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Comet ISON – Timeline of events and best images since its discovery


November 30, 2013

ISON is fading and exiting LASCO C3 view.

08:18 UTC

Comet ISON on November 30, 2013 @ 08:18. Image credit: ESA/NASA SOHO

05:30 UTC

Karl Battams (NRL/CIOC) wrote and update on ISON and embeded cool gifs from STEREO: In ISON's Wake, a Trail of Questions

In terms of a timeline, in a few days time I think we'll be able to make a good call on the naked eye visibility of ISON (keep your expectations low, please…). In maybe a week or so I'm guessing we'll fully understand why ISON didn't put on a show in SDO (they might have already figured this out – I don't know – but that's their story to tell, not mine). Give us three or so weeks at least to (hopefully) get Hubble images to say if there's anything left of ISON, and how much, if so. Then expect results from the Comet ISON Observing Campaign to continue appearing for at least, oh, five years? Maybe ten… 

One of the questions answered there:

  • Will it be naked eye visible? When? How bright?
    This is definitely the toughest question but also the most frequent. We still don't know if it will be naked eye but based on its current brightness in the LASCO images – which is around magnitude +5 and fading – it does seem unlikely that there will be much to see in the night sky. I suspect that some of the outstanding astrophotographers around the world will be able to get something, but I doubt it will be as spectacular as before perihelion. I hope I'm wrong though. 

    I'd guess that a few observers will begin picking up ISON in a couple of days but if – and I do mean IF – comet ISON becomes naked eye visible, it won't be until near the end of next week (say, Dec 6 or 7). Please don't get your hopes up, but we all need to keep in mind how ISON keeps surprising us.

Comet ISON on November 30, 2013 @ 05:35 UTC. Image credit: ESA/NASA/SOHO SDO

01:15 UTC

NASA/SDO scientists are still looking at the data to figure out why ISON was not visible during its closest approach.

Below is the video of STEREO Behind COR2 capturing the close encounter from the approach, perihelion, and finally after a near death experience, the exit. Towards the end of the video you can see what appears to be the tail reforming and changing directions as the flow of the solar wind streams past it. 

YouTube video

Animation from SOHO's LASCO C2 and C3 coronographs indicate that ISON really is alive.

YouTube video

Latest images from LASCO C3 and C2
Latest images from LASCO C3 and C2 

[ESA/ESAC SOHO archive]

Since yesterday's 'resurrection,' the comet's overall dust output has clearly increased dramatically as compared with its pre-perihelion situation. John Bortle of Sky&Telescope magazine noted that comet is now experiencing a huge and ongoing dust release in a broad range particle sizes.  If ISON continues to exhibit intense dust production and retains sufficient ices to drive activity for a short time, a broad tail of considerable size may quickly develop.  It would be impressive mainly from dark-sky observing sites due to rapidly diminishing surface brightness as the object withdraws from the Sun. The comet's 'head' will probably be tiny in comparison with the tail and might even be difficult to define with the unaided eye.

Where to try looking for Comet ISON very low in bright dawn on the morning of December 1st. Mercury, Saturn, and the Moon will be much brighter; start with them to find the spot to examine for the comet with binoculars.  (Courtesy of SkyandTelescope.com)

November 29, 2013

20:09 UTC

Image credit: ESA/NASA/SOHO

SDO's Dean Pesnell posted update about why we didn't see anything on SDO imagery during ISON's perihelion:

By now I am sure people are aware that something continues to move along the orbit of Comet ISON in the LASCO observations. It is being discussed whether it is debris from Comet ISON or a remnant. In either case we should try to understand why we didn't see that debris or remnant as it went through perihelion yesterday.

When SDO looks for a comet it does not see the dust and ion tails seen in a comet far from the Sun. We see oxygen ions, oxygen atoms with some electrons stripped off, glowing when they are hit by the hot electrons in the corona. The AIA telescopes normally look at iron ions, but the enormous amount of oxygen that comes off a comet allows that element to emit brighter for a while after the comet passes.

The images we showed yesterday were our best guesses for which AIA passbands would show bright emissions from Comet ISON as it flew past the Sun. They are the passbands that showed Comet Lovejoy in December 2011 and the earlier comet in June 2011. All four passbands would show emission from O IV, O V, or O VI, oxygen atoms with 3, 4, or 5 electrons removed. This is a chain, where O V is produced from O IV and then O VI is produced from O V.

We pointed SDO at three locations along the projected orbit. If you compare the predicted orbit with the SOHO images it looks like we had pretty good alignment. I was watching how the comet moved along its predicted orbit as we changed the SDO pointing and the comet moved through the frames we provided. Here is a snapshot of what I was watching, at 1844 UTC yesterday, about the predicted time of perihelion. You can see that the position of Comet ISON is in the upper left part of the square the size of the Sun showing where SDO is pointed. The AIA telescopes have a larger field of view, because they need to see the corona around the Sun. So the comet is well inside the AIA images at this time.

There are some movies posted under "Processed Movies" that show the predicted position of Comet ISON along with the frames taken during the perihelion point. Check out ison_171_location_perihelion.mov or ison_171_location_perihelion.mp4. The color table in these movies has been fixed to bring out dim features in the corona. You can watch the corona loops extending out farther into the corona then we would normally see.

To estimate the brightness of the comet we had to assume a composition of the stuff coming off the comet and the density of the corona it was moving through. Even though the comet is heated by the glow of the Sun to sublimate the material, it is the corona that strips off the electrons to create the oxygen ions.

This means we have a couple of things to check as we try to understand the lack of any visible trail in the SDO images. Did Comet ISON have a strange composition? By strange it would have to have very little oxygen. Many molecules that are found in comets have oxygen atoms in them. Water, carbon dioxide, and most rocks have oxygen in them. Comet ISON appeared normal as it moved through the solar system. It may have been running out of ice as it moved into perihelion, but the dust particles should also have sublimated and contributed oxygen to the corona as they flew past.

Perhaps the corona was not as dense as we assumed. The reactions that cause oxygen ions need fast electrons. Each step in the ion chain takes a little time. If the density of the fast electrons is smaller each step takes a little longer. At the same time the oxygen ions are moving away from the orbit of the comet. As the new oxygen ions get further away from the comet their density goes down and they become more difficult to see. This will require us to go look more carefully at those places in the frames where the comet material has been the longest. Maybe a faint signal can be detected.

