Comet C/2012 S1 (ISON)

[Rick]

Comet ISON Not Related to Comet Kirch of 1680, but...

Discovered in 1680 (hence the C/1680 designation), comet C/1680 V1 (Kirch), was first spotted by German astronomer Gottfried Kirch in early November, 1680, and holds the accolade of being the first comet to be discovered via a telescope! It also seems to hold the accolade as one of the most aliased comets in history, going also by the names of "The Great Comet of 1680", "Kirch's Comet", and "Newton's Comet"! (The latter is rather misrepresentative, as Newton himself played no part in the discovery, but he did use its orbit to demonstrate his new laws of orbital mechanics when they were published in the famous Principia several years later.) Just a couple of weeks following discovery, C/1680 V1 passed just 0.42AU (~62-million kilometers, or ~39-million miles) from Earth, and just a couple of weeks after that, on Dec 18, 1680, grazed a mere 0.006AU (~900,000km, 550,000miles) from the Sun -- not that far above the solar surface, and reputedly visible during broad daylight! As it raced away from the Sun, it peaked in brightness by the end of the year with a spectacularly long and thin arcing tail that spanned much of the nighttime skies before finally receding from view in early 1681. Sounds great, but what's the link to Comet ISON? Technically there isn't one... but for a while we really thought there was, and despite there not being a link, Kirch's Comet may still hold valuable clues to Comet ISON's fate...

More: http://www.isoncampaign.org/potw-jul22

[Rick]

NASA'S Spitzer Observes Gas Emission From Comet ISON

Astronomers using NASA's Spitzer Space Telescope have observed what most likely are strong carbon dioxide emissions from Comet ISON ahead of its anticipated pass through the inner solar system later this year.

Images captured June 13 with Spitzer's Infrared Array Camera indicate carbon dioxide is slowly and steadily "fizzing" away from the so-called "soda-pop comet," along with dust, in a tail about 186,400 miles (300,000 kilometers) long.

More: http://www.nasa.gov/mission_pages/spitzer/news/spitzer20130723.html and http://www.isoncampaign.org/

[Rick]

MRO Will Attempt to Image Comet C/2012 S1 (ISON)

There is a comet currently approaching the inner solar system that has been generating a lot of interest since its discovery last year: comet C/2012 S1 (ISON).

In August, ISON ought to be getting more active and developing its tail as it warms up, and astronomers want to get more information on this stage of the comet's development. Due to solar system geometry, ISON cannot be observed easily from Earth at this time - but it can be from Mars!

More

[Mike]

However, it's not looking good:

SKY AND TELESCOPE

[MarkS]

However, it's not looking good:

Do you mean to say the "comet of a lifetime" was over-hyped?

[Mike]

As usual.

[Rick]

The best comets often come as a surprise. All the hype just shows how little we actually know about comets.

[Rick]

Comet ISON to fly by Mars

Around the world, astronomers are buzzing with anticipation over the approach of Comet ISON.  On Thanksgiving Day 2013, the icy visitor from the outer solar system will skim the sun's outer atmosphere and, if it survives, could emerge as one of the brightest comets in years.

First, though, it has to fly by Mars.

"Comet ISON is paying a visit to the Red Planet," says astronomer Carey Lisse of the Johns Hopkins University Applied Physics Lab. "On Oct 1st, the comet will pass within 0.07 AU from Mars, about six times closer than it will ever come to Earth."

More here

[Rick]

Amateur Astronomers See Comet ISON

Anticipation is building as Comet ISON approaches the sun for a close encounter on Thanksgiving Day (Nov. 28). No one knows if the blast of solar heating ISON receives will turn it into one of the finest comets in years--or destroy the icy visitor from the outer solar system.

Astronomer Carey Lisse, the head of NASA's Comet ISON Observing Campaign, hopes that "every telescope on Earth will be trained on the comet in October and November."  He may get his wish. As September comes to an end, amateur astronomers around the world are already monitoring the comet.

...

Based on the latest images, internationally known comet expert John Bortle says "ISON appears likely to survive the in-bound leg of its journey all the way to the Sun. It will probably brighten more slowly than all the early hype led the public to believe. Nevertheless, Comet ISON should very briefly become exceptionally bright, at least rivaling the planet Venus in the hours preceding its closest approach to the sun."

More: http://science.nasa.gov/science-news/science-at-nasa/2013/24sep_ison2/

[Rick]

The actual observed magnitudes, particularly the recent ones, are clearly falling below the optimistic predicted curve. Anyone from the OAS imaged it yet?

[MarkS]

Anyone from the OAS imaged it yet?

It's on my list.  Need to wait until the moon is safely out of the way - maybe next week, weather permitting.

[Rick]

First HiRISE Images of Comet ISON

On 29 September 2013, the Mars Reconnaissance Orbiter (MRO) maneuvered to point its High Resolution Imaging Science Experiment (HiRISE) camera at ISON, a new comet passing by Mars on its way into the inner Solar System.

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.

More: http://www.uahirise.org/releases/ison.php

[MarkS]

Comet ISON's brightness curve is very similar to other comets that have faded and died:
http://arxiv.org/pdf/1310.0552v2.pdf

I hpoe they're wrong

[Rick]

Comet C/ISON Details Emerge as it Races Toward the Sun

Scientists are unraveling more information on Comet C/2012 S1 (ISON) as it continues on its journey toward the Sun. Comet C/ISON will skim 730,000 miles above the Sun's surface on Nov. 28 and has the potential to be readily visible from Earth starting in early December.

"We measured the rotational pole of the nucleus.  The pole indicates that only one side of the comet is being heated by the Sun on its way in until approximately one week before it reaches it closest point to the Sun," said Planetary Science Institute Research Scientist Jian-Yang Li, who led a team that imaged the comet.

"Since the surface on the dark side of the comet should still retain a large fraction of very volatile materials, the sudden exposure to the strong sunlight when it gets closer to the Sun than Mercury could trigger huge outbursts of material," Li said.

Li presented the findings today at the American Astronomical Society's Division for Planetary Sciences 45th Annual Meeting in Denver.

More: http://www.psi.edu/news/ISON3.html

[Rick]

Comet ISON Appears Intact

A new image of the sunward plunging Comet ISON suggests that the comet is intact despite some predictions that the fragile icy nucleus might disintegrate as the Sun warms it. The comet will pass closest to the Sun on November 28.

In this NASA Hubble Space Telescope image taken on October 9, 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.

Moreover, the coma or head surrounding the comet's nucleus is symmetric and smooth. This 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.

More: http://hubblesite.org/newscenter/archive/releases/2013/42/image/a/