion at between magnitudes -3 and -5, in the range of the planet Venus at maximum brilliancy. ISON will, however, only stand 14’ arc minutes from the disk of the Sun (less than half its apparent diameter) at perihelion, and spying it will be a tough feat that should only be attempted by advanced observers.
Note that for observers based at high northern latitudes “north of the 60,” the shallow angle of the ecliptic might just make it possible to spot Comet ISON low in the dawn after perihelion and before sunrise November 29th:
ISON post-perihelion at sunrise on November 29th as seen from Fairbanks, Alaska. (Created using Starry Night Education software.
We’ve managed to see the planet Venus the day of solar conjunction during similar circumstances with the Sun just below the horizon while observing from North Pole, Alaska.
Most northern hemisphere observers may catch first sight of Comet ISON post-perihelion around the morning of December 1st. Look low to the east, about half an hour before local sunrise. Use binoculars to sweep back and forth on your morning comet dawn patrol. Note that on December 1st, Saturn, Mercury, and the slim waning crescent Moon will also perch nearby!
Comet ISON, Mercury, Saturn and the Moon: looking east on the morning of December 1st as seen from latitude 30 degrees north. (Created using Starry Night Education software).
Comet ISON will rapidly gain elevation on successive mornings as it heads off to the northeast, but will also rapidly decrease in brightness as well. If current projections hold, ISON will dip back below magnitude 0 just a few days after perihelion, and back below naked eye visibility by late December. Observers may also be able to start picking it up low to the west at dusk by mid-December, but mornings will be your best bet.
The path of comet ISON for the first week of December as seen from latitude 30 degrees north. Note: the planets and the Moon are depicted for December 1st. (Created using Stellarium).
Keep in mind, if ISON fizzles, this could become a “death-watch” for the remnants of the comet, as fragments that might only be visible with binoculars or a telescope follow its outward path. If this turns out to be the case, then the best views of the “Comet formerly known as ISON” have already occurred.
Another possible scenario is that the comet might fragment right around perihelion, leaving us with a brief but brilliant “headless comet,” similar to W3 Lovejoy back in late 2011. The forward light scattering angle for any comet is key to visibility, and in this aspect, ISON is just on the grim edge in terms of its potential to enter the annals of “great” comets, such as Comet Ikeya-Seki back in 1965.
ISON will then run nearly parallel to the 16 hour line in right ascension from south to north through the month of December as it crosses the celestial equator, headed for a date with the north celestial pole just past New Years Day, 2014.
Whether as fragments or whole, comets have to obey Sir Isaac and his laws of physics as they trace their elliptical path back out of the solar system. Keep in mind, a comet’s dust tail actually precedes it on its way outbound as the solar wind sweeps past, a counter-intuitive but neat concept we may just get to see in action soon.
Here are some key dates to watch for as ISON makes tracks across the northern hemisphere sky. Passages are noted near stars brighter than +5th magnitude and closer than one degree except as mentioned:
The celestial path of ISON from November 29th to December 15th. (Credit: Starry Night).
December 1st: ISON is grouped with Saturn, Mercury and the slim crescent Moon in the dawn.
December 2nd: Passes near the +4.9 magnitude star Psi Scorpii.
December 3rd: Passes into the constellation Ophiuchus.
December 5th: Passes near the +2.7 magnitude multiple star Yed Prior.
December 6th: Crosses into the constellation Serpens Caput.
December 8th: Crosses from south to north of the celestial equator.
December 15th: Passes into the constellation Hercules and near the +5th magnitude star Kappa Herculis.
December 17th: The Moon reaches Full, marking the middle of a week with decreased visibility for the comet.
December 19th: Passes into the constellation of Corona Borealis.
December 20th: Passes near the +4.8th magnitude star Xi Coronae Borealis.
December 22nd: Passes 5 degrees from the globular cluster M13. Photo op!
The path of Comet ISON from December 16th to January 8th. (Credit: Starry Night).
December 23rd: Crosses back into the constellation Hercules.
December 24th: Passes near the +3.9 magnitude star Tau Herculis.
December 26th: Comet ISON passes closest to Earth at 0.43 A.U. or 64 million kilometres distant, now moving with a maximum apparent motion of nearly 4 degrees a day.
December 26th: Crosses into the constellation Draco and becomes circumpolar for observers based at latitude 40 north.
December 28th: Passes the +2.7 magnitude star Aldhibain.
December 29th: Passes the +4.8 magnitude star 18 Draconis.
December 31st: Passes the 4.9 magnitude star 15 Draconis.
January 2nd: Crosses into the constellation Ursa Minor.
January 4th: Crosses briefly back into the constellation Draco.
