[meteorite-list] Leonids (was Holmes Swallows...)

From: mexicodoug <mexicodoug_at_meteoritecentral.com>
Date: Mon, 19 Nov 2007 19:07:38 -0600
Message-ID: <00ab01c82b11$bf47eee0$4001a8c0_at_MICASA>

Dear Listees,

Three weeks ago I posted our observational results for the viewing of Comet
Holmes (currently the largest member of the Solar System), and the Leonids
meteor shower peak November 17/18 gave motivation to hike back to the same
site and view the comet with the same binoculars: A 25X100mm astronomy pair
and a16X50mm pair typical of Walmart bought for US $60.

So, let me make a few comments of potential interest to meteorite people on
what we saw in the Leonids, and then give a few impressions of the comet and
how much longer this will be spectacular for most observers.

Leonids: The night began with a half-Moon, but one wouldn't have known, as
upon arrival the entire region was blanketed with various degrees from
disasterous to unthinkable swarths of angry clouds. Every minute, the
desert and sky would become brilliantly illuminated by multiple meteoric
flashes - however, they were "just" amazing lightening bolts that cast all
kinds of eerie shadows and blinded ones night vision in the pitch darkness.
Hurredly we went to sleep in the tent within the tent, a construction for
just such ocassions requiring waterproofing. Set the alarm for 4:00AM and
said our prayers amid lamentations.

At 4:00am, I couldn't see anything outside the windows, but luckily I
remembered their was a tent covering the windows. Morbidly I lifted the
outer flap covering the windows. *pinch* The sky was a 7th magnitude
limiting magnitude at this high altitude, clear and enough to make any
astronomer's heart sing. As if to re-enforce the shell-shock as I emerged
from our bunker, right through the Moonless sky, a slow, sporadic, fireball
painted it way across the sky, crossing of all places, Leo! It was about 0
magnitude and enough to leave a persisting smoke trail momentarily as it
went from what felt like brilliant star-lit horizon to perfectly transparent
horizon. Great!!! Venus was just rising, sitting on top of a distant
mountaintop.

The Leonid show is always a great show as frequently bright fireballs can be
seen, though typically the rate is not one of the absolute best. Under
optimal circumstances this year was to be 10-25 meteors per hour with an
overhead radiant. Well! the radiant over half way to the zenith and rising
inside Leo's mane placed not far from a golden and respectful Saturn. We
saw approximately 25 meteors during two hours, which actually slightly beat
the odds., but let me explain first the beauty of this meteor shower for
meteorite collectors, before I explain why.

Of the 25 meteors observed, about half were as bright as planets, which is
very exciting. These fireballs enter at extremely fast speeds (no more
smoke trails or long-lasted meteors, unfortunately, but...) four of the
meteors were fireballs that split much like fireworks, near their visual
endpoints. Not only did these split, but they were different colors. The
brightest of all was green (at least initially, as this can be hard to keep
track of when you are taking a photo and your observing partner screams to
look at the incredible green one). My head was down in a canister of film
[yes, I still use film] when that one passed overhead, but no scream was
necessary. This is because the fireball noticeably lit up the entire desert
in one of those spine-tingling flash events you think, BOLIDE! METEORITES!
SONIC BOOM???!! No, there was no sonic boom, but my head did snap up so
fast to the instant of the end of the lighted path and fragmentation - a
sight to behold. That is about as close as I've ever come to other lucky
observers see when a real meteorite-dropper across their their skies...and
hopefully into their back yard. This bolide was somewhat brighter than
Venus, conservatively, so I am thinking it was probably initially atound the
one gram range. One problem with hoping for meteorites from Leonids,
besides their need for speed, is that they are thought to be composed of
extremely friable material (the residue from Comet Swift-Tuttle).