We have now seen two sungrazing comets in SDO data. The first disappeared before its perihelion and Comet Lovejoy broke up after perihelion and eventually dissipating. We have also looked for at least two others. One never appeared, and now Comet ISON, which appears to have snuck by perihelion without a trace. We will work to understand what happened as Comet ISON, either as a remnant or debris, flew by the Sun.

We are tied at 2 all for sungrzing comets that we saw and didn't see in AIA data. I hope another sungrazing comet comes by soon to break to tie.

18:18 UTC

Image credit: ESA/NASA/SOHO

16:25 UTC

One thing we can be certain of is that ISON's nucleus (if there is one) will be significantly smaller now. Lot of mass will have been lost! (via Karl Battams/NRL/CIOC @ Sungrazer Comets)

16:23 UTC

NASA SDO scientists are still looking at the data to figure out why ISON was not visible on SDO imagery. Updates forthcoming.

15:41 UTC

Comet ISON at 15:41 UTC on November 29, 2013. Image credit: NASA SOHO/SDO

12:30 UTC

ISON appears as a white smear heading up and away from the sun. ISON was not visible during its closest approach to the sun, so many scientists thought it had disintegrated, but images like this one from the ESA/NASA Solar and Heliospheric Observatory suggest that a small nucleus may be intact. Image credit: ESA/NASA/SOHO/GSFC

  • Watch the perihelion LASCO C3 movie here.

08:35 UTC
It's alive!

This is how Comet ISON looks right now:

Image credit: NASA/SOHO/SDO on November 29, 2013 @ 08:35 UTC


06:02 UTC

Video of ISON's perihelion:

YouTube video

03:35 UTC

Schrödinger's Comet

By Karl Battams (NRL/CIOC)

I'll just say this upfront right now: whatever you read in the following blog post, please feel free to assume it is completely incorrect and the truth is actually quite contrary to what I'm saying. It has been – and continues to be – one of those days. 

So this will be a relatively brief blog post because we're up to our necks in media inquiries and attempting to do real science to figure out the mystery that is comet ISON, and Matthew and I are basically the only ones that have abandoned our loved ones on this US national Holiday and continued to work. Here's what we know so far: 

After impressing us yesterday, comet ISON faded dramatically overnight, and left us with a comet with no apparent nucleus in the SOHO/LASCO C2 images. As the comet plunged through the solar atmosphere, and failed to put on a show in the SDO images, we understandably concluded that ISON had succumbed to its passage and died a fiery death. Except it didn't. Well, maybe… 

After perihelion, a very faint smudge of dust appeared in the the LASCO C2 images along ISON's orbit. This surprised us a little, but we have seen puffs of dust from Sungrazer tails, so it didn't surprise us enormously and didn't change our diagnosis. We watched and waited for that dust trail to fade away. Except it didn't. 

Now, in the latest LASCO C3 images, we are seeing something beginning to gradually brighten up again. One could almost be forgiven for thinking that there's a comet in the images! 

Matthew 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… 

I think you get the picture, yes? 

We have a whole new set of unknowns, and this ridiculous, crazy, dynamic and unpredictable object continues to amaze, astound and confuse us to no end. We ask that you please be patient with us for a couple of days as we analyze the data and try to work out what is happening. We realize that everyone now wants to know if it will be visible in the night sky, and how bright it might be. We really hate speculating right now but if someone were to force us into an answer, we would reluctantly say that at least some faint tail remnant should be visible in the coming week or so. But this is highly speculative so please don't take this too seriously just yet. We will absolutely post updated info here as soon as we're more confident, and I will of course continue blogging when I can in the meantime. Just be patient on this and the truth will unfold in time! 

And I just want to end on this note: not long after comet ISON was discovered, it began to raise questions. Throughout this year, as many of you who have followed closely will appreciate, it has continued to confuse and surprise us. For the past few weeks, it has been particularly enigmatic and dynamic, in addition to being visually spectacular. This morning we thought it was dying, and hope was lost as it faded from sight. But like an icy phoenix, it has risen from the solar corona and – for a time at least – shines once more. This has unquestionably been the most extraordinary comet that Matthew and I, and likely many other astronomers, have ever witnessed. The universe is an amazing place and it has just amazed us again. This story isn't over yet, so don't stray too far from your computer for the next couple of days! 

01:30 UTC

That rocky/dusty remnant of Comet ISON seems like it's getting a tad brighter. Well, it looks like Comet ISON is ALIVE!

SOHO's LASCO C3 coronograph from 00:07 UTC on November 29, 2013 (Credit: SOHO/ESA/NASA)

Latest STEREO imagery – ISON look svery alive! (Credit: NASA/STEREO)

November 28, 2013
T -0 D-day! Comet ISON vs The Sun

Comet ISON wll reach its perihelion at 18:44 UTC today.

We've had this cosmic mystery hovering over us since September of last year, and now, at last, we are on the verge of getting an answer. This will not be a scientific discovery that happens behind closed doors, or announced in a stuffy scientific paper that most people won't read. This months-long astronomical cliffhanger is about to reach its conclusion, and will do so live, online, in realtime, for the whole world to see. I hope that everyone appreciates the truly extraordinary nature of this event, regardless of outcome, and I hope that everyone enjoys it as much as us scientists are going to!  – Karl Battams, CIOC. 

21:40 UTC

Sungrazer Comets ‏@SungrazerComets

"It is very possible (probable) that we're just seeing debris from comet #ISON falling apart. I just don't see anything like a nucleus."

21:24 UTC

20:57 UTC

Phil Plait ‏@BadAstronomer

"So, I called the total death a bit prematurely. Something has made it around, but we’ll have to see how much stuff and in what condition." (See image from 19:48 UTC)

20:47 UTC

Some reports say that a tiny bit of ISON did survive the clash.

19:48 UTC

SOHO LASCO C2 view of ISON at 19:48 UTC on Nov. 28. It looks like something made it around the Sun, but it's not ISON as we knew it. Edir: Phil Plait

19:44 UTC

Nothing came up on other side of occulting disc of SOHO's LASCO C2 where ISON should have emerged after perihelion. It is now safe to say that Comet ISON did not survive its close encounter with the Sun.

19:24 UTC

Karl Battams on NASA's hangout: "Let's give it a couple more hours before we pronounce it dead."