January 6th: Crosses back into the constellation Ursa Minor.
January 7th: Crosses into Cepheus; passes within 2.5 degrees of Polaris and the North Celestial Pole.
And after what is (hopefully) a brilliant show, ISON will head back out into the depths of the solar system, perhaps never to return. Whatever the case turns out to be, observations of ISON will have produced some first-rate science… and no planets, popes or prophets will have been harmed in the process. And while those in the business of predicting doom will have moved on to the next apocalypse in 2014, the rest of us will have hopefully witnessed a dazzling spectacle from this icy Oort Cloud visitor, as we await the appearance of the next Great Comet.
Enjoy the show!
ISON: “Great Comet” or “Great Pumpkin?” Photo and gourd-based artwork by author.
Comet ISON joins Earth and Mercury in this photo made by NASA's STEREO-A (Ahead) spacecraft in the early morning hours of Nov. 23, 2013. Click to see additional images.
The day of truth is fast approaching. Will Comet ISON’s sungrazing ways spark it to brilliance or break it to bits? How bright will the comet become? Studying the latest images from NASA’s STEREO Ahead sun-watching spacecraft, it’s obvious that ISON remains healthy and intact. The most recent pictures taken from the ground confirm that no major breakup has occurred. Assuming that ISON doesn’t crumble apart on Nov. 28, when it passes just 730,000 miles (1.2 million km) from the sun, it could brighten to -4 magnitude or better in the hours leading up to and after the moment of perihelion at 12:24:57 p.m. CST (18:24:57 UT).
This beautiful photo of Comet ISON was taken from a mountaintop observatory with a 300mm lens by Juan Carlos Casado of Spain on Nov. 24, 2013. Casado “stacked” or composited four photos to enhance the brightness of the comet against twilight. Click to enlarge.
For comparison, the planet Venus hovers around -4 magnitude and is routinely visible visible with the naked eye in broad daylight if you know exactly where to look. For the sake of establishing a baseline, let’s imagine that ISON will match Venus in magnitude during its crack-the-whip fling around the sun. Naturally, this would put the comet within range of naked eye visibility smack in the middle of the day. Well, maybe. ISON presents us with a little problem. While it may grow bright enough to view in daylight, it will be very close to the sun on perihelion day. Not only will it be difficult to tease from the solar glare, but with the sun only a degree or two away, there’s a real danger you could damage your eyes if you stray too close.
Comet ISON swings rapidly around the sun on perihelion day Nov. 28. Positions are shown hourly with north up and west to the right. Created with Chris Marriott’s SkyMap software
During the early morning hours of the 28th, ISON will lie approximately 2.5 degrees from the sun’s limb or edge. At the time of perihelion that separation narrows to less than 1/2 degree or one solar diameter. This is likely when the comet will shine brightest, but with the sun so close, it will be next to impossible to spot it with naked eye or binoculars at that time. Matter of fact, don’t even try – it’s not worth the risk of damaging your retinas. An expert observer with a carefully-aimed telescope might pick it up, but must use extreme caution that sunlight not enter the field of view. Come sunset, the distance widens again to a somewhat more comfortable 2.5 degrees.
Once, when following Venus as a crescent through inferior conjunction, I dared track it within 2.5 degrees of the sun. THAT was almost too close for comfort. I had to avert my vision from a brilliant wedge of internally reflected sunlight along one side of the view and wear sunglasses to temper the brilliance of the “safe zone” where Venus appeared.. Red and polarizing filters can help reduce glare and increase contrast for near-sun viewing of comets and planets.
Comet McNaught on Jan. 13, 2007 photographed with a 500mm lens. “Comet was easily visible by naked eye,” said photographer Mark Vornhusen of Gais, Switzerland. Will ISON give us a similar show? Click to enlarge. Credit: Mark Vornhusen / Wikipedia
In mid-January 2007, Comet C/2006 P1 McNaught had a similar close brush with the sun and peaked around magnitude -5. For several days around perihelion on Jan. 12 it was plainly visible with the naked eye in broad daylight. I spotted it 5.6 degrees from the sun at magnitude -3.5 (twice as faint as Venus) at 10 a.m. on Jan. 13 and 5 degrees from the sun the following day when I estimated its magnitude at -4.5. While close, 5 degrees is a much more comfortable distance for comet and inner planet viewing.
