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(meteorobs) Excerpts from "CCNet, 019/2000 - 11 February 2000"
------- Forwarded Message
From: Benny J Peiser <b.j.peiser@livjm.acdot uk>
To: cambridge-conference@livjm.acdot uk
Subject: CCNet, 11 February 2000
Date: Fri, 11 Feb 2000 10:46:04 -0500 (EST)
CCNet, 019/2000 - 11 February 2000
----------------------------------
QUOTES OF THE DAY
"SOHO is seeing fragments from the gradual breakup of a great=20
comet, perhaps the one that the Greek astronomer Ephorus saw in=20
372 BC," said Dr. Brian Marsden of the Center for Astrophysics in=20
Cambridge, MA. "Ephorus reported that the comet split in two. This =
fits with my calculation that two comets on similar orbits=20
revisited the Sun around AD 1100. They split again and again,=20
producing the sungrazer family, all still coming from the same=20
direction." Their ancestor must have been enormous by cometary=20
standards. "The rate at which we've discovered comets with LASCO=20
is beyond anything we ever expected," said Biesecker.=20
--- Space Science News, 10 February 2000
"We need detectors in Space, whether they have military bearings or =
not. Comet debris trails might just be the most difficult encounter =
situation to mitigate and we don't know much about them except that =
they are hard to detect from the ground."
-- Bob Kobres, 11 February 2000 =20
(1) WHEN BIG COMETS COME UNGLUED
Bob Kobres <bkobres@ugadot edu>
(2) KAMIKAZE COMETS
Space Science News, 10 February 2000
(3) KAMIKAZE COMETS DON'T STAND A SNOWBALL'S CHANCE IN HELL
Space.com, 9 February 2000
[...]
(6) NEAR TO ASTEROIDS
SPACEDAILY, 11 February 2000
(7) THE TOP FACTOIDS ABOUT ASTEROIDS
MSNBC, Space News, 10 February 2000
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
(1) WHEN BIG COMETS COME UNGLUED
>From Bob Kobres <bkobres@ugadot edu>
=20
From:
http://spacescience.com/headlines/y2000/ast10feb_1.htm=20
"SOHO is seeing fragments from the gradual breakup of a great comet,=20
perhaps the one that the Greek astronomer Ephorus saw in 372 BC," said=20
Dr. Brian Marsden of the Center for Astrophysics in Cambridge, MA.=20
"Ephorus reported that the comet split in two. This fits with my=20
calculation that two comets on similar orbits revisited the Sun around=20
AD 1100. They split again and again, producing the sungrazer family,=20
all still coming from the same direction." =20
Their ancestor must have been enormous by cometary standards. "The rate =
at which we've discovered comets with LASCO is beyond anything we ever=20
expected," said Biesecker. "We've increased the number of known=20
sungrazing comets by a factor of four. This implies that there could be =
as many as 20,000 fragments."=20
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I wonder what the actual large fragment count of the Taurid Complex=20
progenitor might be? =20
http://abob.libs.ugadot edu/bobk/taurid.html =20
We need detectors in Space whether they have military bearings or not. =
Comet debris trails might just be the most difficult encounter=20
situation to mitigate and we don't know much about them except that=20
they are hard to detect from the ground. =20
http://adsbit.harvarddot edu/cgi-bin/nph-iarticle_query?1988ApJ...334L..55S=
=20
Later
Bob Kobres
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
(2) KAMIKAZE COMETS
>From Space Science News, 10 February 2000
http://spacescience.com/headlines/y2000/ast10feb_1.htm
Ninety-two sungrazing comets discovered by SOHO appear to have=20
come from the breakup of a single gigantic comet more than 2000=20
years ago.
