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(meteorobs) Excerpts from "CCNet 76/2001 - 5 June 2001"
------- Forwarded Message
From: Peiser Benny <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet 76/2001 - 5 June 2001
Date: Tue, 5 Jun 2001 10:42:23 +0100
CCNet 76/2001 - 5 June 2001
---------------------------
(1) EVIDENCE OF ASTEROID BELT AROUND NEARBY STAR
Andrew Yee <ayee@nova.astro.utorontodot ca>
(2) ASTEROID BELT LIKE OURS SPOTTED AROUND ANOTHER STAR
Space.com, 4 June 2001
[...]
(5) LARGE METEORS DETECTED EXPLODING ABOVE THE PACIFIC
Environmental News Network, 4 June 2001
[...]
(7) 34 ASTROBIOLOGY POSITIONS IN SPAIN
Duncan Steel <D.I.Steel@salford.acdot uk>
[...]
======================================================================
(1) EVIDENCE OF ASTEROID BELT AROUND NEARBY STAR
>From Andrew Yee <ayee@nova.astro.utorontodot ca>
University of California-Los Angeles
Contact: =20
Harlan Lebo, hlebo@college.ucladot edu, 310- 0=20
FOR RELEASE: 9:20 a.m. PDT, June 4, 2001=20
UCLA Astronomers Identify Evidence of Asteroid Belt Around Nearby Star;
Findings Indicate Potential for Planet or Asteroid Formation=20
Identifying what may be a galactic replay of how our own solar system was
formed, UCLA astronomers have found evidence of a massive asteroid belt
around a nearby star -- findings that could indicate that planets are
forming there or have already formed.
The observations, reported June 4 at the annual meeting of the American
Astronomical Society by UCLA graduate student Christine Chen and her
advisor, Michael Jura, reveal that a star identified as zeta Leporis (HR
1998) is enveloped by swirling dust in quantities and at temperatures that
indicate a massive asteroid belt could surround the star.
"Because of the conditions we identified near zeta Leporis, we believe that
the dust around this star may contain asteroids that appear to be colliding
violently with each other," said Jura, a professor in UCLA's Department of
Physics and Astronomy. "Zeta Leporis is a relatively young star --
approximately the age of our sun when the Earth was forming. The system we
observed around zeta Leporis is similar to what we think occurred in the
early years of our own solar system when planets and asteroids were
created."
Zeta Leporis is located in the constellation Lepus (the Hare) about 70 light
years from our sun. About twice as massive as our sun, zeta Leporis is young
in astronomical terms -- about 100 million years old, compared to our sun,
which is approximately 4.5 billion years old.
"Our current findings may be just the tip of the iceberg of what we may
ultimately learn about the objects surrounding zeta Leporis," Chen said.
"In simplest terms, our planets formed when smaller objects smashed
together," she said. "Dust that surrounds a star will eventually either fall
into the star, or collide with itself and create bigger particles. The
particles we can identify around zeta Leporis may be forming chunks of rock
or larger objects; asteroids or even planets may be forming or have already
formed around zeta Leporis."
Orbiting dust around hydrogen-burning stars such as Vega, beta Pictoris and
zeta Leporis was first discovered in 1983 with the Infrared Astronomy
satellite (IRAS). The orbiting dust absorbs optical light from the central
star and is emitted as infrared. The presence of this dust around zeta
Leporis indicates that material similar to that found in our own solar
system surrounds this star.
In February Chen and Jura observed zeta Leporis with Long Wavelength
Spectrometer, an infrared camera on the 10-meter telescope at the Keck
Observatory on Mauna Kea, Hawaii. Chen and Jura found infrared-emitting dust
confined to a region smaller than 12.2 astronomical units in diameter, a
region similar in size -- in astronomical scales -- to the asteroid belt in
our solar system, which is about 5.4 astronomical units in diameter.
By observing at two infrared wavelengths, Chen and Jura estimate that the
average temperature of the dust around zeta Leporis is about 340 Kelvins
(150 F), a relatively high temperature for such material. Given this high
temperature, the grains may be as close as 2.5 astronomical units to the
star.
"There must be objects larger than dust around zeta Leporis, which may
resemble asteroids in our own solar system, that are creating the infrared-
emitting dust by violently colliding with each other," Jura said.
The discovery that the dust around zeta Leporis is unusually warm was first
published in 1991 by astronomers Hartmut Aumann and Ronald Probst.
Chen and Jura plan to confirm their findings with additional infrared
observations of zeta Leporis.
"We hope to obtain infrared spectra of the emission from zeta Leporis," Chen
said. "We want to know if the asteroids around this star are similar in
composition to objects in our solar system, and we want to learn if the
processes we now see unfolding on zeta Leporis can help us understand how
the planets in our own solar system formed."
