[at-l] SURPRISE METEOR SHOWER EXPECTED ON WINTER SOLSTICE

Received this from NASA.
Wildbill

Subj:   SURPRISE METEOR SHOWER EXPECTED ON WINTER SOLSTICE  
Date:   12/20/2000 2:37:56 PM Eastern Standard Time 
From:    nasanews@mail.arc.nasa.gov (NASANEWS@Ames)
To:    ames-releases@lists.arc.nasa.gov
    
    


Kathleen Burton                            Dec. 20, 2000
NASA Ames Research Center, Moffett Field, CA
(Phone:  650/604-1731 or 604-9000)
kburton@mail.arc.nasa.gov


RELEASE:  00-86AR

SURPRISE METEOR SHOWER EXPECTED ON WINTER SOLSTICE

Astronomers are forecasting a brief shower of Ursid meteors on 
Thursday night, when the Earth will hit a dense trail of dust created 
in 1405, before the birth of Columbus. Excellent viewing is predicted 
over both the United States and Canada.

Dr. Peter Jenniskens of the SETI Institute, who is based at the NASA 
Ames Research Center in the heart of California's Silicon Valley, and 
researcher Esko Lyytinen, from Helsinki, Finland, have used research 
and observation skills honed during the 1999 Leonid meteor storm to 
make the prediction.  The shower is expected to hit the Earth at 2:29 
a.m. EST on Dec. 22 (or 11:29 p.m.  PST Dec. 21).

"The normally ordinary-looking Ursids have long puzzled researchers 
because of two intense showers seen in 1945 and 1986," said 
Jenniskens. "Both of these showers lagged the passage of the comet by 
as much as 6 years.  By the time these meteors hit the Earth, the 
comet was on its way back to the outer reaches of the solar system, 
almost as far from Earth as it ever gets."

The Ursid meteors are caused by dust particles ejected from comet 
8P/Tuttle that plunge into Earth's atmosphere. The meteors appear to 
come from the constellation of Ursa Minor (the Little Bear) close by 
the pole star. In its 13.6-year orbit around the sun, comet 8P/Tuttle 
never ventures inside Earth's orbit. As a result, its meteor shower 
usually is unspectacular. It has been 6 years since the last return 
of the comet.

In a paper submitted to WGN, the journal of the International Meteor 
Organisation, Jenniskens and Lyytinen explain the 6-year lag of the 
meteor shower, and forecast this year's rich display. Once the 
meteoroids are ejected into space, they say, it takes as much as six 
centuries before their orbits are sufficiently changed by the planet 
Jupiter so they can hit the Earth. During that time, the particles 
slowly fall behind the orbiting comet that produces them.  After six 
centuries, that lag amounts to just about 6 years.

Jenniskens and Lyytinen are the first researchers to link the cycles 
of intense Ursid showers with a particular passage of comet 
8P/Tuttle.  The 1945 outburst was caused by dust shed in 1392, while 
the 1986 shower was dust from 1378, six centuries ago. The 
researchers calculate that this year, the Earth will pass the center 
of yet another trail at a distance of only halfway to the moon.

On Thursday, the Earth will find in its path the trail of dust 
ejected in 1405, they say. The shower is expected to last 2 to 3 
hours, and possibly reach rates of one meteor per minute. Many of 
these will be faint meteors, so observers are encouraged to go to a 
dark location away from city lights for best viewing.

This year's Ursids will provide an unexpected bonanza for 
astrobiologists, the scientists who study the origin, evolution, 
distribution and future of life in the universe. The shower will 
enable researchers to probe the composition and morphology of grains 
from a comet not previously sampled. Like the Leonid meteors, the 
Ursid meteoroids can be precisely dated, but they are different in 
important ways because they have spent six times longer in the solar 
system environment and plow into Earth's atmosphere with just half 
the Leonids' speed.

NASA Ames Research Center is NASA's lead center for astrobiology. 
The central administrative office of the NASA Astrobiology Institute 
(NAI), a research consortium involving academic, non-profit and NASA 
field centers, also is located at Ames. The NAI has international 
affiliate and associate members.

