ISON Archives

December 30, 2013December 23, 2015 by David Dickinson

The Quadrantid Meteor Shower-One of the Best Bets for 2014

The modern radiant of the Quadrantid meteor shower. (Photo and grahpics by author).

If there’s one thing we love, it’s a good meteor shower from an obscure and defunct constellation.

Never heard of the Quadrantids? It may well be because this brief but intense annual meteor shower occurs in the early days of January. Chilly temps greet any would be meteor watchers with hardly the balmy climes of showers such as the August Perseids. Still, 2014 presents some good reasons to brave the cold in the first week of January, to just possibly catch the best meteor shower of the year.

The Quadrantids – sometimes simply referred to as “the Quads” in hipster meteor watcher inner circles – peak on January 3^rd around 19:30 Universal Time (UT) or 2:30 PM Eastern Standard Time (EST). This places the northern Asia region in the best position to watch the show, though all northern hemisphere observers are encouraged to watch past 11 PM local worldwide. Remember: meteor showers are fickle beasties, with peak activity often arriving early or late. The Quadrantids tie the December Geminids for the highest predicted Zenithal Hourly Rate (ZHR) for 2014 at 120.

A 2012 Quadrantid meteor in the bottom left side of the frame. (Photo by Author).

Though the Quads are active from January 1^st to the 10^th, the enhanced peak only spans an average of six to ten hours. Though high northern latitudes have the best prospects, we’ve seen Quads all the way down in the balmy January climes of Florida from around 30 degrees north.

Rates for the Quads are typically less than 10 per hour just a day prior to the sharp peak. The moonless mornings of Friday, January 3^rd and Saturday, January 4^th will be key times to watch. The radiant for the Quads stands highest just hours before local sunrise.

So, what’s up with the unwieldy name? Well, the Quadrantids take their name from a constellation that no longer exists on modern star charts. Along with the familiar patterns such as Leo and Orion, exist such archaic and obscure patterns as “The Printing Office” and the “Northern Fly” that, thankfully, didn’t make the cut. Quadrans Muralis, or the Mural Quadrant, established by Jérome de Lalande in the 1795 edition of Fortin’s Celestial Atlas was one such creation. A mural quadrant was a large arc-shaped astronomical tool used for measuring angles in the sky. Apparently, Renaissance astronomers were mighty proud of their new inventions, and put immortalized them in the sky every chance they got as sort of the IPhone 5’s of their day.

The outline of the Mural Quadrant against the backdrop of modern day constellations. (Photo and graphic by author).

The Mural Quadrant spanned the modern day constellations of Draco, Hercules and Boötes. The exact radiant of the Quads lies at Right Ascension 15 Hours 18’ and declination 49.5 degrees north, in the modern day constellation Boötes just 15 degrees east of the star Alkaid.

Previous year’s maximum rates as per the IMO have been as follows:

2013: ZHR=129

2012: ZHR=83

2011: ZHR=90

2010: ZHR=No data (Bright waning gibbous Moon)

2009: ZHR=138

The parent source of the Quadrantids went unknown, until Peter Jenniskens proposed that asteroid 2003 EH1 is a likely suspect. Possibly an extinct comet, 2003 EH1 reaches perihelion at 1.2 AUs from the Sun in 2014 on March 12^th, another reason to keep an eye on the Quads in 2014. 2003 EH1 is on a 5.5 year orbit, and it’s been proposed that the asteroid may have a connection to comet C/1490 Y1 which was observed and recorded by 15th century astronomers in the Far East.

The Quadrantids were first identified as a distinct meteor shower in the 1830s by European observers. Owing to their abrupt nature and their climax during the coldest time of the year, the Quadrantids have only been sporadically studied. It’s interesting to note that researchers modeling the Quadrantid meteor stream have found that it undergoes periodic oscillations due to the perturbations from Jupiter. The shower displays a similar orbit to the Delta Aquarids over a millennia ago, and researchers M. N. Youssef and S. E. Hamid proposed in 1963 that the parent body for the shower may have been captured into its present orbit only four thousand years ago.

The orbital path of Amor NEO asteroid 196256 2003 EH1. (Credit: NASA/JPL Solar System Dynamics Small-Body Database Browser).

2003 EH1 is set to resume a series of close resonnance passes of Earth and Jupiter in 2044, at which time activity from the Quads may also increase. It’s been proposed that the shower may fade out entirely by the year 2400 AD.