19:12 UTC

Click the image to see the video. Image credit: NASA SOHO

19:09 UTC

There is still nothing on SDO images.

18:54 UTC

YouTube video

18:36 UTC

18:20 UTC

Comet ISON has totally evaporate, now it is totally clear:
17:40 UT, STEREO C2: http://www.kommet.cz/datas/users/ison-failed-3_1.png

(you can easily compare with pervious image from 16:18 UT 
http://www.kommet.cz/datas/users/ison-failed_1.png )

Best regards,
Jakub Cerny

  • NASA Hangout – Comet ISON Live

YouTube video

17:54 UTC

17:48 UTC

17:44 UTC

SDO images will kick in anytime now…

16:09 UTC

Here is latest STEREO Ahead image:

Image credit: Stereo Ahead / COR 2

15:42 UTC

Image taken: 15:42 UTC – Image credit: SOHO LASCO C2/SDO AIA 304

15:25 UTC

YouTube video

Video courtesy: CometISONnews

14:45 UTC – CIOC update (by Karl Battams)

There is only a few hours until perihelion, and anything could happen. ISON may have been outbursting in the LASCO field of view, and a rocky nucleus could still exist at the center of all that. If there is still something solid there, and it reaches perihelion, then even if it falls apart at that point, we will still seesomething emerge from the solar atmosphere. And even if the comet does get completely destroyed in the next few hours, I hope that we will get a spectacular show in the SDO images. I also want to note that we are analyzing the SOHO data very carefully and we do see some evidence that maybe ISON's gas production is completely finished but dust production is continuing at a steady rate. Indeed Matthew just said to me, "I have never seen light-curve behavior like this! It's doing completely different things in the different color filters! 

He has looked at well over 1,000 sungrazing comets, so when he says a comet is weird… it's weird! So the bottom line is that we have contradictory evidence and we're still trying to interpret it. There is hope for comet ISON! 

Regardless of what unfolds today, please remember this: we're watching a truly unique astronomical event for which we have no similar occurrence on record, and we're getting to watch it unfold live on the internet. That's worth restating: this is one of the more extraordinary astronomical events to happen in modern history, and we get to sit in our comfy chairs and watch a giant ball of 4.5 billion year old ice hurtle through the Sun's million-degree outer atmosphere at 0.1% of the speed of light, 93-million miles away from us. Regardless of sizzle, fizzle, or a victorious reemergence, comet ISON's perihelion is a truly spectacular event! (Source)

14:30 UTC

14:24 UTC

13:19 UTC

Bad news: the very latest images show that #ISON is considerably fainter… via SungrazerComets

ISON entered LASCO C2 field of view:

13:10 UTC

SOHO satellite just came back into contact after 3 hr gap. Images are expected soon.

09:18 UTC

Latest SOHO images stopped coming in.

Image credit: NASA SOHO

Comet ISON is having its historic close encounter with the Sun today and it is going live. Yesterday, ISON climbed tremendously in brightness but this can't offer us any evidence at all as to whether it will survive or not. 

General consensus is that ISON is behaving like a sungrazer. "It means that ISON is now in a very near-Sun region of the solar system and is experiencing levels of solar radiation that your average comet is never going to have to deal with. Accordingly, its surface is boiling away furiously, releasing tremendous amounts of ice, dust and gas and brightening up enormously." – Karl Battams, CIOC. 

If ISON does survive, it will probably become visible to experienced amateur astronomers by December 2 or 3.


Live events today

  • Links and timetable for real-time images and videos from space-based solar observatories —>>> here.
  • From 18:00 – 20:30 UTC – NASA's will host Google+ Hangout "Fire vs. Ison" for live coverage of perihelion and the comet's potential breakup.
  • "Comet ISON perihelion party" thread is in progress on Reddit here.

Twitter channels with frequent updates:



November 27, 2013
T -1 Brightening dramatically

Latest CIOC update with LASCO C3 imagery :

Now that we have observations of the comet in the NASA STEREO instruments and, more recently, the ESA/NASA SOHO LASCO C3 instrument, CIOC team member Matthew Knight has been able to start recording photometry of the comet. His results seem to imply that the comet may have experienced an outburst during the (approximate) period Nov 21 – 23 with corresponding brightness increase, followed by a leveling off and then dropping back down to "pre-outburst" levels. Since entering the LASCO C3 field of view, comet ISON has increased by at least a factor of four, and indications are it may be closer to a factor of ten. In the most recently available images, the comet appears to be around magnitude +0.5

It is now the opinion of the CIOC Team that Comet ISON is now behaving like a sungrazing comet. We can not comment on whether the nucleus is in tact or not, but our analyses indicate that its rate of brightening is directly in line with that we have experienced with other sungrazing comets. This has no implication on its chances of survival. We strongly encourage all professional solar observatories who have plans in place for observing the comet, to please do so, and the teams should plan for an object brighter than negative one magnitude (and we are being conservative on this estimate). 

Today's tl;dr is somewhat upbeat: we don't know if ISON will survive, and we won't know until it either does it or vaporizes. But the comet is still "alive" and brightening dramatically in accordance with the behavior we expect of sungrazers. Professional observers with solar telescopes should plan for a negative magnitude object, and we urge observation from these facilities. 

CRITICALLY IMPORTANT: Comet ISON is extremely close to the Sun and you should NOT attempt to observe it in binoculars or telescope unless you are highly experienced in making these observations. Sunlight through magnifying optics can and WILL permanently damage eyesight. 

Image credit: NASA SOHO 

ISON entered SOHO Lasco C3 early on November 27 and first images are already here. A solar flare and CME decided to join on the image below:

Image credit: NASA SOHO

The source of the cloud is a farside active region, which is not directly facing the comet.

You can watch ISON's passage and perihelion on space-based solar observatories now. Find all the links and timetable here.

November 26, 2013
T -2

Comet ISON entered the STEREO Behind spacecraft COR-2 field of view and is now clearly visible in the left corner of the latest STEREO-B coronagraph imagery. Also, it is visible on STEREO Ahead HI1.

