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 Orbit1959- Cocconi & Morrison’s “Searching for Interstellar Communication”- Listen at 1420 MHz (neutral hydrogen)1960-US Pioneer 5 interplanetary probe to Venus1961-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 radio2. Very short pulsed signal at optical

wavelengths

Radio Searches

• Radio telescopes that investigate the cosmos using large radio antennas to detect non-natural 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