The other extremely bright fragmentors during the luminescent path were
reddish and bluish-white colors, and the colors were so brilliant!
Virtually every Leonid that darted through the sky seemed like a big one. I
mentioned that our we saw 25 meteors in two hours, but that that was on the
hight side of optimal expectations. This is because, shortly after Venus
climbed in the Eastern sky, we found the interference the planet caused
unacceptable while our Western half-sky was wonderful. We positioned our
Vehicle between us and Venus, so this interference was minimized and looked
basically from Leo westwards. So we only had half of the 25 per hour rate,
having seen 25 amazing meteors in a magical two hour period while ignoring
the part of the sky Venus muddied out.

There came a time that the Sun overtook Venus a little after 6:00am, but we
couldn't resist in the now quite cold and somewhat windy desert the famous
"OK, we'll both see one more good one" starstruck syndrome...and there was
one rather good one right through the horns of Taurus when ub that
constellation, only the brightest star, a red giant, ALDEBARAN (15th
brightest in the entire sky over the year) was still visible. That must
have been quite a bright fireball!

Comet Holmes: Just a few comments for an apple to apple comparison three
weeks ago, through the eyes of my junior observing partner.

Three weeks ago: It looks like a perfectly formed circular scoop of almond
colored ice-cream with strong demarcation against the black background...
Leonid night out:: the bright star [Mirphak] is inside the comet on the
[trailing] side which finely fades like a torn cotton candy into the star
and then the darkness. The front end looks like like a cloud that is still
rounded, but everything is disappearing like vapors merging into the air
from a chimney. No color apparent other than a blurry-cloudy white
mixture...

Comet Forecast: On November 18, by naked eye in a dark sky, Mirphak looked a
little blurry, especially to one side. Sharper eyes easily could separate
the comet, but it has lost most of its visible impact. That's it for the
dramatic show. See it over the next couple of days a couple of hours before
sunrise at mid latitudes, if you can. In another week it won't be visible
except in nice dark sky locations, unless of course, there is a new
"erruption"...this in consideration that the Moon will be starting to
interfere by then, too...farewell, for now, Holmes, and thanks for your
spectacular performance...

Good Health and Best Wishes,
Doug









----- Original Message -----
From: "dmouat" <dmouat at dri.edu>
To: "Jerry" <grf2 at verizon.net>
Cc: <meteorite-list at meteoritecentral.com>
Sent: Monday, November 19, 2007 3:30 PM
Subject: Re: [meteorite-list] Fw: Comet Holmes Swallows a Star


> Dear Listees
>
> I checked out Comet "Bob" Holmes last night from the very clear skies of
> Truckee, California (1,800m; 6,000') with a decent pair of binocs. Mirfak
> was touching the east side of the comet. A very impressive
> (spectacular??) sight and you don't need a telescope.
>
> Dave
>
> Jerry wrote:
>
>> check this out. unfortunately for me it's clouded over tonight
>> Jerry Flaherty
>> ----- Original Message ----- From:
>> <Space.Weather.Alert.Service at spaceweatherphone.com>
>> To: <grf2 at verizon.net>
>> Sent: Monday, November 19, 2007 4:10 PM
>> Subject: Comet Holmes Swallows a Star
>>
>>
>>> Hi, This is Dr. Tony Phillips calling with an alert about Comet Holmes.
>>> It's Monday, Nov. 19th.
>>>
>>> This a message for people with backyard telescopes. Tonight, Comet
>>> 17P/Holmes will swallow a star! Not really, but the comet will pass
>>> directly in front of the star--named Mirfak, the brightest star of the
>>> constellation Perseus. The overall effect will be that of a giant cosmic
>>> jellyfish swallowing a phosphorescent treat. You can see it happen
>>> through even a small backyard telescope. The stellar "meal" will
>>> continue for the next few nights, so if you miss it tonight, try again
>>> tomorrow.
>>>
>>> SKY MAP:
>>> http://spaceweather.com/images2007/15nov07/skymap_north_holmes.gif
>>> PHOTO GALLERY: http://spaceweather.com/comets/gallery_holmes_page18.htm
>>
>>
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>
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Received on Mon 19 Nov 2007 08:07:38 PM PST