[X] My Assistant

[Mongo]

posted by Erik Bryssinck at 1:43 this morning:

Re: Dramatic fading of ISON's molecular emission lines

Hello,

Just for the record, we (CARA-project) are revisiting our Af(rho) data of the last days. Possible is here seen a problem with the data/image processing and it could be that the last Af(rho) is about a factor 4x lower. The SNR is not so good of the CCD-images also the gradient in the images is pretty high. This give more uncertainties and introduces increasing errors . We are checking now our procedures and more indepenent checks are needed. I hope we can clear this out in the next day('s).
__________________________________

kind regards,

Erik Bryssinck

This would be good news if a significantly lower Af(rho) is confirmed. A very high Af(rho) indicates a massive dust release, possibly indicating a breakup event. So if the actual Af(rho) is only a quarter of the initially reported value, the disruption event is smaller or even non-existent.

posted by Jakub Černý at 6:01 this morning:

No good news for ISON

Hi all

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.

http://www.kommet.cz/datas/users/ison-lc-perv2_1.png

Best regards,
Jakub Cerny

posted by filipfratev at 8:35 this morning:

RE: No good news for ISON

Hi Jakup,

Let's to wait for the new set of STEREO photometry including up to 26.5-27.5/11/2013. There is a clear difference from 25.5: http://stereo-ssc.nascom.nasa.gov/browse/2...51801_s7h1A.jpg to 26.4: http://stereo-ssc.nascom.nasa.gov/browse/2...91801_s7h1A.jpg

I hope that the comet is on the "good line"now. Moreover you can see this: http://stereo-ssc.nascom.nasa.gov/browse/2...93924_d7c2B.jpg and after 2h UT this night we can expect to have access to the SOHO images. For me the comet looks still intact.

Regards,
Filip

There is a huge difference of opinion here. We will need to wait for more data, to see which post better describes the current activity level of ISON.

[Mongo]

Sungrazer Comets @SungrazerComets 2m

Hot off the press from Kitt Peak: Matthew Knight sees a nice steady increase in #ISON's brightness since yesterday.

Sungrazer Comets @SungrazerComets 1m

Quote from Matthew: "Since yesterday, #ISON has been behaving nicely!" Latest data is only 5hrs old! #CIOC

******

Who is Matthew Knight? From the ISON Campaign website:

Matthew Knight (Lowell Observatory, Flagstaff, AZ) is an astronomer specializing in comet nucleus and coma studies. He studied sungrazing comets for his Ph.D. thesis and has spent 150+ nights observing comets in optical and near-IR wavelengths. Matthew's primary role on the CIOC is to monitor ISON and help predict its behavior near perihelion and beyond in order to help ground- and space-based observers optimize their observations.

[scalbers]

I gather Matthew Knight is continuing to do photometry with STEREO-A images? I could see some ISON brightening looking casually at them the past 12 hours. Encke is there too.

http://secchi.nrl.navy.mil/sccimages/index...4&nothumb=0

[Mongo]

Daylight photo of ISON, taken at 13:00 today by Astronomia Dominicana.

[Mongo]

Matthew Knight's Observation logs, taken from the STEREO A spacecraft's HI-1 instrument. I assume that the dates in the first two reports were switched at some point, unless he has a time machine.

Nov 21 : “Comet ISON had an apparent magnitude of 5.0 in an 11.7 arcmin diameter aperture on Nov 22.21 as viewed by STEREO-HI1A (Δ=1.0 AU; approximately V magnitude).”

Nov 22 : “Comet ISON had an apparent magnitude of 4.3 in an 11.7 arcmin diameter aperture on Nov 20.97 as viewed by STEREO-HI1A (Δ=1.0 AU; approximately V magnitude).”

Nov 25 : “As of Nov 25.63 ISON has an apparent V magnitude of 4.4 in an 11.7 arcmin diameter aperture in STEREO-HI1A images. It has trended smoothly brighter over the preceding ~0.5 day. I have not noticed any significant difference in the coma morphology since my previous report.”

Nov 26 : “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.”

[scalbers]

Just off the cuff it seems it would have to be brighter than 4th magnitude to show up in the Astronomia Dominicana image...

[Mongo]

Just off the cuff it seems it would have to be brighter than 4th magnitude to show up in the Astronomia Dominicana image...