Futher information and a pdf file of the original paper can be found 
at http://leonid.arc.nasa.gov/leonidnews28.html

-end-



To receive Ames press releases via email, send an email with the word 
"subscribe" in subject line to: 
ames-releases-request@lists.arc.nasa.gov.
To unsubscribe, send an email to: 
ames-releases-request@lists.arc.nasa.gov with "unsubscribe" in 
subject line.  Also, the NASA Ames News Home Page at URL, 
http://amesnews.arc.nasa.gov includes news releases and JPEG images 
in AP Leaf Desk format minus embedded captions


--------------------
<fontfamily><param>Bookman</param>Kathleen Burton                            
Dec. 20, 2000    

NASA Ames Research Center, Moffett Field, CA    

(Phone:  650/604-1731 or 604-9000)

kburton@mail.arc.nasa.gov


                        

<bold>RELEASE:  00-86AR 


SURPRISE METEOR SHOWER EXPECTED ON WINTER SOLSTICE


</bold>Astronomers are forecasting a brief shower of Ursid meteors on
Thursday night, when the Earth will hit a dense trail of dust created
in 1405, before the birth of Columbus. Excellent viewing is predicted
over both the United States and Canada.   


Dr. Peter Jenniskens of the SETI Institute, who is based at the NASA
Ames Research Center in the heart of California's Silicon Valley, and
researcher Esko Lyytinen, from Helsinki, Finland, have used research
and observation skills honed during the 1999 Leonid meteor storm to
make the prediction.  The shower is expected to hit the Earth at 2:29
a.m. EST on Dec. 22 (or 11:29 p.m.  PST Dec. 21). 


"The normally ordinary-looking Ursids have long puzzled researchers
because of two intense showers seen in 1945 and 1986," said Jenniskens.
"Both of these showers lagged the passage of the comet by as much as 6
years.  By the time these meteors hit the Earth, the comet was on its
way back to the outer reaches of the solar system, almost as far from
Earth as it ever gets."


The Ursid meteors are caused by dust particles ejected from comet
8P/Tuttle that plunge into Earth's atmosphere. The meteors appear to
come from the constellation of Ursa Minor (the Little Bear) close by
the pole star. In its 13.6-year orbit around the sun, comet 8P/Tuttle
never ventures inside Earth's orbit. As a result, its meteor shower
usually is unspectacular. It has been 6 years since the last return of
the comet.


In a paper submitted to WGN, the journal of the International Meteor
Organisation, Jenniskens and Lyytinen explain the 6-year lag of the
meteor shower, and forecast this year's rich display. Once the
meteoroids are ejected into space, they say, it takes as much as six
centuries before their orbits are sufficiently changed by the planet
Jupiter so they can hit the Earth. During that time, the particles
slowly fall behind the orbiting comet that produces them.  After six
centuries, that lag amounts to just about 6 years.


Jenniskens and Lyytinen are the first researchers to link the cycles of
intense Ursid showers with a particular passage of comet 8P/Tuttle. 
The 1945 outburst was caused by dust shed in 1392, while the 1986
shower was dust from 1378, six centuries ago. The researchers calculate
that this year, the Earth will pass the center of yet another trail at
a distance of only halfway to the moon.

                    

On Thursday, the Earth will find in its path the trail of dust ejected
in 1405, they say. The shower is expected to last 2 to 3 hours, and
possibly reach rates of one meteor per minute. Many of these will be
faint meteors, so observers are encouraged to go to a dark location
away from city lights for best viewing. 


This year's Ursids will provide an unexpected bonanza for
astrobiologists, the scientists who study the origin, evolution,
distribution and future of life in the universe. The shower will enable
researchers to probe the composition and morphology of grains from a
comet not previously sampled. Like the Leonid meteors, the Ursid
meteoroids can be precisely dated, but they are different in important
ways because they have spent six times longer in the solar system
environment and plow into Earth's atmosphere with just half the
Leonids' speed. 


NASA Ames Research Center is NASA's lead center for astrobiology.  The
central administrative office of the NASA Astrobiology Institute (NAI),
a research consortium involving academic, non-profit and NASA field
centers, also is located at Ames. The NAI has international affiliate
and associate members. 


Futher information and
a pdf file of the original paper can be found at
http://leonid.arc.nasa.gov/leonidnews28.html



--- StripMime Report -- processed MIME parts ---
multipart/alternative
  text/plain (text body -- kept)
  text/html
---
* From the AT-L |  Need help? http://www.backcountry.net/faq.html  *

==============================================================================
To:            "at-lll" <at-l@backcountry.net>