[meteorite-list] Potentially Dazzling Comet ISON Now Visible to Naked Eye After Outburst

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 14 Nov 2013 13:03:25 -0800 (PST)
Message-ID: <201311142103.rAEL3PKQ021477_at_zagami.jpl.nasa.gov>

http://www.space.com/23591-comet-ison-visibility-naked-eye.html

Potentially Dazzling Comet ISON Now Visible to Naked Eye After Outburst
by Joe Rao
space.com
November 14, 2013

Get ready for a stellar show. The much-anticipated Comet ISON is now visible
to the naked eye according to reports from many observers.

Comet ISON - the potential "comet of the century" - has suddenly brightened
in an outburst of activity with just two weeks to go before it literally
grazes the surface of the sun,

In recent months, Comet ISON has repeatedly befuddled forecasters trying
to anticipate just how bright it will ultimately become. But earlier this
week, the comet's brightening trend again seemed to sputtering and stalling,
but more recent observations suggest a sudden and radical upsurge in brightness.

Comet ISON lightens up, literally

Comet ISON is now in full outburst mode, becoming many times brighter
over just the past few days. Astronomers measure the brightness of objects
in the night sky as magnitude, in which the brighter an object is, the
lower its magnitude number. The human eye can perceive objects as faint
as magnitude +6.5.

According to veteran comet observer, John Bortle, Comet ISON was shining
only at magnitude +8.5 on Monday (Nov. 11) morning - more than six times
too dim to be visible to the unaided eye. But by Wednesday morning, the
comet's brightness had increased three-fold brightening to +7.3.

If that was a surprise, an even bigger one was waiting for Bortle on Thursday
morning (Nov. 14).

"Ready to go at 4:45 a.m. but I couldn't figure out what the funny-looking,
blotted, star that came into view was," Bortle said. "[Was my] seeing
that bad? But, no, the 'blotted star' was, in fact, at the comet's position!
Getting to the point, the little but intensely condensed, globular cluster-looking
comet was a whopping magnitude 5.4 - two full magnitudes brighter than
just 24 hours ago! This makes for a three magnitude total rise since my
observation on Monday."

In just 72 hours, Comet ISON increased nearly 16 times in brightness.

Carl Hergenrother, acting co-coordinator of the comet section of the Association
of Lunar and Planetary Observers, has confirmed Bortle's observations.

"ISON has dramatically brightened over the past few days," Hergenrother
told SPACE.com via email. "The latest observations put the comet around
magnitude 5.7 to 6.1 which is a 2+ magnitude increase from this weekend.
My own observations from this morning in 10x50 and 30x125 binoculars show
a nice 'lollipop' comet with a very condensed blue-green head and a long
narrow tail. The tail was over 1 degree in length even in the 10x50s.
The comet may continue to brighten as the outburst is still in its early
stages."

Long Island amateur Dennis Wilde was also impressed by ISON's appearance
in the predawn sky Thursday morning.

"ISON, while not as large as the full moon, was an impressive sight in
the eyepiece," Wilde said. "The coma was compact with a very bright apparent
nucleus, very bright green in color. The tail was very thin and bright
near the coma and widened slightly as it extended out to almost 3.5 degrees
as seen in the 15". It wasn't huge or extraordinarily bright but it was
a great view nonetheless. I viewed the coma at up to 490x and it was uniformly
dense and bright. There was no indication of the start of any breakup.
After finding it with the telescope it was quite easy to pick out the
coma with the [binoculars]."

This outburst is not completely unusual since ISON has demonstrated short
"spurts" of brightening over the past few weeks, but they were quickly
followed by abrupt slow-down in its brightening trend.

So will the current outburst persist until the comet arrives at the sun
on Thanksgiving Day (Nov. 28)?

"Whether by chance we have caught the comet at the peak of the outburst
is certainly debatable (to me rather improbable) and it may well still
brighten further," Bortle said.

"The comet may continue to brighten as the outburst is still in its early
stages," Hergenrother said. "Whether this outburst will be a short-lived
event or the beginning of a more active phase is still to be seen."

This sudden upsurge in brightness is certainly very good for a comet that
until now seemed to be running well behind in brightness predictions.
It seems now that we can feel a little more optimistic about this enigmatic
object putting on show for us later this month on into early December.


Comet ISON was first discovered by Russian amateur astronomers Vitali
Nevski and Artyom Novichonok in September 2012. The comet is officially
designated C/2012 S1 (ISON), with ISON standing for International Scientific
Optical Network.

The comet is rapidly approaching its Nov. 28 perihelion and as a result
it is becoming more and more difficult to observe low near the east-southeast
horizon in the dawn sky. Still, observers with access to a clear horizon
may be able to follow ISON for about another week.

Next Monday morning (Nov. 18), ISON will be passing close to the bright
1st magnitude star Spica in Virgo. Using the handle of the Big Dipper,
sweep an arc to the brilliant orange star Arcturus. Then continue that
arc on to Spica. Using binoculars, ISON should still be readily be visible
as a fuzzy star with a short tail.

Will it still be visible to the unaided eye? Check it out for yourself!
Received on Thu 14 Nov 2013 04:03:25 PM PST