Comet ISON seen on STEREO-B COR2 image from 15:40 UTC on November 26, 2013 (Credit: NASA/ISTEREO)

In the meantime, Jakub Černý posted this today:

No good news from STEREO-A. Matthew Knight has sent me his photometry of spacecraft images to 15UT 25. Nov. They well corresponds to latest visual observations. After strong fade, comet has started to gaining brightness again. Unfortunately with speed far bellow (n=0.66) brightening for simple reflecting body (n=2). If we assume that all brightness coming from dust cloud, there is nothing inside coma that can resupply dust to coma at least on same level. What is worst, deviation from average activity level keep growing. Such characteristic more corresponds to slowly scattering dust cloud, then intact comet.


Best regards,
Jakub Cerny

Astronomers using the IRAM millimeter telescope in Spain are reporting consistent, rapid fading of the molecular emission lines between November 21 and November 25 by at least a factor of 20. According to Michal Drahus of Caltech, this may indicate that the nucleus is now at best marginally active or that it no longer exists.

According to astronomer Karl Battams of NASA's Comet ISON Observing Campaign, this fading emission lines could indicate that the nucleus has completely disrupted, releasing an enormous volume of dust while significantly reducing emission rates. 

However, recent STEREO A HI1 images show Comet ISON looking pretty intact:

STEREO A HI1 image taken at 12:49 UTC on November 26, 2013 (Credit: NASA/STEREO)

Matthew Knight (Lowell Obs.) measured the comet with the STEREO A spacecraft's HI-1 instrument:

ISON has continued to brighten in the STEREO-HI1A images over the last 36 hr. As of Nov 26.54 it is approximately a V magnitude of 3.9 in an 11.7 arcmin diameter aperture. Just looking at the lightcurve by eye suggests that there may have been an outburst from roughly Nov 20-22 which was superposed on a steadily brightening curve.

November 25, 2013
T-3 – Molecular emission dramatically fallen

Latest update from CIOC: "We are seeing reports online that molecular emission from the comet has fallen dramatically, meanwhile dust production seems to be enormous. What this could indicate is that the nucleus has completely disrupted, releasing an enormous volume of dust while significantly reducing emission rates. Fragmentation or disruption of the nucleus has always been the highest risk factor for this comet so if this has indeed happened then while unfortunate, it would not be a surprise. 

However, these reports are new, and while they are undoubtedly valid, we do still need to keep observing the comet to be sure what it happening. Remember: Comet ISON is a dynamically new sungrazing comet, fresh in from the Oort Cloud, and the last time we saw an object like this was never! Furthermore, a sungrazing comet just three days from perihelion has never been studied in this kind of detail – we're breaking new ground here! When we factor in your standard "comets are unpredictable" disclaimer, what we have is a huge recipe for the unknown." 

Read more.

YouTube video

 The latest movie from the STEREO-A spacecraft's Heliospheric Imager shows the comet over a five-day period from November 20 to November 25, 2013. (Credit: NASA/STEREO)

Comet ISON is expected to pass through the Sun's atmosphere at just about 1.2 million km (730 000 miles) above the solar surface on November 28, 2013 at 18:44 UTC.

Space-based solar observatories phase

Comet ISON is now entering the fields of view of space-based solar observatories and 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.

Both STEREO spacecraft will have a view of the comet in the COR1 and COR2 coronagraphs in the hours around closest approach on November 28.

The coronagraphs on STEREO Ahead will be able to see the comet for about a day and half between about 04:00 UTC on November 28, and 13:00 UTC on November 29. The Behind coronagraphs will have a longer look at the comet, from about 06:00 UTC on November 26 until the end of the day on November 29. During the period when Comet ISON is closest to the Sun, it will actually pass in front of the Sun as seen from Behind.

STEREO-A will be the only one that sees the comet transit across the face of the Sun.

Image credit: NASA SDO. Edit: The Watchers

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.

SDO spacecraft will off-point at three different positions as Comet ISON moves through perihelion. This website will display near realtime images and movies. Images should begin appearing sometime between 17:44 and 18:00 UTC (12:45 pm and 1:00 pm ET). The Sun will appear in the upper right corner of the images and Comet ISON will move through the images from the lower right to the upper left.

SDO home page will have images from four of the AIA wavelengths during each the views (off points), Approach, Perihelion, and Departure. These wavelengths were chosen because in December 2011, when Comet Lovejoy passed perihelion, it was very bright in these wavelengths, and they believe they are the best choice for Comet ISON. We will not see a normal comet tail. The glowing material is forced to move along the Sun's magnetic field. It will look like a cloud moving along and away from the orbit of the comet.​

From SOHO's viewpoint the comet enters from the lower right early on November 27 and exits towards the top near the end of November 30.

Solar wind buffeting ISON and Encke

Image credit: NASA/STEREO

Click on the image for November 21 – 23 animation. Image credit: NASA/STEREO

November 24, 2013

ISON continues its journey towards the Sun, and it appears to still be in one piece. Ground based observations are now almost impossible, and we've entered the realm of solar spacecraft observing.

The next few days are where the fun really begins. (CIOC – Present)

November 23, 2013

Five more days from ISON's perihelion. ISON is now clearly visible on STEREO Ahead HI1 images.

Comet ISON on November 23, 2013 (Credit: NASA/STEREO)

C/2012 S1 (ISON) is now 45 million km away from the Sun and 129 million km (80 million miles) away from Earth.

Location of Comet ISON on November 23, 2013 (Credit: Solar System Scope; Captions: The Watchers)

Daylight Comet ISON, Los Angeles (USA)

Taken by Vince on November 23, 2013 @ Los Angeles, CA via SpaceWeather

November 22, 2013 

Comet ISON is now only six days from it's perihelion. According to an estimate by astronomists Jean-François Soulier and Alain Maury, ISON is still 4th magnitude. There are no changes in structure of the comet or it's tail. ISON is becoming much harder to detect as it gets lower at the horizon every day.  Fritz Helmut Hemmerich took this great image from Tenerife, Canary Island:

Comet ISON imaged from Canary Islands (Credit: Fritz Helmut Hemmerich via SpaceWeather)

Comet ISON above the French riviera (Nice)

Taken by MANU ANTUNA on November 22, 2013 @ COL DE VENCE – FRANCE – via SpaceWeather

November 21, 2013

Comet ISON enters STEREO Ahead HI1 field of view.

ISON can be seen in these images along with Earth, Mercury and Comet 2P/Encke. The tails streaking out from behind both comets can be seen moving along with the steady stream of particles – called the solar wind – that flows out from the Sun. Image credit: Karl Battams/NASA/STEREO/CIOC.