"The next step is to get an infrared spectrum of this area, which would give
us an indication of their composition."
The research by Chen and Jura is supported by funding from NASA.
For More Information:
Ms. Christine Chen, 310-825-3172, cchen@astro.ucladot edu
Professor Michael Jura, 310-825-4302, jura@astro.ucladot edu
For illustrations of this research, go to:
http://www.astro.ucladot edu/~cchen/images/solarsystem.gif
http://www.astro.ucladot edu/~cchen/images/asteroidbelt.gif
======================================================================
(2) ASTEROID BELT LIKE OURS SPOTTED AROUND ANOTHER STAR
>From Space.com, 4 June 2001
http://www.space.com/scienceastronomy/astronomy/aas_solarsystems_010604.=
html
By Robert Roy Britt
Senior Science Writer
PASADENA, Calif. -- Astronomers announced today what they say is the first
solid evidence for solid rocks orbiting another star, an asteroid belt that
might be similar to the one surrounding our own Sun between Mars and Jupiter.
If true, the research points to the possibility of potential Earth-like
planets in the making, or planets that have been destroyed, or possibly even
a giant planet like Jupiter that, though unseen, orchestrates the chaos of
collisions that created the debris.
UCLA graduate student Christine Chen and her advisor, astronomy professor
Michael Jura, announced the findings here today at the annual meeting of the
American Astronomical Society.
"We believe we see either the remnants of planet formation or material that
may become planets," Chen said.
The scientists have not actually seen any asteroids around Zeta Leporis, a
young star twice as massive as the Sun and 60 to 70 light-years away.
Instead they have studied the temperature and position of the star's
swirling mass of debris, which they say shows evidence of chaotic collisions
among rocks that creates the dust needed to sustain such a disk.
It is a scenario similar to what is thought to have occurred during the
birth of our solar system and, to a lesser extent, continues today.
Zeta Leporis, also called HR 1998, is between 50 million and 400 million
years old, compared to our middle-aged Sun, which is about 4.5 billion years
old. Along with some other young stars, it was found in the 1980s to have a
ring of dusty debris. And in 1991 astronomers learned that this debris ring
was unusually warm and close to its parent star, unlike other disks that are
farther out, and hence colder.
This dust, given its known properties, should spiral into a star within
20,000 years, according to current theories of physics and star formation,
scientists say. But this star is much older.
"This tells us that these dust grains that we observe now were not there
when this star first formed, so they must be generated through some
secondary process such as collisions between larger objects," Chen said.
These presumed asteroids could be the size of small or large boulders,
"which collide together, and grind down, and form micron-sized grains."
The new study, funded by NASA, used the Keck Observatory in Hawaii to
examine how much light is reflected by the ring of debris, which absorbs
visible light from the star and emits it in the infrared wavelength. Similar
techniques allow scientists to estimate the composition of asteroids closer
to home. Chen and Jura determined the debris around Zeta Leporis to be, on
average, about 150 degrees Fahrenheit (65 degrees Celsius, or 340 Kelvins),
and they estimate the mass of the material to be about 1,000 times what is
found in the Asteroid Belt between Mars and Jupiter.
Chen then calculated that the ring of debris must be confined to region
between 2.5 and 12.2 astronomical units from the star. One AU is the
distance from Earth to the Sun, and the Asteroid Belt sits between Mars and
Jupiter, 1.5 and 5.2 AU from the Sun, respectively.
Echoes of our solar system
Leading models of solar system formation hold that as the Sun gathered
itself together out of a cloud of gas and dust, the leftovers settled into a
vast disk that rotated around the newborn star and gradually flattened out.
In the early years of our solar system, dust grains collided and coalesced,
and the seeds of asteroids, comets and planets were formed. The gravity of
some of the more distant protoplanets attracted gas, and Jupiter and the
other gas giants developed. These giant planets swept much of the dust disk
clean. Most of the rest of the debris spiraled in and was swallowed by the
Sun or was driven out of the solar system. But collisions still generate
some dust.
Research reported in the journal Nature in 1999 showed that these dust disks
tend to disappear when a star is about 400 million years old -- the upper
end of the age estimate for Zeta Leporis. Previously, another star was found
to have a gap in its ring of debris, hinting at planet formation.
Hinting at a planet
Dozens of planets have been found around other stars, but so far all are
giant gaseous planets very close to their host stars, leaving open the
question of how common solar systems like ours -- the habitable kind --
might be.
Mark Sykes, a Steward Observatory researcher who has studied how dust
behaves in our Asteroid Belt, speculated that the debris disk around Zeta
Leporis might have been caused by a Jupiter-sized planet that has so far
gone undetected. Such a planet would have kicked asteroids that were in
circular orbits into more elliptical ones.