February 10, 2000 -- In just four years of operation, the Solar and=20
Heliospheric Observatory (SOHO) spacecraft has found 102 comets, making =
it by far the most successful comet-hunter in history. Most of this=20
amazing number are suicidal comets that vaporize as they plunge into=20
the solar atmosphere.=20
One hundred years ago Heinrich Kreutz in Kiel, Germany, realized that
several comets seen buzzing the Sun seemed to have a common origin,=20
because they came from the same direction among the stars. These comets =
are now called the Kreutz sungrazers. A whopping 92 of SOHO's 102 comet =
discoveries belong to that class.=20
Nearly all of SOHO's comet discoveries have showed up in images from=20
the Large Angle and Spectrometric Coronagraph (LASCO) instrument. This=20
is a set of coronagraphs that view the space around the Sun out to 12.5 =
million miles, while blotting out the bright solar disk with masks.=20
LASCO watches for ejections of electrically charged gas from the Sun=20
that threaten to disturb the Earth's space environment. As a bonus of=20
unanticipated size, it also proved ideal for capturing objects falling=20
to the Sun.=20
"SOHO is seeing fragments from the gradual breakup of a great comet,=20
perhaps the one that the Greek astronomer Ephorus saw in 372 BC," said=20
Dr. Brian Marsden of the Center for Astrophysics in Cambridge, MA. =20
"Ephorus reported that the comet split in two. This fits with my=20
calculation that two comets on similar orbits revisited the Sun around=20
AD 1100. They split again and again, producing the sungrazer family,=20
all still coming from the same direction."=20
Their ancestor must have been enormous by cometary standards. "The rate =
at which we've discovered comets with LASCO is beyond anything we ever=20
expected," said Biesecker. "We've increased the number of known=20
sungrazing comets by a factor of four. This implies that there could be =
as many as 20,000 fragments."=20
Life is perilous for a sungrazer. The mixture of ice and dust that=20
makes up a comet's nucleus is heated like the proverbial snowball in=20
hell, and it can survive its visit to the Sun only if it is quite=20
large. What's more, the strong tidal effect of the Sun's gravity can=20
tear the loosely glued nucleus apart. The disruption that created the=20
many SOHO sungrazers was similar to the fate of Comet Shoemaker-Levy 9, =
which went too close to Jupiter and broke up into many pieces that
eventually fell into the massive planet in 1994.=20
The history of splitting gives clues to the strength of comets, which=20
will be of practical importance if ever a comet seems likely to hit the =
Earth. Also, the fragments seen as SOHO comets reveal the internal=20
composition of comets, freshly exposed, in contrast to the much-altered =
surfaces of objects like Halley's Comet that have visited the Sun many=20
times.=20
The count of SOHO's comet discoveries would be one fewer without a late =
bonus from SOHO's Solar Wind Anisotropies (SWAN) instrument, which=20
looks away from the Sun to survey atomic hydrogen in the Solar System.=20
In December 1999, the International Astronomical Union retrospectively
credited SOHO with finding Comet 1997 K2 (SOHO # 93) in SWAN full-sky=20
images from May to July 1997. It remained outside the orbit of the=20
Earth even at its closest approach to the Sun, and thus did not=20
vaporize entirely.=20
SOHO (the Solar and Heliospheric Observatory) is a mission of=20
international cooperation between NASA and the European Space Agency.=20
It is managed by the Goddard Space Flight Center for the NASA HQ office =
of Space Science.
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
(3) KAMIKAZE COMETS DON'T STAND A SNOWBALL'S CHANCE IN HELL
>From Space.com, 9 February 2000
http://www.space.com/science/astronomy/soho_comet_000209.html
By Robert Roy Britt
Senior Science Writer
If you are a comet, then you live a precarious life, alternately being
boiled by the sun and then zooming out for a deep freeze in the outer
reaches of the solar system.=20
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
(6) NEAR TO ASTEROIDS
>From SPACEDAILY, 11 February 2000
http://www.spacedaily.com/spacecast/news/near-00n.html
Arizonian Scientists Ready To Map Asteroid's Minerals
Tucson - February 10, 2000 - Monday could be a special Valentine's Day=20
for University of Arizona planetary scientists planning not just a=20
brief fling, but a year long rendezvous with Eros where they will find=20
either riches or tears.
FULL STORY AT
http://www.spacedaily.com/spacecast/news/near-00n.html
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
(7) THE TOP FACTOIDS ABOUT ASTEROIDS
>From MSNBC, Space News, 10 February 2000
http://msnbc.com/news/368661.asp?cp1=3D1
Space rocks can provide insights about Planet Earth=92s origins
By David Ropeik
MSNBC CONTRIBUTOR
=20
Feb. 10 =97 A Valentine=92s Day =93rendezvous=94 with an asteroid =
named for=20
the Greek god of love? We=92re sure this is coincidence. But the=20
yearlong study of Eros is no accident. Asteroids have a lot to teach=20
us about where we came from.
FULL STORY AT
http://msnbc.com/news/368661.asp?cp1=3D1
----------------------------------------
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