Comet ISON seen in the lower left corner of STEREO Ahead HI1 image. First entry was recorded at 21:34 UTC on November 20, 2013. (Credit: STEREO/NASA)

Because Comet ISON is seen only early in dawn, it will soon be impossible for cameras on Earth to track it. Juan Carlos Casado photographed the comet over the Teide Observatory in the Canary Islands at the dawn of November 21, 2013:

Comet ISON seen from Gran Canary at dawn of November 21, 2013. Lower left is Mercury. (Credit: Juan Carlos Casada via SpaceWeather)

This morning several astronomers recorded a tail disconnection event — a blob of the ion (gas) tail being pinched off by a gust of the magnetic-field-bearing solar wind, and blowing downstream. 

November 20, 2013

Only 8 days to perihelion. Astronomers are getting more and more exciting as Comet ISON approaches the Sun. Early today ISON was positioned roughly between the bright star Spica and the planet Mercury. Now is the right time if you wish to see Comet ISON with naked eye because It’s appearing much lower each morning as it approaches the Sun.

Orbital elements and sky map for Comet ISON on November 20, 2013 (Credit: Solar System Scope/MPC)

Start looking an hour before your local sunrise and continue as dawn grows brighter. The planets Mercury and Saturn and the star Spica help to point the way.

Vitali Nevski, ISON's co-discoverer, estimated its brightness at magnitude 3.7 this morning in Russia. John Bortle in New York State calls it 4.5 but was nevertheless struck by its new brilliance. 

New image of Comet ISON taken early on November 20, 2013 by Vitali Nevski (Credit: Vitali Nevski via SpaceWeather.com)

“We might witness a nice, long-tailed comet visible to the naked eye that will leave millions of people with fond memories for a lifetime, or maybe it will be a small comet for sky hunters using binoculars and a good map of its position. Or it might yet break up and vanish.”  Alan MacRobert, senior editor of Sky & Telescope magazine

In the meantime, the FORTIS payload was successfully launched this morning to observe Comet ISON.  Launched on a Black Brant IX sounding rocket, the payload flew to an altitude of 172 miles before descending via parachute at White Sands.  Preliminary reports show that good data was obtained and the mission was a success.  Payload recovery is in progress.

November 19, 2013
Another outburst

The scientists using the European Southern Observatory's TRAPPIST telescope are this morning reporting that comet ISON is again in outburst!

Overnight they have seen a six-times increase in production rates (gases, water). This is not as large as the outburst last week that saw a ten-or-more-fold increase in production, but this is still a very significant outburst. They note that they are just about at the end of their observing run but will continue to follow up as much as they can.

There had been reports of "coma wings" in processed images of the comet, and these are a feature that has been associated with fragmentation of comet nuclei. We blogged about this yesterday with the main conclusion being that yes it certainly could mean fragmentation, but also could mean one of several other things that have nothing to do with fragmentation. Thus we urged continued imaging and community-wide discussion of this feature. Overnight we have heard that those "coma wing" features appear to have faded. Does this mean ISON has definitely not fragmented? No, but it lends weight to the belief that it's still in one piece. (Source: CIOC – Present)

Observing conditions are becoming extremely difficult, and very few pre-perihelion days remain for useful ground-based observations.

The latest light-curve for Comet ISON (compiled November 19, 2013 by Matthew Knight)

CIOC released new updated light curve image by Matthew Knight. The post-outburst observations are very evident but note that there are no new observations that include the second outburst. It will be a day or so before that information comes in. Furthermore, data points are going to be scarce now for all the reasons we just highlighted about how difficult ISON is becoming to observe.

In the meantime, FORTIS rocket launch to observe Comet ISON has been rescheduled for the morning of November 20 because of a payload issue. FORTIS will join a world-wide contingent of observatories trying to understand this early bit of our solar system's history.

November 18, 2013
10 days to perihelion

Comet ISON is now 74 million km away from the Sun and 129 million km away from the Earth. It's closest approach to the Sun is on November 28, 2013 at 18:44 UTC.

Comet ISOn seen near bright Spica on November 18, 2013 from Manila, Philippines (Credit: JV Noriega)

It is still unclear what exploded from the ISON's core on November 14th but it created a spectacularly-long tail which is now more than 16 million kilometers. Take a look at its image taken by Michael Jäger on November 17th at SpaceWeather.

The animation below consists of 8 images, each a 3-image median combine stack, all with a r' filter, from 11:43 to 12:53 UTC, November 14, made by Bruce Gary using a Celestron 11-inch telescope. Filamentary structure can be seen moving away from the sun at high speed. The motion of jets that can be seen first on the side is backwards and toward the center of the tail.

Animation credit: Bruce Gary

November 16, 2013

According to some observers ISON is 10 times brighter today than it was on November 13th, prior to its outburst, and its tail extends more than 8 million kilometers.

Because of so much gas and dust spewing from its core it is impossible to see what caused the outburst on November 14th but one possibility is that nucleus has completely fragmented.

German amateur astronomer Waldemar Skorupa recorded this image from Kahler Asten, in Germany, on November 16, 2013. (Credit: Waldemar Skorupa via spaceweather.com)

"If so, it will still be several days before we know for sure," says Karl Battams, an astronomer with NASA's Comet ISON Observing Campaign. "When comet nuclei fall apart, it’s not like a shrapnel-laden explosion. Instead, the chunks slowly drift apart at slightly different speeds. Given that ISON’s nucleus is shrouded in such a tremendous volume of light-scattering dust and gas right now, it will be almost impossible to determine this for at least a few days and perhaps not until the comet reaches the field of view of NASA's STEREO HI-1A instrument on November 21, 2013. We will have to wait for the chunks to drift apart a sufficient distance, assuming they don't crumble first."

November 15, 2013

Outburst continues and today's images reveal multiple streams. Damian Peach captured this awesome image of ISON today:

Image copyright: Damian Peach. November 15, 2013

Comet ISON taken by James Foster on November 15, 2013 from Chuchupate, Lockwood Valley, California (Credit: James Foster via SpaceWeather.com)

The TRAPPIST national telescope at ESO's La Silla Observatory obtained new image on the morning of November 15, 2013. TRAPPIST has been monitoring comet ISON since mid-October, using broad-band filters like those used in this image. It has also been using special narrow-band filters which isolate the emission of various gases, allowing astronomers to count how many molecules of each type are released by the comet.

