[meteorite-list] MORE HOLMES NEWS'N'VIEWS

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Fri, 26 Oct 2007 15:37:21 -0500
Message-ID: <03b201c81810$02e2f1f0$b92ee146_at_ATARIENGINE>

Hi, Holmes Watchers and Watcher Wannabees,

    One thing we can say is that this comet has proven
that the usual comet rules do not seem to apply to it!
"Something" is going on that is outside the comet norm.
The usual solar heating of volatiles explanation seems
inadequate, particularly since it makes a perihelion passage
like last May's every seven-odd years without these displays.

    It may have suffered a massive impact. It may be in the
process of "splitting" like Biela. It may be doing something
we've never observed before (and hence know nothing
about).

    I hope that somebody besides fascinated amateurs are
prepared for observations beyond visual impressions. For
example, the usual course of an "outburst" is the development
of a variety of jets and fountains which produce distinctive
features in the coma (spikes, fans, pinwheels, etc.), but Holmes
seems to be producing material in almost perfect spherical
symmetry.

    This implies an uniform rate and speed of ejected material
which is difficult to explain. Perhaps so much material at such
high densities is being ejected that they are undergoing a
"scattering" process that would uniformatize particle speed.
But that would mean a huge volume of material ejected.

    What I like best about the universe is its surprises.


Biggest and Brightest?

Melbourne's Herald-Sun, under the headline
"Comet Homes On Its Way To Brightest in History"
http://www.news.com.au/heraldsun/story/0,21985,22655772-662,00.html
    "If the brightness continues at this rate, Comet Holmes
will soon become the brightest comet in history."


Long Lasting?

Observer report from Sky & Telescope's frequently updated site:
http://www.skyandtelescope.com/observing/home/10775326.html
    "Used the 12.5-inch reflector at 75x, 110x, and 180x.
A brilliant, starlike, white nucleus is dead center in the
perfectly round coma. What looked like the nucleus in
the binoculars is an inner coma or broad fan offset from
the nucleus toward the southwest. At these magnifications
the bright round disk is no longer perfectly sharp-edged,
but still nearly so. It also has a slight but definite ring
appearance, as if some of the light is coming from a
hollow, spherical, glowing shell. Farther out beyond
this is a much dimmer round glow with about twice
the diameter of the bright disk. Only out this far does
the brilliant skylight of the perigean full Moon not far
away begin to matter. This was at 1 a.m. EDT (5:00 UT)
October 26th with the comet (and Moon) near the zenith.
Still mag. 2.7 naked-eye. My bet is this comet will stay
bright for a long while. The yellow-white color is dust
reflecting sunlight, and dust is what keeps a comet bright.
As opposed to gas (comet gas is green and blue), which
blows away quickly in the solar wind. Also, the brilliant
stellar nucleus and the inner-coma fan suggest that the
nucleus is still producing a lot of dust. This comet won't
fade out soon. As for a tail: I expect it'll be short and
stubby when or if it forms. The tail should be pointing
more or less away from Earth in space; we're looking
down its length since the comet is only about 45 [degrees]
away from the point in the sky opposite the Sun. The
size of this angle won't change a lot in the next couple
months."


    Brightest Comet in History? It will have to reach
magnitude -4 to be visible in daylight, and it has stiff
competition for that title! Please note that most of these
made a very close perihelion passage; Holmes did not.
Most are super-bright because they are observed very
close to the Sun; Holmes is not. Whatever it's doing,
it's not the same as the superheating episodes that
created these bright comets.

GREAT COMET OF 1744: First sighted on Nov. 29,
1743 as a dim fourth magnitude object, this comet
brightened rapidly as it approached the Sun. Many
textbooks often cite Philippe Loys de Cheseaux, of
Lausanne, Switzerland as the discoverer, although his
first sighting did not come until two weeks later.
By mid-January 1744, the comet was described as
1st-magnitude with a 7-degree tail. By Feb. 1 it rivaled
Sirius and displayed a curved tail, 15-degrees in length.
By Feb. 18 the comet was equal to Venus and now
displayed two tails. On Feb. 27, it peaked at magnitude -7
and was reported visible in the daytime, 12-degrees
from the Sun. Perihelion came on March 1st, at a
distance of 20.5 million miles from the Sun. On March 6,
the comet appeared in the morning sky, accompanied
by six brilliant tails which resembled a Japanese hand fan.