And the Quadrantids may not be the only shower active in the coming weeks. There’s been some discussion that the posthumous comet formerly known as ISON might provide a brief meteor display on or around the second week of January.

Be sure to note any meteors and the direction that they’re coming from: the International Meteor Organization and the American Meteor Society always welcomes any observations. Simple counts of how many meteors observed and from what shower (Quads versus sporadics, etc) from a given location can go a long way towards understanding the nature of this January shower and how the stream is continually evolving.

Stay warm, tweet those meteors to #Meteorwatch, and send those brilliant fireball pics in to Universe Today!

December 30, 2013December 23, 2015 by Bob King

Jan. 16 May Be Last Best Chance to Search for Comet ISON’s Remains

Comet ISON revolves around the sun in steeply inclined orbit. Earth will pass through the plane of that orbit on Jan. 16. As we look "up" toward the comet our edgewise perspective could cause a temporary brightening of ISON's dust remnant. Credit: solarsystemscope.com with annotations by the writer.

Is there any hope of detecting what’s left of Comet ISON after the sun proved too much for its delicate constitution? German amateur astronomer Uwe Pilz suggest there remains a possibility that a photographic search might turn up a vestige of the comet when Earth crosses its orbital plane on January 16, 2014.

Update: See an image below taken by Hisayoshi Kato of the comet’s location in Draco on December 29!

Comet ISON is located high in the northern sky near the familiar "W" or "M" or Cassiopeia during the time of orbital crossing. Stellarium — Comet ISON is located high in the northern sky near the familiar “W” or “M” or Cassiopeia during the time of orbital crossing. Stellarium

On and around that date, we’ll be staring straight across the sheet of debris left in the comet’s path. Whatever bits of dust and grit it left behind will be “visually compressed” and perhaps detectable in time exposure photos using wide-field telescopes. To understand why ISON would appear brighter, consider the bright band of the Milky Way. It stands apart from the helter-skelter scatter of stars for the same reason; when we look in its direction, we peer into the galaxy’s flattened disk where the stars are most concentrated. They stack up to create a brighter band slicing across the sky. Similarly, dust shed by Comet ISON will be “stacked up” from Earth’s perspective on the 16th.

Comet L4 PanSTARRS bizarre beam-like appearance on May 28 near the time of orbital plane crossing. Credit: Michael Jaeger — Comet L4 PanSTARRS beam-like appearance on May 28 near the time of orbital plane crossing. Credit: Michael Jaeger

This isn’t the first time a comet has leapt in brightness at an orbital plane crossing. You might recall that Comet C/2011 L4 PanSTARRS temporarily brightened and assumed a striking linear shape when Earth passed through its orbital plane on May 27.

Comet ISON debris simulations for Jan. 12 and 14, 2014. Credit: Uwe Pilz — Comet ISON debris simulations for Jan. 12 and 14, 2014. The aqua line points toward the sun; the black line is 1 degree long. Credit: Uwe Pilz

Pilz, a longtime contributor to the online Comets Mailing List for dedicated comet observers, has made a series of simulations of Comet ISON for mid-January using his own comet tail program. He bases his calculations on presumed larger particle sizes 1 mm – 10 mm – not the more common 0.3-10 micrometer fragments normally shed by comets. The assumption here is that ISON has remained virtually invisible since perihelion because it broke up into a smaller number of larger-than-usual pieces that don’t reflect light nearly as efficiently as larger amounts of smaller dust particles.

A slivery ISON on Jan. 16 widens a bit two days later in Pilz's simulations. Credit: Uwe Pilz — A slivery ISON on Jan. 16 widens a bit two days later in Pilz’s simulations. Click to see additional simulations. Credit: Uwe Pilz

The images look bizarre at first glance but totally make sense given the unique perspective. Notice that the debris stream becomes thinner as we approach orbital crossing; any potential dust blobs appear exactly edge-on similar to the way Saturn’s rings narrow to a “line” when Earth passes through the ring plane.

Besides the fact that not a single Earth-bound telescope has succeeded to date in photographing any of ISON’s debris, amateurs who attempt to fire one last volley the comet’s way will face one additional barrier – the moon. A full moon the same day as orbital crossing will make a difficult task that much more challenging. Digital photography can get around moonlight in many circumstances, but when it comes to the faintest of the faint, the last thing you want in your sky is the high-riding January moon. One night past full, a narrow window of darkness opens up and widens with each passing night.