There is serious doubt that they actually photographed comet ISON:

Daniel Fischer @cosmos4u 1h

Did they really image comet #ISON today in broad daylight in the Dominican Republic as http://www.astronomiadominicana.blogspot.d...o-logramos.html … sez? Why no higher mag. views?

Sungrazer Comets @SungrazerComets 56m

@cosmos4u As of 12UT today, Matthew thinks #ISON would have been around mag 3 as seen from Earth. So no, they did not see ISON.

Not to mention that upon examination, the short "tail" is pointing about 30 degrees away from the Sun. Is this possible, considering that it's heading almost directly toward the Sun? I now doubt that this object is actually ISON.

[JohnVV]

This is how it will look from Detroit in the morning
12:30 to 14:00 UT


But with a fainter tail - this one is way too bright

[Mongo]

Very informative NASA infographic about which NASA space assets observed -- or failed to observe -- comet ISON.

[scalbers]

There is serious doubt that they actually photographed comet ISON:

Daniel Fischer @cosmos4u 1h

Did they really image comet #ISON today in broad daylight in the Dominican Republic as http://www.astronomiadominicana.blogspot.d...o-logramos.html … sez? Why no higher mag. views?

Sungrazer Comets @SungrazerComets 56m

@cosmos4u As of 12UT today, Matthew thinks #ISON would have been around mag 3 as seen from Earth. So no, they did not see ISON.

Not to mention that upon examination, the short "tail" is pointing about 30 degrees away from the Sun. Is this possible, considering that it's heading almost directly toward the Sun? I now doubt that this object is actually ISON.

Yes, the "tail" is pointing in the wrong direction. It could be some lens aberration? Could they have spotted Mercury? I will say ISON was at about the right azimuth (to the right of the sun). It also seems the aureole around the sun is fairly bright, so this would make it pretty difficult to ferret out the comet.

Steve

[Mongo]

ISON is now entering the field of view of SOHO. The most recent SOHO LASCO C3 image can be found here, and at the current time shows ISON entering on the right.

[titanicrivers]

And check this out!! I thought that LASCO C3 showed an artifact but the LASCO C2 shows what appears to be a substantial CME directed towards ISON (superficially at least; might have a tail disconnect coming up!)



p.s. Click on the SOHO moview theater http://sohodata.nascom.nasa.gov/cgi-bin/soho_movie_theater
for the best experience with this site.

[dilo]

Collage of recent SOHO images (Lasco3+2+EIT314):

The new CME is clearly pointing toward the comet!

[remcook]

From spaceweather.com: "This CME, however, will probably miss. The source of the cloud is a farside active region, which is not directly facing the comet." A shame (maybe), but still makes for very pretty pictures

[Mongo]

posted by biver_nicolas this morning:

Re: No good news for ISON

Dear All,

The comet is apparently not dead yet (its coma starts saturating LASCO images as Antares?):

Today at IRAM I marginally detected emission for HCN around 10-12 UT

If I take into account the possibly high temperature in the coma it may be outgassing half as much as during the Nov 14 to 22 outburst.

But the line seems weaker at some other times. Otherwise it looked like peaking close to the latest ephemeris position (with strong A1/A2 non grav. parameters)... but this marginal, still.

Nicolas

So the gas emissions are still below the Nov 14-22 outburst, but their presence indicates that ISON still has a nucleus (although perhaps not the same size as before) and has not fully disrupted. My own guess would be that ISON had "switched off" for some reason several days ago, perhaps after all the easily vaporized surface deposits had finished evaporating (remember that ISON is probably a first-time visitor to the inner Solar System), and is now switching back on as it approaches perihelion and the solar heating reaches below the newly formed surface crust.

edit -- these Tweets just came in:

Sungrazer Comets @SungrazerComets 15m

Latest from Matthew Knight: Comet #ISON has increased in brightness by at least a factor of 4 since entering the LASCO data. Yay! #CIOC

Sungrazer Comets @SungrazerComets 3m

Sweet!! Looking at LASCO data/results and I can tell you that #ISON is now definitely behaving like a sungrazer!

edit -- another Tweet following explaining the above:

Sungrazer Comets @SungrazerComets 14m

@Nascarnoll Basically #ISON is starting to brighten at a ridiculous rate compared to how comets normally behave. That's what sungrazers do.