Once that happens, collisions between two asteroids are no longer sideswipes
between two objects on a similar path, but instead more like cars slamming
together at an intersection.
Sykes said that the study therefore provides a possible detection method to
be used in the ongoing hunt for extrasolar planets. "In a way it's a
minor-planet and a major-planet detection system as well," he said.
Jura warned that while there could be a rocky planet, perhaps even one like
Earth, embedded in the dust, it could be a decade before any detection
techniques would be able to pick it out.
The researchers also plan to learn whether the potential asteroids around
Zeta Leporis are made up of the same stuff as the asteroids in our solar
system. If so, then the fledgling solar system around that star could serve
as an even better window to the formation of our own.
Copyright 2001, Space.com
======================================================================
(5) LARGE METEORS DETECTED EXPLODING ABOVE THE PACIFIC
>From Environmental News Network, 4 June 2001
http://www.enn.com/news/enn-stories/2001/06/06042001/nuketests_43826.asp=
Barringer Meteor Crater is a 0.8 mile diameter, 570 foot deep hole in =
the
desert located 18.6 miles west of Winslow, Arizona. Since the 1890s,
geologic studies here have played a leading role in developing an
understanding of impact processes on the Earth, the Moon and elsewhere =
in
the solar system.=20
Two large meteors entered the atmosphere above the Pacific Ocean during =
the
past nine months, said researchers at the Department of Energy's Los =
Alamos
National Laboratory who, at the time, were monitoring an infrasound =
system
set up to detect covert nuclear weapons tests.=20
Hundreds of miles from the entry points, Los Alamos researchers Rod
Whitaker, Doug ReVelle and Peter Brown heard the two meteors entering =
the
atmosphere - one on April 23 of this year and the other on August 25, =
2000.=20
The meteors were very large, measuring about six and ten feet in =
diameter.
They appeared as huge fireballs in the sky. Such large, fiery meteors =
are
called bolides, or fireballs.
The April 23 meteor plunged into the atmosphere above the Pacific Ocean
several hundred miles west of the northern Baja California region of =
Mexico.
The August 2000 meteor entered the atmosphere off the coast of =
Acapulco,
Mexico.
Based on the energy and speed of the bolides, ReVelle and Whitaker =
estimate
the first was six feet in diameter. The second meteor probably was at =
least
twice as large.
"Had anyone seen the April 23 event, they would have seen quite a =
show,"
ReVelle said. "That meteor was one of the five brightest meteors that =
have
ever been recorded. It was a very large bolide."
Bolides produce their brilliant light shows miles above Earth's =
surface.
Most meteors explode into thousands of tiny pieces or burn up =
completely
before they hit the surface.=20
When they do hit the ground, their destructive power is unmistakable. =
The
remains of a very large bolide collision with Earth can be seen at the
Barringer Meteor Crater in Arizona.
An enormous bolide fell to Earth about 35 million years ago on the =
Atlantic
coast of North America near the Delmarva Peninsula. It carved a roughly
circular crater twice the size of the state of Rhode Island, and nearly =
as
deep as the Grand Canyon. Researchers believe the impact crater =
determined
the present day location of Chesapeake Bay.=20
When a bolide enters the atmosphere - or when a large explosion such as =
a
nuclear test is detonated - it creates a sound, or pressure wave, that =
at
long range is below the levels of human hearing.
This infrasonic wave travels through the atmosphere and can be detected =
by
special microphones that are configured in an array. Los Alamos =
operates
four arrays located throughout the United States. Sandia National
Laboratory, another U.S. Department of Energy lab, monitors five arrays
located in the Pacific Northwest and western Canada.=20
By looking at the arrival time of the sounds at different array =
stations and
at the frequency of the infrasonic signal, researchers can pinpoint the
location of the source and determine the amount of energy that created =
it.
The Los Alamos researchers were using listening stations designed to =
alert
international authorities to clandestine nuclear weapons tests that may =
be
conducted by rogue groups or nations that do not abide by international
nuclear non-proliferation agreements.
Data from orbiting space platforms confirmed their observations. =
Infrared
sensors aboard U.S. Department of Defense satellites detected the =
bolide's
impact over the Pacific Ocean on April 23. The object was observed at =
an
altitude of 17.6 miles above the Earth's surface.=20
Its impact was simultaneously detected by space-based visible =
wavelength
sensors operated by the U.S. Department of Energy and by the Los Alamos
researchers monitoring their infrasound system. A similar set of
observations confirmed the entry of a meteor last August 25.
Each year a number of large meteors enter the atmosphere and are =
detected by
the Los Alamos arrays which operate in addition to satellite detection
systems. "Infrasound is very simple, inexpensive and easy to operate as =
a
backup system," said Whitaker.=20
ReVelle said that at least 10 meteors that are six feet or greater in
diameter enter the atmosphere each year. Larger bolides entering the
atmosphere occur less frequently, but they do occur nevertheless.