Comet ISON outburst seen on November 15, 2013 (Credit: TRAPPIST/ESO)

November 14, 2013
First outburst

Observers around the world are reporting that Comet ISON brightened sharply last night and is now at the threshold of naked-eye visibility. By some reports, ISON surged in brightness by approximately 2 magnitudes over last 24 hours and is now brighter than comet Lovejoy.

If this trend continues, it will be a faint but easy naked-eye object by the end of the week, SpaceWeather reports.

  • Read more about it here.

Meanwhile, Solar System Scope team have added a second view at their 3D model of ISON's approach. Now you can switch to "View from Earth" and see the position of ISON in your night sky.

The link to the updated 3D model is here www.solarsystemscope.com/ison

  • If you'd like to share your images of ISON with us send them via this form. Be sure to include description with date taken and your name. You can include a link to your website or gallery, Flickr/Facebook/Twitter/…/ profile, copyright notice or any text you'd like to go with the image. You can also contact us with the link to the image.

November 13, 2013

Fifteen days from perihelion, Comet ISON is brightening fast, is interacting with the solar wind, and appears to be undergoing an outburst. Reported magnitudes are of the order of +8 to +7, making ISON visible to most people in binoculars. The nucleus is still intact. However, noticeable brightening and increased rates of dust and gas production are being reported. 

Comet ISON on November 13, 2013 taken by Gregg Ruppel from Ellisville, MO, USA (Credit: Gregg Ruppel via SpaceWeather.com)

November 11, 2013

Comet C/2012 S1 (ISON) is now inside the orbit of Venus, and has only seventeen days left before it reaches its closest point to the Sun, on November 28, 2013. But Comet ISON is moving extremely fast now at around 50 km/s (180 000 km/h, 112 000 mph), and will soon become increasingly difficult to observe as it approaches twilight skies.

The latest light-curve for Comet ISON (compiled November 11, 2013 by Matthew Knight).

Comet ISON taken by Ernesto Guido, Nick Howes, Martino Nicolini on November 10, 2013 with the 2-meter Liverpool Telescope (Credit: Remanzacco Observatory/Guido/Howes/Nicolini)

November 10, 2013

Double tail feature is now visible. Michael Jäger took this image of ISON on November 10, 2013. One tail is the ion tail. It is a thin streamer of ionized gas pushed away from the comet by solar wind. The filamentary ion tail points almost directly away from the sun. The other tail is the dust tail

Taken by Michael Jäger on November 10, 2013 @ Jauerling Austria (Image credit Michael Jäger via SpaceWeather's Real-Time ISON gallery

November 9, 2013

Multiple observers now report that Comet ISON could be seen by binoculars and backyard opticsComet ISON is currently moving through the constellation Virgo low in the eastern sky before dawn. It is still too dim for naked eye.

November 8, 2013

ISON is passing through the equinoctial point in Virgo around 20:00 UTC, passing into the southern celestial hemisphere and south of the ecliptic.

Comet ISON captured by astronomer Richard Dynes on November 8, 2013 using a C8 on a CGEM mount Canon 60Da camera and CLS filter from Arizona, US (Credit: Richard Dynes via SpaceWeather gallery)

November 7, 2013

Comet ISON is now inside the orbit of Earth and racing toward the Sun. Last night, astronomer Alberto Quijano Vodniza of Pasto, Colombia, recorded the comet moving through space at 165 762 km/h (103 000 mph / 46 km/s). Click here to see the animation.

Currently, Comet ISON is passing less than a degree from the +3.6 magnitude star Zavijava (Beta Virginis).

November 6, 2013

New image by Damian Peach shows some interesting activity within ISON's tail.

Comet ISON on November 6, 2013 (Credit: Damian Peach)

November 5, 2013

Casey Lisse of the Comet ISON Observing campaign (CIOC) reports that the Chandra X-ray Observatory just became the 9th spacecraft to image the comet. So far, eight spacecrafts have observed Comet ISON – SOHO, STEREO A, STEREO B, Spitzer, Deep Impact/Epoxi, Swift, Hubble and MRO. More observation attempts are expected from the ESA Venus Express and Proba-2 satellites, MESSENGER and the NASA Solar Dynamics Observatory.

Currently, Comet ISON is crossing the border from the astronomical constellation of Leo into Virgo.

October 30, 2013

Today, ISON is about 190 million km away from Earth traveling at speed of about 49.01 km/s relative to Earth. Its closest approach to Sun is in 28 days and 20 hours. This image was taken by Damian Peach on October 24th:

Comet ISON on October 24th, 2013. Image copyright: Damian Peach.  0.11m F5.6. STL-11k camera. LRGB: L: 6x3mins. RGB: 1x2mins. With Messier 95.

Check out his other images of our Solar System too. He has more ISON images here.

For better perspective on ISON's location and approach check this 3D model by Solar System Scope.

October 27, 2013

Justin Ng from Singapore used a telescope and special camera to create excellent time-lapse video of Comet ISON on October 27, 2013. 

October 25, 2013

In the early morning of October 25, 2013 NASA's Marshall Space Flight Center in Alabama, US used a 14" telescope to capture image of Comet C/2012 S1 (ISON), which is brightening as it approaches the Sun. The comet shines with a faint green color just to the left of center. The diagonal streak right of center was caused by the Italian SkyMed-2 satellite passing though the field of view.

Comet ISON on October 25, 2013 (Credit: NASA/MSFC/Aaron Kingery)

Comet ISON is still too faint for the unaided eye or small binoculars, but at magnitude 8.5 it's now an easy target in a small telescope.

October 17, 2013

Officials with the Space Telescope Science Institute in Baltimore, which operates Hubble, wrote in a statement that in NASA Hubble Space Telescope image taken on October 9, 2013 the comet's solid nucleus is unresolved because it is so small.  If the nucleus broke apart then Hubble would have likely seen evidence for multiple fragments according to statement.

The coma or head surrounding the comet's nucleus is symmetric and smooth, which would probably not be the case if clusters of smaller fragments were flying along. What's more, a polar jet of dust first seen in Hubble images taken in April is no longer visible and may have turned off.

A recent study reported that with a nucleus estimated to be between 0.12 miles and 1.2 miles across (0.2 to 2 km), the comet appears to be big enough to avoid destruction by the sun's heat.

