Comet ISON News and Links - 2013

Re: Comet ISON News and Links - 2013

Postby Guest » Fri Nov 29, 2013 12:36 am

I say we call it a tie. While the comet did break up, a bit of it did survive.

I wonder if any post analysis of the SDO data will reveal any sort of clues as to what happened. I mean we kind of know what happened, but I mean I wonder if any post processing will show the comet breaking up.

Below is the SOHO C2 image showing what's left of ISON.
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Re: Comet ISON News and Links - 2013

Postby william-kowalczyk » Fri Nov 29, 2013 10:21 am

Nice sequence of the latest C3 here:

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Re: Comet ISON News and Links - 2013

Postby william-kowalczyk » Fri Nov 29, 2013 11:16 am



Last edited by william-kowalczyk on Mon Dec 02, 2013 8:54 am, edited 1 time in total.
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Re: Comet ISON News and Links - 2013

Postby Guest » Sat Nov 30, 2013 7:45 pm

Bye bye ISON!!!

It appears ISON really didnt survive. It was evident late last night that whatever was left of ISON was not as bright in SOHO C3 anymore. By midday today it appeared that everyone was in agreement that the comet had fallen apart. It is currently barley visible as a faint fuzzy spot in the C3 images. Below is a raw image from the SOHO C3. Whats left of ISON is the very faint fussy area to the bottom left.


Re: Comet ISON News and Links - 2013

Postby Guest » Sat Nov 30, 2013 9:17 pm

ISON now visible in the STEREO-A HI-1


Re: Comet ISON News and Links - 2013

Postby william-kowalczyk » Mon Dec 02, 2013 8:43 am

One last video on ISON. I posted this on the netslyder as well...

Also here is a scientific synopsis from the various scietific opservations of the event:

Electronic Telegram No. 3731
Central Bureau for Astronomical Telegrams
CBAT Director: Daniel W. E. Green; Hoffman Lab 209; Harvard University;
20 Oxford St.; Cambridge, MA 02138; U.S.A.
e-mail:[email protected] ([email protected])
Prepared using the Tamkin Foundation Computer Network

The comet's nucleus apparently disrupted near perihelion, with the
comet's head fading from perhaps a peak brightness of visual mag -2 some
hours before perihelion to well below mag +1 before perihelion. M.
Knight, Lowell Observatory, finds that the comet peaked around visual
mag -2.0 around Nov. 28.1 UT, adding that the brightest feature in the
coma of the comet faded steadily after perihelion from about mag 3.1 in
a 95"-radius aperture when the comet first appeared from behind the SOHO
coronagraph occulting disk on Nov. 28.92 to about mag 6.5 on Nov.
29.98. K. Battams, Naval Research Laboratory, writes that, based on the
most recent LASCO C3 images (Nov. 30.912 UT), there is no visible
nucleus or central condensation; what remains is very diffuse, largely
transparent to background stars, and fading; it appears that basically a
cloud of dust remains from the nucleus. S. Nakano, Sumoto, Japan,
writes that he measured the comet's total magnitude in a 27' photometric
aperture from the SOHO C3 camera images to be as follows: Nov. 29.383,
0.5; 29.755, 1.4; 30.013, 2.0; 30.496, 3.0; 30.883, 5.4.

Z. Sekanina, Jet Propulsion Laboratory, reports that, from the
position of the northeastern boundary of the comet's fan-shaped tail in
three images taken with the C3 coronagraph onboard the SOHO spacecraft
between 0.7 and 1.9 days after perihelion (Nov. 29.46 to 30.66 UT), he
finds that the comet's production of dust terminated about 3 hours
before perihelion. Although this result is preliminary, it is unlikely
to be significantly in error, because the position angles of a
perihelion emission are off in the three images by 14-22 deg, and those
of post-perihelion emissions still more. The peak radiation-pressure
accelerations derived from the tail boundary's angular lengths
(estimated at 1.8-2.5 deg) are about 0.1-0.2 the solar gravitational
acceleration, implying the presence of micron-sized particles. The
estimated time of terminated activity is consistent with the absence of
any feature that could be interpreted as a condensation around an active
nucleus in the 20 or so images taken with the C2 coronagraph on Nov.
28.8-29.0 UT (0.8 to 5.4 hr after perihelion) and with the appearance of
a very sharp tip (replacing a rounded head) at the comet's sunward end
in the C2 images starting about 4 hr before perihelion and continuing
until its disappearance behind the occulting disc around Nov. 28.74 UT
(or some 50 minutes before perihelion). The time of terminated activity
is here interpreted as the end of nuclear fragmentation, a process that
is likely to have begun shortly before a sudden surge of brightness that
peaked nearly 12 hr prior to perihelion. Fine dust particles released
before perihelion moved in hyperbolic orbits with perihelion distances
greater than is the comet's, thus helping some of them survive. The
post-perihelion tail's southern, sunward-pointing boundary consists of
dust ejected during the pre-perihelion brightening. However, the
streamer of massive grains ejected at extremely large heliocentric
distances, so prominently seen trailing the nucleus along the orbit
before perihelion (cf.CBET 3722), completely disappeared. The dust
located inside the fan, between both boundaries, was released in
intervening times, mostly during the last two days before perihelion.
The strong forward-scattering effect (phase angles near 120-130 deg) has
tempered the rate of post-perihelion fading of the comet, but the
merciless inverse-square power law of increasing heliocentric distance
is necessarily the dominant factor in the comet's forthcoming gradual

