Search for Extraterrestrial Life:
Past, Present, and Future
Theodore Bakanas, Graham Greene,
Alejandro Herrera, Angeline Paik and
Nathan Tan
Pre Space Age
• Ancient Greece
– Epicurus and Lucretius and other atomists believed
that the gods interference in human affairs was the
root of all evil, causing human beings to engage in all
manner of vile and foolish activities
– Solution: Eliminate religion by embracing a materialist view of the
universe
• Aristotle Rejects Cosmic Pluralism (10th Century)
and sparks new atomist movements
• Copernicus develops Heliocentric Model
Space Age and Beyond (1957-1970)
1957-1958- Sputnik Missions into Earth’s Orbit
1959- Cocconi & Morrison’s “Searching for
Interstellar Communication”- Listen at 1420
MHz (neutral hydrogen)
1960-US Pioneer 5 interplanetary probe to
Venus
1961-Drake Equation Developed- Focal Point of
SETI
1965- Mariner 4 Mission to Mars
SEL: 1970-1980
• 1971: Project Cyclops forms:
– Research teams formed
• Searched for “Earth-like radio signals”
– Budget Issues kill project
• 1973: Pioneer 10 & 11 explore asteroid belt,
Jupiter & Saturn
– First man-made object to leave the SS via
achieving escape velocity
– Contained message from Sagan & Drake
Plaque in the Pioneer Probes
SEL: 1970-1980
• 1974: Arecibo Message
– Message designed by Drake & Sagan
emitted from Arecibo telescope in Puerto
Rico
– Binary radio signal containing important
data
• Data regarding numbers, atomic numbers,
nucleotides, DNA & the depiction of a human
– Aimed at star cluster M13
SEL: 1970-1980
• 1977: Voyager Probes:
– “Voyager golden records”
• Consisted of images, greetings in various languages,
music and natural sounds
• Unlock with Hydrogen & plated with Uranium for dating
– Still extremely far
• Relying on extraterrestrial life to communicate with Earth
• Big Ear Radio – 72 second signal
– “Wow”
– No signal since
SEL: 1980-2000
• 1984: ALH 84001 Discovery
– Carbon globules
– Potential bacteria-like organism fossils
• 1992: HRMS
– High Resolution Microwave Survey
• Scanned millions of radio frequencies
• Shut down after a year – no detected signals
• 1995: 51 Pegasi b Discovery
– First extrasolar planet found in orbit around a
main sequence star
– Nearly 300 others confirmed since 2008
SEL: 1980-2000
• 1999: SETI@home
– Internet public computing project incorporating
volunteers
• Based out of UC Berkeley
– Receives data currently from Arecibo
– Sign up to volunteer your computer power/data to
be used when idle for research/computation
– Demonstrated concept of “volunteer computing”
Future of SETI
SETI Science and Technology Working
Group (SSTWG) conclusion for future
opportunities for SETI:
1. Continuous narrowband signals in the radio
2. Very short pulsed signal at optical
wavelengths
Radio Searches
• Radio telescopes that investigate the cosmos
using large radio antennas to detect nonnatural radio emissions from a location
outside our Solar System
• Current Projects:
– Project Phoenix
– SERENDIP
– SETI@home
– Allen Telescope Array
Project Phoenix
• Nine year project, finished in 2004
– Focused specifically on searching nearby planets for signs
of life
• About 800 stars in a 200 light year range
– Used a series of different radio telescopes, mainly the
Arecibo in Puerto Rico
– Scanned radio channels between .2 and 3.0 gigahertz
– resolution of 0.7 hertz per channel
– There are no naturally occurring signals at this resolution
• At the end of the project no evidence of
extraterrestrial life was found
Arecibo
SERENDIP
(Search for Extraterrestrial Radio Emissions from Nearby Developed
Intelligent Populations)
• Problem Solved – not enough telescope to go
around
• SERENDIP solves – placed an attachment on
Arecibo that operates all the time. Just looks
where the telescope is pointed.
• Theoretically should gather data 24/7
• Currently on SERENDIP V
– listens to 300 megahertz of radio channels at once
– Will have two polarizations
• Data is farmed out to SETI@home
SETI@home
• Problem solved – not enough computing
power for all that data
• How – a distributed computing effort
– Individuals at home run a program that
downloads and analyzes telescope data
– Runs while the computer is idle
• Matches the large data problem by throwing
large numbers of computers at it
Allen Telescope Array (ATA)
• Formerly known as 1 Hectare Telescope (1hT)
• Named after Paul Allen (co-founder of Microsoft)
– Funded first phase of construction (1st 42 dishes)
• Set of 350 (when, if ever completed) dishes that
combine to make essentially a 10,000m2
interferometer
– Interferometer: observed waves are superimposed to
extract information about the waves (e.g.
absorption/emission of celestial bodies, etc.)
Allen Telescope Array (ATA)
ATA Scientific Goals
• Lay the foundation of dark energy detection
• Classify 250,000 extragalactic radio sources
• Explore the transient sky and discover
new/unknown phenomena
• Survey 1,000,000 stars for SETI emmision to
detect an Arecibo strength radar out to 300 pc
• Measure molecular cloud and star formation
properties
• Plus many more
Current Status of ATA
• Construction planned in 4 stages (42, 98, 206,
350)
• First 42 dishes began operating in 2007
• April 2011, ATA suspended because of lack of
funding
• December 2011, operations resumed
Optical SETI
• Possible that alien civilizations may be using powerful
lasers (brief, nanosecond laser pulses) for interstellar
communications at optical wavelengths
• Optical SETI vs. Radio SETI
– Smaller and lighter than microwave or radio-emitting
devices
– Produce higher bandwidths and can consequently send
information faster
– Interference from natural sources of microwaves more
common
– Naturally occurring nanosecond pulses of light are most
likely nonexistent
Optical SETI Problems
1. Highly “monochromatic”: makes it
troublesome to figure out what frequency to
look for
– Emitting light in narrow pulses results in a broad
spectrum of emission, spread in frequency
becomes higher as the pulse width becomes
narrower, making it easier to detect an emission
2. Highly Directional: can easily be blocked by
clouds of interstellar dust and Earth would
cross its direct line of fire by chance
Current Optical SETI focuses
• Create an automated system to send a pulse
to targets at a constant rate
– Targets all Sun-like stars with a distance of 100
light-years
• Create an automatic laser pulse detector
system
– Detect laser flashes from civilizations attempting
contact
– Low-cost, two-meter mirror made of carbon
composite materials
Optical Pulse-Detection Systems
• Searches nearby stars to detect nanosecond optical pulsed
laser beacon signals
• Existing Programs
–
–
–
–
–
Harvard
Princeton
Sevendip: UC Berkeley
Lick Observatory
Columbus Observatory
• Numerous instances seen, but none seem to be intentional
laser signals
• Extended search for light pulses from optical to infrared
wavelengths
• All programs are being upgraded to a 3 light detector system,
making it largely immune to false alarms
All-Sky Optical SETI Survey
• Telescope looks at a stripe of sky measuring 1.6 to 0.2
degrees and reviews all stars in that stripe
– Earth’s rotation carries the celestial sphere through that stripe
• Will take 200 clear nights to survey entire visible sky
• Cherenkov radiation (light given off when charged cosmic
particles plunge through Earth’s atmosphere faster than the
speed of light in atmosphere) caused false triggers
• Recently installed:
– New electron boards that will sift data quickly, and store more
than before, allowing for false alarms to be sorted out
– Upgraded photomultiplier tube detectors that are more
sensitive and extend into the infrared