Comet Ison taken on October 17, 2013 from San Marcello, Italy (Credit: Bacci/Tesi/Fagiolo/GAMP-via SpaceWeather ISON gallery)

Currently, Comet ISON is 153 million miles (247 million km) away from Earth.

October 10, 2013

Researchers Kevin Walsh and Mathew Knight place the size of ISON’s nucleus in the range of 0.5 to 2 kilometres. Comet nuclei smaller than 200 metres in diameter, with an average density or lower typically do not survive a close passage to the Sun. So it looks this is encouraging news for ISON when it comes to surviving perihelion.

October 9, 2013

Comet ISON is inside Mars’ orbit and about 177 million miles from Earth. NASA's Hubble Space Telescope took photo of  ISON and it appears the nucleus of ISON is intact.

NASA's Hubble Space Telescope took this photo of Comet ISON inside Mars' orbit on October 9, 2013 (Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA))

Meanwhile, new studies released at the American Astronomical Society’s 45th Annual Division for Planetary Sciences meeting in Denver suggests that ISON just could make it through its close perihelion passage near the Sun. Comet ISON is expected to be the most active and put on its best showing post-perihelion – if it survives. 

The rotational pole of the nucleus indicates that only one side of the comet is being heating by the Sun on its way in until approximately one week before it reaches its closest point to the Sun. Research scientist Jian-Yang Li of the Planetary Science Institute noted that the reddish color of the coma of ISON suggests an already active comet sublimating water ice grains as they move away from the nucleus. Read more

October 6, 2013

Astronomer Efrain Morales Rivera captured approaching Comet ISON from Jaicoa Observatory in Aguadilla, Puerto Rico.

Comet ISON as imaged from Aguadilla, Puerto Rico recently on October 6th. (Credit: Efrain Morales Rivera)

October 5, 2013

Great images of ISON are now being taken by astronomers around the world. Michael Jäger from Austria, observed ISON on October 5 and combined multiple exposures through red, green, blue, ultraviolet and infrared filters to found out that it was green:

Photo by Michael Jäger / http://cometpieces-at.webnode.at/

ISON's green color comes from the gases surrounding its icy nucleus. Check more images at SpaceWeather's real-time ISON image gallery.

October 3, 2013

It seems Bruce Gary, Ignacio Ferrin and those who said ISON will not be what everybody hoped it would be were right. As it passed Mars ISON is still faint and Ferrin believes it is about to disintegrate. The light curve of ISON, he argues, resembles the light curves of other comets that have have fallen apart. However, many experts still believe the comet is on track to become a bright sungrazer in late November.

October 2, 2013

New images were released today from the High Resolution Imaging Science Experiment (HiRISE) camera on board the Mars Reconnaissance Orbiter (MRO). On September 29, 2013 MRO maneuvered to point its HiRISE camera at ISON. This is what it recorded on September 30th:

Image of Comet ISON acquired on September 30, 2013 with the HiRISE camera on NASA’s Mars Reconnaissance Orbiter. This is a preliminary single (non-stacked) image, and appears fuzzy in part because it still contains noise and background stars.

HiRISE saw a small spot at the position of ISON that is relatively bright, like a star, but moving relative to actual stars. The comet's coma is apparently very faint, so these data provide useful constraints on the size of the comet nucleus and its overall brightness, key measurements to understand its behavior and useful knowledge to subsequent observers. 


These images show a 256 x 256 pixel patch of sky at the range to the comet of 8 million miles and when the solar phase angle is 47 degrees. Three more observations of ISON were planned for 1 and 2 October as the comet moves through closest approach to Mars at 7 million miles, but with less illumination as seen from Mars. 

Based on preliminary analysis of the data, the comet appears to be at the low end of the range of brightness predictions for the observation. As a result, the image isn't visually pleasing but low coma activity is best for constraining the size of the nucleus. This image has a scale of approximately 8 miles (13.3 km) per pixel, larger than the comet, but the size of the nucleus can be estimated based on the typical brightness of other comet nuclei. The comet, like Mars, is currently 241 million kilometers from the Sun. As the comet gets closer to the sun, its brightness will increase to Earth-based observers and the comet may also become intrinsically brighter as the stronger sunlight volatilizes the comet's ices. HiRISE

October 1, 2013

ISON flew by Mars today and images from the HiRISE camera of NASA’s Mars Reconnaissance Orbiter should be available within the next couple of days. That is, if they manage to resolve government funding because as of today, due to government shutdown, only essential NASA personnel is allowed to work. NASA's homepage is unavailable and none of its websites is being updated. Out of their 18 000 employees, only 600 will be allowed to work. Those 600 are the support to the International Space Station, other missions currently in operation off the surface of planet Earth, and critical operations at each site. That, apparently, includes Mars missions who were supposed to take pictures today.

Hopefully, ESA's Mars Express will have something for us very soon.

3D model of ISON's approach by Solar System Scope gives us a good idea where ISON is today. Scroll down the article for animated 3D model.

ISON's location on October 1, 2013. Image credit: Solar System Scope

September 29, 2013

ISON is approaching Mars for a 0.07 AU (10.5 million km) close encounter on October 1st. Mars satellites and rovers will have a close-up view.

Using a remotely controlled 14-inch telescope in New Mexico, Rolando Ligustri photographed ISON approaching Mars on September 28th:

Image credit: Rolando Ligustri

The following NASA video details Mars fly by:

YouTube video

September 28, 2013

A sub-orbital balloon was launched to study ISON from above nearly all of the Earth's atmosphere. The Balloon Rapid Response for ISON or BRRISON, is built and managed for NASA by The Johns Hopkins University Applied Physics Laboratory. The baloon will also observe other science targets.

BRISSON is carrying a 0.8 m telescope and optical and infrared sensors to study the comet. It will observe Comet ISON in the near-infrared and in the near-ultraviolet and visible wavelength ranges at an altitude of 36 km (120 000 feet).

The near infrared camera will measure the ratio of carbon dioxide (CO2) to water (H2O) emissions from the cometary nuclei as a vital diagnostic of the comet’s origins. These are unique observations that cannot be obtained by any other means. The near ultraviolet and visible camera will observe at the wavelength of the hydroxyl (OH) emission from Comet ISON and will test and characterize the effects of atmospheric turbulence on optical observations at balloon altitudes.