Will anyone take up the challenge?

UPDATE Dec. 30 10 a.m. (CST): We may have our very first photo of Comet ISON from the ground! Astrophotographer Hisayoshi Kato made a deep image of the comet’s location in Draco on December 29 using a 180mm f/2.8 telephoto lens near the Mauna Loa Observatory in Hawaii at 11,000 feet. He stacked 5 exposures totaling 110 minutes to record what could be the ISON’s debris cloud. It’s incredibly diffuse and faint and about the same brightness as the Integrated Flux Nebula, dust clouds threading the galaxy that glow not by the light of a nearby star(s) but instead from the integrated flux of all the stars in the Milky Way. We’re talking as dim as it gets. What the photo recorded is only a tentative identification – followup observations are planned to confirm whether the object is real or an artifact from image processing. Stay tuned.

The sausage-like glow running from upper left to lower right in this negative image may the dusty remains of Comet ISON as photographed on Dec. 29 from Hawaii. Click to enlarge. Credit: Hisayoshi Kato — The sausage-like glow running from upper left to lower right in this negative image may the dusty remains of Comet ISON as photographed on Dec. 29 from Hawaii. The blue dot shows the predicted position of the comet; the green type gives the names of stars. Click to enlarge. Credit: Hisayoshi Kato

December 20, 2013December 23, 2015 by Bob King

Hubble Looks but Finds No Trace of Comet ISON

Each of the four panels is a combination of two separate exposures made by the Hubble Space Telescope as it tracked Comet ISON's position. Had the comet been in any of these frames, it would have appeared as a small fuzzy glow or stellar point(s) in the center. The stars are trailed because the camera tracked the comet. Credit: NASA/ESA

On December 18, the Hubble Space Telescope slewed to Comet ISON’s expected position and found nothing down to the incredibly faint magnitude of 25. According to astronomer Hal Weaver, who planned the ISON search, that limit implies any remaining fragments would have to be smaller than about 500 feet (160 meters) in diameter.

Composite photo of one of two Comet ISON locations photographed by the Hubble in a way that suppresses features not in the same place. No trace of the comet is visible. Credit: NASA/ESA — Composite photo of one of two Comet ISON locations photographed by the Hubble Space Telescope. No trace of the comet is visible. Credit: NASA/ESA

Nothing is visible in any of the images in the photo panel except trailed stars and galaxies, reflections and the occasional zap of a cosmic ray. After ISON was torn asunder by the sun, there existed the possibility that comet’s remains would follow a slightly different orbit. To make sure he was covered, Weaver photographed two separate comet positions, stacking several exposures together.

Comet ISON photographed at a second location. Again, nothing detected. Credit: NASA/ESA

“The images have been combined so that features not at the same place in the various images are suppressed. Any comet fragments would show up more clearly in this composite, though stars still show up as faint streaks”, writes Zolt Lavay, author of the ISONblog at the Hubble site.

Again, nothing shows up in these either. While no one can say that ISON has completely disappeared, we now know that at the very least it’s broken into pieces too small for even Hubble to see. What was once a beautiful sight in binoculars has expanded into a vast cloud of gas and dust thinner than Ebenezer Scrooge’s gruel.

December 17, 2013December 23, 2015 by Elizabeth Howell

Comet Tourism Flight Trades ISON For Lovejoy

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

When Comet ISON entered its zombie stage a few weeks ago, the effects were not only felt in the astronomical community, but also on astronomy tourists as the comet faded from the view of amateurs.

German company “Eclipse-Reisen” (Eclipse Travel) had to make a last-minute change in plans for a Dec. 8 flight for some 75 tourists planning to observe ISON, which morphed into a travelling dust blob after skimming too close to the sun in late November. Fortunately, Comet Lovejoy is still a strong astronomical object, providing an alternate thing to watch.

“Most of the passengers weren’t disappointed. They were more excited to see something new. Only a few journalists cancelled the flight. All photographers and experts fully understood the situation,” a statement from Air Partner to Universe Today said. (The spokespeople were German-speaking, requiring a translation by another party.)