The meteors of April and August played an important role in improving =
the
accuracy of nuclear non-proliferation technology.
"Because those two events were detected by our four arrays and by five =
other
arrays operated by the International Monitoring System, we are able to =
use
the space platform data to calibrate our instruments, and analyses, to =
make
them better able to pinpoint the exact location where these events
occurred," Whitaker said. "Every time we hear a bolide, we learn =
something
about this technology and are better able to fine-tune it."
Whitaker said, "Infrasound arrays are listening 24 hours a day, seven =
days a
week. Sometimes other technologies miss events that infrasound arrays
detect. Consequently, infrasound is inexpensive insurance for cost =
effective
monitoring, and it is something that's available to the entire =
international
community - which isn't the case with some other technologies."
Los Alamos National Laboratory is operated by the University of =
California
for the U.S. Department of Energy's National Nuclear Security
Administration. The Los Alamos team waited until the space platform =
data
were released publicly last week before releasing their own data.=20
Copyright 2001, Environmental News Network
All Rights Reserved
======================================================================
(7) 34 ASTROBIOLOGY POSITIONS IN SPAIN
>From Duncan Steel <D.I.Steel@salford.acdot uk>
Hi Benny.
This was sent on to me by someone else. Perhaps some CCNet readers would
be interested to hear of these 34 (!) astrobiology positions in Madrid.
Cheers,
Duncan
======================================================================
======================================================================
Dear Madam/Sir,
thank you very much for your interest in our 34 Post-Doctoral =
tenure-Track
positions at Centro de Astrobiologia.
Enclosed you will find one document describing the offer we are making, =
and
another one describing the steps to be followed. Read both carefully =
and act
quickly because the timelines are very short. From the time when you =
submit
your documents to CAB (deadline June 10th) to the time when you submit =
to
the Ministry of Science and Technology, you should spend your time
finilizing the FULL research project that you propose. Note that in =
June
10th you are requested to send to rycdot cab@inta.es ONLY the letters of
recommendation (in the format provided at one the web addresses we give
you), your vitae and the 300 word SUMMARY of your project.
All relevant web addresses are given in the advertisement, which is a
Microsoft Word document (sorry!).
We apologize for the short times available, but that is beyond our
control.
We wish you very good luck and thank you very much for your interest in =
our
Center, in working with us and in pursuing an Astrobiology career.
Sincerely,
Juan Perez-Mercader
P.s.: Use the e-mail address <rycdot cab@inta.es> for any correspondence =
with
CAB on this matter.
Post Doctoral Tenure-track Positions
in the framework of the "Ram=F3n y Cajal Program" of the Ministerio de
Ciencia y Tecnolog=EDa of Spain
The Centro de Astrobiolog=EDa (CAB) invites applications by qualified
candidates for 5 year tenure-track positions in Astrobiology. These 34
positions are new and the successful candidates will have to join CAB =
from
the late Fall of 2001 to early Winter of 2002. The positions are at the
Centro de Astrobiolog=EDa, in its brand new facility in the Campus of =
INTA,
Torrej=F3n de Ardoz, Madrid, and will be granted together with some =
seed money
to allow beginning of research activities immediately upon filling the
position. These positions are part of the "Ram=F3n y Cajal Program" of =
the
Ministry of Science and Technology of Spain (www.
mcyt.es/cajal/default.htm).
We are looking for enthusiastic persons with postdoctoral experience, =
highly
motivated and interested in working within a multidisciplinary =
scientific
environment. Successful candidates will be expected to engage in =
existing
research programs as well as in new collaborative research carried out =
at
the Center and within the framework of our association to the NASA
Astrobiology Institute of which the CAB is, at present, the only
international Associate Member.
The areas of specialization of the applicant include the following:
Astronomy and Astrophysics, Planetary Geology and Earth Sciences, =
Physical
Chemistry and Cosmogeochemistry, Molecular Evolution, Genomics and
Proteomics, Paleobiology, Extremophiles, Complexity and Non-linear =
Science,
Numerical Simulation and Supercomputation, Robotics and Advanced =
Internet
Communications, and Instrumentation for Astrobiology.
Details about the "Ramon y Cajal Program" at Centro de Astrobiolog=EDa =
are
available at wwwdot cab.inta.es
Those interested are invited to contact the CAB by e-mail at
rycdot cab@inta.es, telephone (34-91-520-1111) or fax (34-91-520-1621).
The deadline for presentation of application materials at CAB is June =
15th,
2001, and at the Ministry of Science and Technology June 23rd, 2001. =
Both
steps are mandatory.
Committed to Equal Opportunities for All
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