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SETI

April 6, 2020

There's a joke about the search for extraterrestrial intelligence (SETI) - We shouldn't waste time looking for it until we see some sign of intelligent life on Earth. One problem faced by SETI researchers is the lack of government funding. SETI has received no government funding in the United States since 1993. One possible reason for this is that some religious groups are threatened by the idea that the genesis of life on Earth was not a special event. Another problem is that the SETI concept itself is a matter of faith.

The faith part of SETI is codified in the much criticized Drake equation that estimates the probability of the occurrence of a detectable extraterrestrial intelligence. Encoded in this equation is the idea that small numbers for such factors as the fraction of stars that have planets, the fraction of planets on which life arises, and the fraction that choose to communicate their existence, are balanced by the large number of stars in our galaxy. The number of stars in our Milky Way galaxy is estimated to be between 100 and 400 billion.

Figure caption

Frank Drake, April 11, 2019.

In 1960, Drake listened for intelligent radio signals for 150 hours from the two nearby stars, Tau Ceti and Epsilon Eridani, using a 26 meter radio telescope at the National Radio Astronomy Observatory, Green Bank, West Virginia.

He examined a small bandwidth around the "water hole," the 1.420 gigahertz (21 cm wavelength) emission line of interstellar hydrogen.

This frequency is thought to be an obvious place for communications when no standard communications frequencies are known, since hydrogen is the most abundant element in the universe. Hydrogen is also a component of water, which is essential to life on Earth.

(Portion of a Wikimedia Commons photo by Steve Jurvetson)


A major problem with a radio approach to SETI is that an advanced civilization may have moved from radio to a more advanced communication technology that's unknown to us. Radio has been known to humans for less than 150 years, and its limitations have inspired other communication technologies, such as lasers. Fifty years ago, the world communicated using radio. Today, the Internet is enabled by light signals in fiberoptic cables. Our descendants might one day compare their communication technology to radio in the same way that we compare radio to smoke signals. There's also the idea that, like us, others might just be listening and not transmitting. The cost of transmission is orders of magnitude greater than that of listening.

In the absence of government funding, private donations, especially from the largesse of some wealthy individuals, have kept SETI alive. Paul Allen (1953-2018), a founder of Microsoft, donated millions of dollars to the establishment of the Allen Telescope Array at the Hat Creek Radio Observatory of the SETI Institute (Mountain View, California). I wrote about the Allen Telescope Array in an earlier article (Allen Telescope Array, April 26, 2011).

Russian physicist and entrepreneur, Yuri Milner, has donated $100 million for the Breakthrough Listen initiative that includes an optical SETI component. This initiative buys time on existing radio telescopes in its SETI search. There's a website for Breakthrough Listen at the Berkeley SETI Research Center.

Portion of the Very Large Array

The Very Large Array (VLA), a portion of which is shown, was completed in 1980.

The dish antennas are mounted on railroad tracks in a "Y" pattern to adjust placement for interferometry at different wavelengths.

(Wikimedia Commons photo by CGP Grey. Click for larger image.)


The Very Large Array (VLA), a component of the National Radio Astronomy Observatory (NRAO), is an impressive assemblage of twenty-eight 25-meter dish antennas on a desert plain near Socorro, New Mexico. Shortly after its completion, it was used in a scene of the 1984 film, "2010: The Year We Make Contact," the sequel to the film, "2001: A Space Odyssey."

The SETI Institute and NRAO have recently announced a collaboration to use the VLA for SETI research.[1-3] A new system called the Commensal Open-Source Multimode Interferometer Cluster Search for Extraterrestrial Intelligence (COSMIC SETI) will allow the VLA to continually look for SETI signals.[1-3] COSMIC will take data from each VLA antenna from the same data stream used for other VLA research and stream it through a parallel ethernet interface to provide much more SETI data than obtained earlier.[1-2] Says Tony Beasley, Director of the NRAO,
"Determining whether we are alone in the universe as technologically capable life is among the most compelling questions in science, and NRAO telescopes can play a major role in answering it."[1]

