EXTRATERRESTRIAL LIFE
Introduction
There is no evidence of extraterrestrial
life now, but astronomers valiantly continue the search.
This quest is called SETI, for Search for
Extra Terrestrial Intelligence. Most SETI projects use radio telescopes
to listen for radio signals from planets in distant star systems.
The Arecibo telescope in Puerto Rico is
the largest radio telescope in the world. It has a hemisphere
shape with a diameter of 305 meters (1000 feet) at its brim. It
focuses incoming electromagnetic waves onto a feed arm.
Proponents
Noted author Carl Sagan (1934 - 1996) was
one of the leading proponents of SETI.
Astronaut Buzz Aldrin is also a proponent.
He proposed building a radio telescope on the dark side of the
Moon. Such a telescope would be shielded from Earth's radio signals.
Project OZMA
Radioastronomer Frank D. Drake carried
out the first attempt to detect interstellar radio transmissions,
in 1960. He performed this at the National Radio Astronomy Observatory
(NRAO) in Green Bank, West Virginia,
Project Ozma was named after the queen
of L. Frank Baum's imaginary land of Oz -- a place "very
far away, difficult to reach, and populated by strange and exotic
beings." The stars chosen by Drake for the first SETI search
were Tau Ceti in the Constellation Cetus (the Whale) and Epsilon
Eridani in the Constellation Eridanus (the River), some eleven
light years (66 trillion miles) away. Both stars are about the
same age as our sun.
Project HRMS
As of 1992, NASA was conducting a SETI
project called HRMS, for High Resolution Microwave Survey. This
was one of several NASA SETI projects. Congress terminated SETI
funding in 1993 due to budget pressures, however.
Project Phoenix
Another SETI project is called Project
Phoenix. This is a privately funded continuation of the NASA HRMS
project. This project will use the Arecibo radio telescope along
with others throughout the world. Its strategy is to carefully
examine the regions around 1,000 nearby Sun-like stars.
Project Phoenix began its serach using the Parkes 210 foot radio
telescope in New South Wales, Australia. This is the largest radio
telescope in the Southern Hemisphere. Project Phoenix also uses
the Arecibo telescope.
Project Beta
BETA, for Billion-channel Extra-Terrestrial
Assay, is another SETI project. This search is performed using
the Harvard-Smithsonian radio telescope outside of Boston. Incoming
radio waves are fed into a super computer for analysis.
Project SERENDIP
The University of California at Berkeley
SETI program, named SERENDIP, was begun in the late 1970's. This
project is aimed at detecting narrow band radio signals from extraterrestrial
civilizations. It collects data using the Arecibo telescope.
Seti@Home
SETI@home is a scientific experiment that
harnesses the power of hundreds of thousands of Internet-connected
computers in the search for extraterrestrial intelligence. The
data is collected from the Arecibo Radio Telescope in Puerto Rico.
This project is being conducted by the SETI Institute in Mountain
View, California.
People interested in participating can download software at:
Optical SETI
Some astronomer believe that extraterrestrial
worlds might try to communicate with bursts of laser light.
Stuart Kingsley, an amateur astronomer, has an observatory in
Columbus, Ohio dedicated to the search for optical signals.
Astronomer Dan Werthimer of the University of California at Berkeley
is involved in a similar search using the Leuschner Observatory.
Paul Horowitz, a Harvard astronomer, is also searching for optical
signals.
Planets outside of Our Solar System
A number of planets outside our solar system
have recently been discovered.
Astronomers Michel Mayor and Didier Queloz
of the Geneva Observatory discovered a planet orbiting the star
51 Pegasi, which is in the constellation Pegasus. This star is
42 light-years from the Earth. The discovery was announced in
October 1995.
In addition, San Francisco State University
astronomers Geoffrey Marcy and Paul Butler have discovered a planet
orbiting the star 47 Ursae Majoris. This star is in the Big Dipper
and is 34 light-years away from the Earth. The discovery was made
on December 30, 1995.
Marcy and Butler have also discovered a
planet orbiting the star 70 Virgins, which in the constellation
Virgo. This star is also 34 light-years away from the Earth. Note
that some astronomers consider that this new "planet"
is really a brown dwarf star.
As new planets are discovered, astronomers
will investigate the temperature and chemical composition of each.
These parameters will help determine whether the new planets are
capable of sustaining life. The various SETI projects can then
choose whether to focus their radio telescopes on these new planets.
References
1. Michael Milstein, Signs of Light, Smithsonian
Air & Space Magazine, September 1999.
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