Example using a rooftop to block the sun. When using binoculars for daytime comet hunting, BE SURE you focus them first at infinity otherwise there’s no way to know if the comet will be in focus. I use clouds (the best) or a distant treeline. Credit: Bob King
Whether naked eye, binocular or telescope, the favorite method for finding Comet McNaught in 2007 remains the best for Comet ISON in 2013. Block out the sun by placing something with a crisp edge in its way. Power poles, street lights (finally a good use for them), buildings, roof gables, church steeples and even clouds make ideal sun filters. They effectively remove the sun and allow you to look as close as is safe. Safety is critical here – never look directly at the sun. The damage to your retina will be swift and painless. No comet is worth losing your precious sense of sight.
As Earth rotates, the sun slowly moves across the sky. When using binoculars, if you start to see a bright reflection from approaching sunlight in the field of view, shift your position and re-cover the sun. I’ve been asked if you can simply hold an appropriate solar filter over your eye to dim the sun. Yes you can, but the filter will also completely block your view of the much, much fainter comet. Use the filter instead to dim the sun so you can hunt nearby for the comet.
Use these little pictures to help you know what direction from the sun to look for Comet ISON between 8 a.m. and 2 p.m. CST Thursday Nov. 28. Add one hour for Eastern time; subtract 1 hour for Mountain and 2 hours for Pacific. Be sure to face the direction shown when using the diagrams and completely block the sun from view. StellariumOur final view shows the comet shortly before sunset in the southwestern sky when it lie about 2-2.5 degrees directly above the sun. Time is 4 p.m. CST
Since ISON will be 2.5 degrees from the sun in the early morning and again just before sunset, those might be the best times to find it. Compared to the hour or two around perihelion, the glare will be less though ISON will likely be a little fainter. You can use the diagram above, suitable for mid-northern latitudes, to know in what direction from the sun to look for the comet. If ISON becomes at least as bright as Venus and your sky is deep blue and haze-free, you might just see it on Thursday before sitting down to that Thanksgiving turkey dinner. But of course much depends upon the comet.
Comet ISON will be under constant view Nov. 27-30 in the SOHO coronagraph, an instrument that blocks the sun so scientists can study the near-solar environment. Click to see images. Credit: NASA/ESA
Don’t fret if it’s cloudy. Head over to the Solar and Heliospheric (SOHO) website. There you’ll have a ringside seat Nov. 27-30 as Comet ISON makes its death-defying turn around the sun. Thereafter it will appear risk-free in the morning sky with what we hope will be a beautiful tail.
A last look at Comet ISON before dawn on November 23, 2013 from the Canada France Hawaii Telescope on the summit of Mauna Kea, Hawaii. Credit: CFHT/CometISON Twitter feed.
Comet ISON is heading towards its inexorable close pass of the Sun, which will occur on November 28, 2013. And while we’ve been enjoying great views from astrophotographers, that luxury is probably over as of today, as the comet is just getting to close to the Sun — and its blinding glare — for us to see it. But while we won’t be able to see it from Earth, we’re lucky to have a fleet of spacecraft that will be able to keep an eye on the comet for us! The STEREO spacecraft has already taken images of ISON hurtling towards the Sun; the Solar and Heliospheric Observatory (SOHO) will start observations on November 27. Then, the Solar Dynamics Observatory (SDO) will view the comet for a few hours during its closest approach to the Sun, and the X-Ray telescope on the Hinode spacecraft will view Comet ISON for about 55 minutes during perihelion.
Above is a gorgeous timelapse of ISON from the Teide observatory in the Canary Islands on Nov. 22nd, 2013. See more images and videos below.
Above is a screenshot from the live camera views from the Canada France Hawaii Telescope webcam. You can see a live view from their webcam any time at this link.
A montage of images of Comet ISON, taken from January-May and then September to late November. Credit and copyright: Efrain Morales/Comet ISON seen on November 22, 2013 from Corvalis, Oregon, USA. Manual alignment of 20 frames of 4 seconds each in Deep Sky Stacker. Credit and copyright: A Nartist on Flickr.Comet ISON (C/2012 S1) in the morning twilight, above centre, with Mercury above the trees at left of frame. Taken from home in southern Alberta, November 21, 2013, using the 135mm lens at f/2.8 and Canon 5D MkII at ISO 1600 for stack of 5 x 4 second exposures, tracked with the iOptron SkyTracker, with the ground from one exposure to avoid blurring from the tracking motion. Credit and copyright: Alan Dyer/Amazing Sky Photography.Comet C/2012 S1 (ISON) plus possible fragmentation or disconnect event on Nov 21, 2013, taken from New Mexico. Credit and copyright: Joseph Brimacombe.A glimpse of ISON from the Netherlands on November 21, 2013. Credit and copyright: Fred Kamphues.Comet ISON and Spica together during Full Moon on November 18, 2013, seen from Payson, Arizona. Credit and copyright: Chris Schur.
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