Update, October 29, 2013:

BRRISON suffers science payload anomaly, unable to collect data

FORT SUMNER, N.M.—The Balloon Rapid Response for ISON (BRRISON) payload suffered an anomaly following launch Sept. 28 from the Columbia Scientific Balloon Facility in Fort Sumner, N.M., preventing the payload from collecting mission data.

Approximately two and a half hours after BRRISON’s launch, the 0.8-meter telescope on the gondola returned to a stowed position too rapidly, driving the telescope past a stow latch. The telescope was unable to be redeployed despite numerous attempts by the BRRISON team from the Johns Hopkins University Applied Physics Laboratory, which built BRRISON for NASA. 

An Interim Response Team will assess the BRRISON payload during recovery operations later today.

BRRISON was launched to study the rare sun-grazing Oort Cloud Comet ISON and other objects with both infrared and ultraviolet/visible light instruments. (Source)

September 25, 2013

Today, Comet ISON is 345 million kilometers away from Earth traveling at speed of 31.90 km/s. Throughout September ISON's average speed was 109 366 km/h or 67 957 mph.

It is about as bright as a 14th magnitude star, which is not as bright as some astronomers expected. Nevertheless, according to several experts Comet ISON is still on track to become an impressive sungrazer. John Bortle predicts ISON will rival Venus during the hours leading up to its closest approach to the Sun in November, while Matthew Knight notes that Comet ISON is brighter than Comet Lovejoy was at the same distance from the sun in 2011.

On the other hand, Bruce Gary noticed fading which he described as "unphysical". Though he says he is an amateur on comet matters he has a very impressive analysis on his website.

This is what he has to say about it:

Measurements on several dates (after reappearing from behind the sun) show that the comet is brightening at a lower rate than expected, as if the activity level on the nucleus surface is actually decreasing! ISON has probably passed the "frost line" so why isn't it brightening instead of fading with respect to a model?  I've begun to lose interest in this comet, which may never become visible to the unaided eye. I wonder why someone ever suggested that it could become "comet of the century"? ​

Check out SpaceWeather's image gallery for latest images of Comet ISON.

September 24, 2013

Slooh.com’s Canary Islands Observatory captured asteroid 433 Eros seeming to fly with Comet ISON on September 24th, 2013. This 2nd largest near-Earth asteroid — which has been visited by the NEAR probe — is traveling faster, along a different orbit.

YouTube video

September 23, 2013

Comet ISON is still more than two months away from its spectacular close encounter with the Sun. Already, the comet has become a good target for backyard telescopes in the pre-dawn sky.

YouTube video

September 17, 2013

ISON is 383 million kilometers away from Earth traveling at a speed of 30.66 km/s (110 376 km/h) as it approaches Mars. It has long passed Jupiter and will flyby Red Planet on October 1, 2013, at about 17:24 UTC. It will continue to accelerate steadily until November 28 when it is expected to whip around the Sun at an astonishing speed of 1 359 896 km/h (845 000 mph).

Early indications from students who have been processing data from NASA’s Swift satellite, estimate the comet to be around 4.82 km (3 miles) in diameter. They have reached this conclusion by observing the amount of ice and dust emitted from ISON’s surface as it falls through space toward the Sun.

Armada of ground based amateur astronomers and an unprecedented space fleet is tracking and waiting for ISON as it moves through our Solar System to meet the Sun on November 28, 2013. It is however, still to early to make final forecast as to what will happen to it. If ISON survives the Sun, it will deserve to be called "the comet of the century" because in that case it might emerge so bright it will become visible on Earth even in daylight. It is still a big IF, so November 28 is the day when we will know exactly.

Comet ISON flying toward the Sun, ​383 million kilometers away from Earth. ​Dennis Whitmer obtained 40 useful images of ISON on the morning of September 15, 2013. Then Bruce Gary used some of those images to create this GIF animation. Image credit: Dennis Whitmer/Bruce Gary

Comet ISON’s path through the constellations of Gemini, Cancer and Leo up until the end of October when ISON will be well on its way to perihelion due to occur on November 28, 2013. Image credit: NASA’s Goddard Space Flight Center

August 12, 2013

For several weeks now, ground-based observers have been blind to Comet ISON as our local star was sitting directly between us and the comet. 

On August 12 ​Bruce Garry broke the silence and anticipation when he took first images after ISON emerged from solar conjunction.

Image credit: Bruce Gary

June 13, 2013

NASA's Spitzer Space Telescope observed Comet ISON at 310 million miles away from the Sun.

Comet ISON as seen by Spitzer on August 12, 2013. Image credit: NASA/Spitzer

Read about their results here.

May, 2013

HST observed the comet on May 2 and May 7, and produced an upper limit on how fast the comet was producing carbon monoxide. Hubble released a movie of the comet from May 8, 2013: http://1.usa.gov/17RuUS1

April 30, 2013

Image credit: Hubble Space Telescope

NASA’s Hubble Space Telescope observed Comet ISON at 621 million km or 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 4.8 – 6.4 km (3 to 4 miles) across. Since the comet was so bright and active, scientists had assumed the nucleus was larger.

Hubble found the dusty coma, or head of the comet, to be around 4 850 km (3 100 miles) across and the tail to be more than 92 000 km (57 000 miles) long. 

Read more about it here.

January – March, 2013

The Ultraviolet/Optical Telescope aboard NASA's Swift imaged comet ISON (center) on Jan. 30, when it was located about 3.3 degrees from the bright star Castor in the constellation Gemini. At the time of this 5.5-minute optical exposure, ISON was about 5,000 times fainter than the limit of human vision. Image credit: NASA/Swift/D. Bodewits, UMCP

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.

January 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.

YouTube video

This series of images of comet C/2012 S1 (ISON) was taken by the Medium-Resolution Imager of NASA's Deep Impact spacecraft over a 36-hour period on January 17 and 18, 2013.

September 24, 2013

By September 24, 2012, Comet ISON had received an official designation of C/2012 S1 (ISON), and a preliminary orbit determination that brought it rather close to the Sun in November of 2013.

September 21, 2012

Comet ISON was first discovered by Russian astronomers, Vitali Nevski and Artyom Novichonok, using a 16-inch telescope that is part of the International Scientific Optical Network (“ISON”), and after which the comet was named.

Within a couple of days of Novichonok and Nevski reporting their find, other observatories had successfully located the comet, including in some images that actually predated the discovery date by over nine months.

Featured image: Damian Peach


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