The data from the COSMIC ethernet interface will be analyzed by signal processing software in a search for technosignatures, the incidental electromagnetic emissions of a technologically advanced, extraterrestrial civilization.[1] This SETI research will be conducted in parallel with VLA's 5-year Sky Survey, which will survey 75% of the entire sky, everything that can possibly be viewed from the VLA location.[1] The development of the COSMIC interface was funded by a gift from John Giannandrea, a Trustee of the SETI Institute, and his spouse, Carol.[1-2] As typical, no government money is involved.[1]

Beasley, speaking at the 2020 American Association for the Advancement of Science (AAAS) meeting (Seattle, Washington, February 13-16), said that it's "time for Seti to come in from the cold and be properly integrated to all other areas of astronomy".[3] It's estimated that the COSMIC initiative will increase the chances of finding intelligent life by one, or two, orders of magnitude.[3] The UK's Astronomer Royal, Sir Martin Rees, noting that a SETI research expenditure is minuscule compared with "Big Science" projects, is quoted by the BBC in saying,
"I'd feel far more confident arguing the case for Seti than for a particle accelerator... Seti searches are surely worthwhile, despite the heavy odds against success, because the stakes are so high".[3]

In other SETI news from the AAAS meeting, the Breakthrough Listen Initiative released nearly 2 petabytes of data on February 14, 2020, from an extensive search for cosmic radio emissions from the Milky Way.[4] A previous data release of a petabyte of radio telescope and optical telescope data was released in June, 2019.[4] About half of the radio data cover wavelengths from 1-12 gigahertz collected from the Parkes radio telescope in Parkes, New South Wales, Australia.[4] The Parkes location is able to observe the entire galactic disk and galactic center.[4] The other half was from NRAO's Green Bank Observatory in Green Bank, West Virginia.[4] Breakthrough Listen also released observations of the interstellar comet 2I/Borisov.[4]

Comet 2I/Borisov at perihelion, December 12, 2019

A photograph of interstellar comet 2I/Borisov at perihelion, December 12, 2019

The comet was 298 million kilometers from Earth in this photo. Comet 2I/Borisov was only the second interstellar object detected in our Solar System.

(Image by NASA, ESA, and D. Jewitt (UCLA) via Wikimedia Commons.)


One search, lead by Sofia Sheikh of Penn State University, looked for radio emissions from twenty nearby stars that are aligned with Earth's orbital plane.[5] Any extraterrestrials on planets around those stars would know of Earth's existence, since they could see Earth pass in front of the Sun using their telescopes.[5] The search was done using NRAO's Green Bank Telescope in West Virginia operating at billions of frequencies between 4 and 8 gigahertz.[4-5]

The data collection strategy involved looking for radio emission from each star for five minutes, collecting signals away for five minutes, and repeating this pairing twice again.[4] There were several hundred positives from this search, but all these were Earth-based or satellite-based human interference.[4] As Sheikh explains,
"If other civilizations have telescopes like ours, they would know that the Solar System has planets from their transits, and even know that Earth has life. That is how we have discovered thousands of other exoplanets, so it kind of makes sense to extrapolate and say that that might be how other intelligent species find planets as well. And if they know we're here, they might be signaling us.[5] My search was sensitive enough to see a transmitter basically the same as the strongest transmitters we have on Earth, because the targets were nearby... So we know that there isn't anything as strong as our strongest radars beaming something at us."[4-5]

One new SETI concept is the idea of galactic centers being so-called Schelling points; that is, an obvious place to look when you don't know where to look.[6] The first such Schelling point was the previously mentioned hydrogen emission line. The galactic center is certainly the most interesting part of the Milky Way galaxy. A radio beacon placed there could be powered by its central four million solar mass black hole.[4-6]

References:

  1. SETI Institute and National Radio Astronomy Observatory Team Up for SETI Science at the Very Large Array, SETI Institute Press Release, February 13, 2020.
  2. NRAO, SETI Institute Agree on New Research Programs, NRAO Press Release, February 15, 2020.
  3. Pallab Ghosh, "Astronomers want public funds for intelligent life search," BBC News, February 15, 2020.
  4. Robert Sanders, "Breakthrough Listen scans Milky Way Galaxy for beacons of civilization," University of California Berkeley Press Release, February 14, 2020.
  5. Looking for aliens who might be looking for us, Penn State University Press Release, February 14, 2020,
  6. Sarah Knapton, "Aliens might have placed beacon in centre of Milky Way, say scientists," Telegraph (UK), February 14, 2020.

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