Negative image taken Nov. 14 of Lovejoy's nucleus and dust fan. Credit: Dr. P. Clay Sherrod — Negative image taken Nov. 14 of Lovejoy’s nucleus and dust fan. Credit: Dr. P. Clay Sherrod

“Comet Lovejoy is no less spectacular and still very exciting like ISON and they were pleased to see it, actually. Although Lovejoy is less bright than ISON, it is weaker by four size classes, its tail is smaller and pale and Lovejoy flies farther past the Earth and the Sun.”

The company had to ask for permission to alter its flight path, and inform the passengers of the last-minute change, all in a few days, but officials added that the flight went off without a hitch.

You can read more information about the company (in German) on its website. In 2014, it plans to run a flight to observe auroras over Iceland, among others.

December 5, 2013December 23, 2015 by Nancy Atkinson

Is Anything Left of ISON? Spacecraft Continue to Monitor Comet’s Remains

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:

Watch live streaming video from cometison at livestream.com

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.

December 2, 2013December 23, 2015 by Nancy Atkinson

Gorgeous Astrophoto: Montage of Comet ISON

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!

November 30, 2013December 23, 2015 by Elizabeth Howell

ISON Appears To Be Fading, But Astronomers Keeping Eyes Peeled

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.”

This comet, however, has defied predictions over and over again. We’ll keep you posted as to its progress.

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.

November 29, 2013December 23, 2015 by Elizabeth Howell

Zombie ISON ‘Behaving Like A Comet’, Stunned Astronomers Say

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.

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 this morning Nov. 14. The tail now shows multiple streamers. Click to enlarge. Credit: Mike Hankey — 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 — 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.

Other spacecraft searching for ISON were not able to spot it. For ESA’s PROBA-2, it may have been because of its composition or proximity to the sun, but scientists are unsure. It was also invisible in NASA’s Solar Dynamics Observatory; “scientists are still looking at the data to figure out why,” an agency Twitter update stated this morning.

So to sum up: no one’s quite sure of what is happening now, or what is happening next, but we will keep you posted and let you know if and when you can see ISON again in your home telescopes.

One of the finest pictures to date of Comet ISON by ace astrophotographer Damian Peach taken on Oct. 27.

November 28, 2013December 23, 2015 by Elizabeth Howell

Is Comet ISON Dead? Astronomers Say It’s Likely After Icarus Sun-Grazing Stunt

Comet ISON on Nov. 10 before the recent outburst with well-developed dust (upper) and gas tails. Click ot enlarge. Credit: Damian Peach

Update, 9:55 pm EST: It’s a Thanksgiving miracle: apparently it now looks like ISON has actually survived!!

Alright we're calling it, and you heard it here first: We believe some small part of #ISON's nucleus has SURVIVED perihelion.

— Sungrazer Comets (@SungrazerComets) November 29, 2013

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.

November 27, 2013December 23, 2015 by David Dickinson

ISON Watch: A Post-Perihelion Viewing Guide

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 28^th 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.

Credit: SOHO — 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). — 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 29^th:

ISON Perihelion 1730UT Fairbanks — 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 1^st. 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 1^st, Saturn, Mercury, and the slim waning crescent Moon will also perch nearby!

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.

ISON path — 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 +5^th magnitude and closer than one degree except as mentioned:

November 29th through December 15th. — 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 +5^th 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 +4.8^th magnitude star Xi Coronae Borealis.

December 22nd: Passes 5 degrees from the globular cluster M13. Photo op!

Dec 16-Jan 8 — The path of Comet ISON from December 16th to January 8th. (Credit: Starry Night).

December 23^rd: Crosses back into the constellation Hercules.

December 24^th: Passes near the +3.9 magnitude star Tau Herculis.

December 26^th: 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 26^th: Crosses into the constellation Draco and becomes circumpolar for observers based at latitude 40 north.

December 28^th: Passes the +2.7 magnitude star Aldhibain.

December 29^th: Passes the +4.8 magnitude star 18 Draconis.

December 31^st: Passes the 4.9 magnitude star 15 Draconis.

January 2^nd: 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 the "Great Pumpkin?" Photo and gourd-based artwork by author. — ISON: “Great Comet” or “Great Pumpkin?” Photo and gourd-based artwork by author.

– Got question about Comet ISON? Lights in the Dark has answers!

– Be sure to post those amazing post-perihelion pics of Comet ISON on Universe Today’s Flickr page.