GREAT COMET OF 1843: This comet was a member
of the Kruetz Sungrazing Comet Group, which has
produced some of the most brilliant comets in recorded
history. It passed only 126,000 miles from the Sun's
photosphere on Feb. 27, 1843. Although a few observations
suggest that it was seen for a few weeks prior to this date,
on the day when it made it closest approach to the Sun it
was widely observed in full daylight. Positioned only 1-degree
from the Sun, this comet appeared as "an elongated white
cloud" possessing a brilliant nucleus and a tail about 1-degree
in length.

GREAT SEPTEMBER COMET OF 1882: This comet is
perhaps the brightest comet that has ever been seen; a
gigantic member of the Kreutz Sungrazing Group. First
spotted as a bright zero-magnitude object by a group of
Italian sailors in the Southern Hemisphere on Sept. 1, this
comet brightened dramatically as it approached its rendezvous
with the Sun. By the 14th, it became visible in broad daylight
and when it arrived at perihelion on the 17th it passed at a
distance of only 264,000-miles from the Sun's surface.
On that day, some observers described the comet's silvery
radiance as scarcely fainter than the limb of the Sun,
suggesting a magnitude somewhere between -15 and -20!
The following day, observers in Cordoba described the
comet as a "blazing star" near the Sun. The nucleus also
broke into at least four separate parts. In the days and
weeks that followed, the comet became visible in the
morning sky as an immense object sporting a brilliant tail.
Today, some comet historians consider it as a "Super
Comet," far above the run of even Great Comets.

GREAT JANUARY COMET OF 1910: The first people
to see this comet-then already of first magnitude-were
workmen at the Transvaal Premier Diamond Mine in South
Africa on Jan. 13. Two days later, three men at a railway
station in nearby Kopjes casually watched the object for
20-minutes before sunrise, assuming that it was Halley's
Comet. Later that morning, the editor of the local
(Johannesburg) newspaper telephoned the Transvaal
Observatory for a comment. The observatory's Director,
Robert Innes, must have initially thought this sighting was
a mistake, since Halley's Comet was not in that part
of the sky and nowhere near as conspicuous. Innes
looked for the comet the following morning, but clouds
thwarted his view. But on the morning of the 17th, he
and an assistant saw the comet, shining sedately on the
horizon just above where the Sun was about to rise.
Later, at midday, Innes viewed it as a snowy-white
object, brighter than Venus, several degrees from the Sun.
He sent out a telegram alerting the world to expect "Drake's
Comet"-for so "Great Comet" sounded to the telegraph
operator. It was visible during the daytime for a couple
of more days, then moved northward and away from the
Sun, becoming a stupendous object in the evening sky
for the rest of January for the Northern Hemisphere.
Ironically, many people in 1910 who thought they had
seen Halley's Comet, instead likely saw the Great January
that appeared about three months before Halley.

COMET SKJELLERUP-MARISTANY, 1927: Another
brilliant comet, first seen as a third magnitude object in
early December, had the unfortunate distinction of being
situated under the poorest observing circumstances possible.
Located at a distance of 16.7 million miles from the Sun,
it was visible in daylight about 5-degrees from the Sun
at a magnitude of -6.

COMET IKEYA-SEKI, 1965: This was the brightest comet
of the 20th century, and was found just over a month before
perihelion passage in the morning sky moving rapidly toward
the Sun. Like the Great Comets of 1843 and 1882, Ikeya-Seki
was a Kreutz Sungrazer and on Oct. 21 swept to within
744,000 miles of the center of the Sun. The comet was
then visible as a brilliant object within a degree or two of
the Sun, and wherever the sky was clear, the comet could
be seen by observers merely by blocking out the Sun with
their hands, corresponding to a magnitude of -15.

COMET WEST, 1976: The last daylight comet sighting
until McNaught in 2007, but only visible for short times.




Sterling K. Webb
(Watcher Wannabee)
Received on Fri 26 Oct 2007 04:37:21 PM PDT