Re: Any good memorable comets coming soon? Like Ikeya-Zhang Hale-Bopp

In article <1161613453.078069.109830@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
CNJ999 <jbortle@xxxxxxx> wrote:

In point of fact,

Rephrase that to "In point of my opinion" .... see below:

there hasn't been a "classic" Great Comet is 30
years. While H-B and Hyakutake were in a sense rather spectacular, the
brightness of either's tail (usually the most outstanding feature of a
Great Comet) were but pale representations of what nearly all of the
Great Comets of the past have displayed. If we ever do get another
truly Great Comet, I expect today's observers will be utterly shocked
by its overall brilliance.

I don't know how easily shocked you are, but I actually saw two of
those comets you refer to below. It was fun, and I enjoyed them --
but I wasn't at all "utterly shocked" - instead I felt quite happy!
But I was more impressed by Hyakutake and though Hale-Bopp was quite
similar in "greatness". Read on....

The best time to have been an amateur astronomer interested in comets
was between 1957 and 1976, when Great Comets were literally
commonplace, with at least half a dozen appearing in the short span of
just 20 years!

"at least half a dozen" = at least 6, probably more ..... but below you
list only five comets...... :-)

In fact, it was the most prolific period for such
objects in recorded history. The only similar grouping of truly
briilliant comets took place about a century earlier than that and
there are no other contenders for the title. So...as pointed out up
stream...the typical historical odds for seeing a classical Great Comet
are no better than perhaps 2 or 3 over the course of a lifetime. Thus,
if you're wating for one...don't hold your breath!

JBortle








Paul - Regarding you comments, there is nothing subjective about my
statement.

:-)

To the average amateur astronomer who saw H-B or Hyakutake,
from a typical observing site, many comets of the past were far more
spectacular in overall impressiveness.

Ah, there's the catch: a "typical observing site" is today much more
light polluted than it was 100 or even 50 years ago.

Indeed, I saw Hyakutake on a number of nights from a site with
excellent sky conditions and could trace the tail 70 degrees
(incidentally, the reported 100+ degree tails were nonsense and
physically quite impossible under the circumstances). However, that
comet's tail was of quite low surface brightnes and the typical amateur
report credited it with a length of more like 10-15 degrees and very
faint at that. Likewise, while H-B did have a nice bright coma, except
for the first few dgrees, its tail was generally of low surface
brightness as well and relatively few amateurs saw more than ten
degrees or so in its span.

There is no selective memory involved when I say that the perhaps half
a dozen Great Comets visible between 1957 and 1976 out-shown both H-B
or Hyakutake.

True, however you do make things a bot over-simple when you consider
the "greatness" of comet to merely be its peak magnitude. Other things
matter too -- such as whether the comet at peak brightness can be seen
only in twilight skies, or if they also can be seen in fully dark skies
and if so, how high up in the sky the comet appears.

To me, it takes more to be impressed by a comet than to read a table
of peak magnitudes and there read "-3" .....

In fact, I saw each and, since comets have always been my
specialty, I can objectively compare one with another,

Now you're starting to sound like Percival Lowell: he was an expert on
MArs, and probably considered himself to be able to objectively observe
the surface features of that planet.....

having viewed them all under equally good skies and with considerable
observing experience.

Sorry, but a bright twilight sky isn't an "equally good sky" as a fully
dark sky!

1957 Arend-Roland. Peaked at -1, displayed very bright anti-solar AND
sunward-pointing tails, spanning a total of 45 degrees.

1962 Seki-Lines. Reached -3 and had an intensely bright, dramatically
curved, 20 degree tail.

1965 Ikeya-Seki. Visible briefly in the daytime with the unaided eye
with a magnitude of -8 to -14. After perihelion passage it unfurled a
25 degree tail with the highest surface brightness of any comet in the
20th century, looking over its entire length like a brilliant auroral
ray. Fully 15-20 degrees of nakedeye tail wase even reported visible
from within NYC!

1970 Bennett. Zero magnitude with a 20-25 degree, brilliant, tail. I
recall one morning watching this comet rise, complete with 5 degrees of
tail, from indoors while seated in the room watching TV with the room
lights on and simply glancing out through a closed window, waiting for
it to get up enough to properly observe!

1976 West. Attained -3; visible during the daytime with binoculars
looking like a fuzzy version of Venus and seen before sunset with just
the unaided eye. It displayed 5 tails (the result of its nucleus
breaking up into independant comets), the longest attaining fully 35
degree and showing a distinct deep reddish color!

In addition, during this same period, there were somewhat lesser but
still very bright comets like Comet Mrkos, of zero to first magnitude
with a 15 degree tail in 1957, Comet Wilson-Hubbard in 1961 at 2nd to
3rd magnitude with a 25 degree tail. Plus, Comet Pereyra, 3rd magnitude
with a 15 degree tail in 1963 and White-Ortiz-Bolelli in 1970 at 1st to
2nd magitude and displaying a dozen degrees of tail.