H. Boehnhardt, J. B. Vincent, C. Chifu, B. Inhester, N. Oklay, B.
Podlipnik, C. Snodgrass, and C. Tubiana, Max Planck Institute for Solar
System Research, Katlenburg-Lindau, reports that two diffuse tail
structures were analyzed in post-perihelion images obtained by the
LASCO-C3 corongraph onboard the SOHO spacecraft between Nov. 29.60 and
29.81 UT. The southward tail extended toward p.a. about 167 deg to
about 0.4 deg distance from the central brightness peak. The eastward
tail had an approximate position angle of 68 deg and extended to at
least 1.2 deg distance. By Finson-Probstein simulations, the eastward
tail can best be interpretated as being caused by a dust release about 1
hr around perihelion. The maximum beta value in the eastward tail
reaches values up to 1.5, typical for graphite or metallic grains of
about 0.1 micron radius. No indications are found for a continuation of
the release of similar dust after 2 hr post-perihelion. The shorter
southward tail may be a relict of heavier grains released about 1-2 days
before perihelion passage. Diffuse cometary material is noticeable in
the p.a. range covered by the two dust tails. The match of the
synchrone pattern for the eastward tail is not optimal, which may
indicate secondary effects to the dust grains involved.

NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
superseded by text appearing later in the printed IAU Circulars.

(C) Copyright 2013 CBAT
2013 December 1 (CBET 3731) Daniel W. E. Green
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Re: Comet ISON News and Links - 2013

Postby william-kowalczyk » Mon Dec 02, 2013 8:55 am

CIOC's Memoriam

Comet C/2012 S1 (ISON)
Born 4.5 Billion BC, Fragmented Nov 28, 2013 (age 4.5-billion yrs old)

Born in a dusty and turbulent environment, comet ISON spent its early years being jostled and struck by siblings both large and small. Surviving a particularly violent first few million years, ISON retreated to the Oort Cloud, where it maintained a largely reclusive existence for nearly four billion years. But around 3-million B.C., a chance encounter with a passing star coerced ISON into undertaking a pioneering career as a Sungrazer. On September 21, 2012, ISON made itself known to us, and allowed us to catalog the most extraordinary part of its spectacular vocational calling.

Never one to follow convention, ISON lived a dynamic and unpredictable life, alternating between periods of quiet reflection and violent outburst. However, its toughened exterior belied a complex and delicate inner working that only now we are just beginning to understand. In late 2013, Comet ISON demonstrated not only its true beauty but a surprising turn of speed as it reached its career defining moment in the inner solar system. Tragically, on November 28, 2013, ISON's tenacious ambition outweighed its ability, and our shining green candle in the solar wind began to burn out.

Survived by approximately several trillion siblings, Comet ISON leaves behind an unprecedented legacy for astronomers, and the eternal gratitude of an enthralled global audience. In ISON's memory, donations are encouraged to your local astronomy club, observatory or charity that supports STEM and science outreach programs for children.

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Re: Comet ISON News and Links - 2013

Postby Guest » Mon Dec 02, 2013 10:03 pm

As Bill showed, comet ISON is pretty much gone. In the latest STEREO-A HI-1 images ISON is no longer visible. So with that I wanted to share some final images and a funny tweet from Perihelion Day.

First some of the latest images. About a day or two after Perihelion and a few hours before leaving the FOV of SOHO, ISON again showed up in HI-1 as it headed out of the solar system, or what was left of ISON. ISON remains in view until about 2118UT. In that image ISON is no longer visible. So this either means what was left of the comet moved out of view or finally dissipated. Word is that Hubble will attempt to image the remnants this month. The week after next i believe.

Also the first high resolution images of this event are finally visible. ... &nothumb=0

I had a great time tracking ISON. I became part of the CIOC group on facebook. Sadly the weather and my schedule conspired against me, so I was unable to make any observations before Perihelion. But I was able to provide image updates from SOHO and STEREO.


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