Any of these first 5 or 6

Let's count them - above you listed:

1. 1957 Arend-Roland.
2. 1962 Seki-Lines.
3. 1965 Ikeya-Seki.
4. 1970 Bennett.
5. 1976 West.

Yep, that's 5, not 6. And 5 isn't "at least half a dozen" ..... but I
suppose there's nothing subjective about your phrase here either.... :-)

In your list above you forgot Comet Kohoutek, which in Febr 1974
peaked at magnitude -3, but then it was so close to the Sun in the
sky that only astronauts onboard Skylab could observe it.
Nevertheless, by your simpleminded criterion "the greatness of a
comet depends only on its peak magnitude", Kohoutek should definitely
be included too - after all, it became about as bright as Comet West,
although people on Earth never had the chance to admire its full
splendor. Adding Kohoutek to your list will also perhaps save your
face, since 6 is indeed "at least half a dozen" by a minimum margin....

most any observer today would

....perhaps you should let "most any observer" speak for themselves
instead of putting your words into their mouths?

placed well above H-B or Hyakutake if they had a chance to compare
them side by side.

....which you know cannot be done. Put e.g. Ikeya-Seki of 1965 "side
by side" with Hyakutake right overhead in a fully dark sky - you know
what? If you did so, Ikeya-Seki would lose almost all of its grandeur,
because it would (for geometrical reasons) then have to be put much
farther from the Sun (around 1 AU) than it actually was.

Just because you or those today have never seen objects of such grandeur,

You're so full of prejudice !!! FYI: I saw both Bennett and West -- don't
tell me I didn't see them! And I don't think I'm the only one here who
saw them....

don't think they are products of a hazy memory. You'll be convinced
when a really good one comes along again.

JBortle

There's really only one reasonable way a comet could be intrinsically
brighter - by passing closer to the Sun at perihelion.: the closer to
the Sun, the brighter the comet will become. The most outstanding
examples here are of course the Kreutz family of comets, the last
really bright example of which was Ikeya-Seki in 1965. However, all
such comets will by necessity always appear in twilight skies, quite
close to the Sun in the sky. Bennet and West, both of which I was
back in 1970 and 1976, were both in twilight skies when brightest.
Hyakutake and Hale-Bopp could be seen in dark skies when brightest.
That made them more impressive, even though they were a bit fainter.

I'm not quite sure whan I would consider most impressive: a mag -5
comet in a bright twilight sky, or a mag 0 comet right overhead in a
completely dark night sky. In our times, the former is of course more
appealing on one way: it is less sensitive to light pollution.

But I don't expect to ever again see a comet of magnitude zero or
brighter, with a long tail, near to my local zenith in a fully
dark sky.... (for that to happen, the comet must be at least some
120 degrees away from the Sun in our sky -- Ikeya-Seki, Bennet or
West never managed to do that while still bright).


As you can see, the "greatness" of a comet is quite subjective: you
consider almost only the peak brightness of the comet, while I think
other circumstances is important too.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
.

Relevant Pages

  • Comet C/2007 W1 (Boattini) 7-17-2008
    ... 12', DC=0 to 3, no tail or coma detail seen under poor Moon washed sky ... of Comet C/2007 W1. ... It was near full Moon, so I tried for a brief observing window between ...
    (sci.astro.amateur)
  • Re: Comet Machholz from Nebraska
    ... > comet was easy to see not far southwest of the Pleiades. ... > its brightness is about magnitude 3.8 or so despite the sky brightness ... > clear signs of a tail with the unaided eye. ... > degree in length at most from the center of the coma. ...
    (sci.astro.amateur)
  • Ulysses Catches Record for Catching Comets by Their Tails
    ... Ulysses Catches Record for Catching Comets by Their Tails ... Ulysses' first cometary tail encounter occurred in 1996. ... comet Hyakutake was dazzling scientists and the public alike with its ... "The solar wind seemed to almost ...
    (sci.space.news)
  • Re: A 3D construction of Comet 17P
    ... People have been saying for days the tail does-not ... go back as most comet tails do, on the sun-comet line behind the ... comet, ... 3D construction of the comet and its tail was attempted to better ...
    (sci.astro.amateur)
  • Re: Comet Machholz from Nebraska
    ... > comet was easy to see not far southwest of the Pleiades. ... > of light brighter towards the middle with a little asymmetry in the brightness ... > degree in length at most from the center of the coma. ... > the dust tail was a bit brighter in its central portion than was the ion tail. ...
    (sci.astro.amateur)
Quantcast