SETI

New Search for Signals from 20,000 Star Systems Begins

MOUNTAIN VIEW – The SETI Institute has inaugurated a greatly expanded hunt for deliberately produced radio signals that would indicate the presence of extraterrestrial intelligence.  Over the course of the next two years, it will scrutinize the vicinities of 20,000 so-called red dwarf stars. 

Allen Telescope Array

“Red dwarfs – the dim bulbs of the cosmos – have received scant attention by SETI scientists in the past,” notes Institute engineer Jon Richards.  “That’s because researchers made the seemingly reasonable assumption that other intelligent species would be on planets orbiting stars similar to the Sun.”

This conservative assessment was bolstered by the argument that few planets were likely to be found in the habitable zone of a red dwarf star, simply because that zone is far narrower than for brighter stars like the Sun. Additionally, any worlds that were in this zone would be orbiting so close to their suns that they would quickly become tidally locked – with one hemisphere perpetually facing the star.  It was assumed that this would produce a planet that was intolerably hot on one side, and brutally cold on the other, ruling it out as an abode for life. 

However, more recent research has indicated that, if these worlds have oceans and atmospheres, heat would be transported from the lit side to the dark, and a significant fraction of the planet would be habitable.  In addition, exoplanet data have suggested that somewhere between one sixth and one half of red dwarf stars have planets in their habitable zones, a percentage comparable to, and possibly greater, than for Sun-like stars.

“Significantly, three-fourths of all stars are red dwarfs,” notes SETI Institute astronomer Seth Shostak.  “That means that if you observe a finite set of them – say the nearest twenty thousand – then on average they will be at only half the distance of the nearest twenty thousand Sun-like stars.”

Closer stars mean that any signals would be stronger.

Also, red dwarfs burn for a period of time that’s greater than the current age of the universe: every red dwarf ever born is still shining today.  They are, on average, billions of years older than stars than Sun-like stars.

“This may be one instance in which older is better,” Shostak says.  “Older solar systems have had more time to produce intelligent species.” 

The search is being conducted on the SETI Institute’s Allen Telescope Array, located in the Cascade Mountains of northern California.  This grouping of 42 antennas can currently observe three stars simultaneously.

“We’ll scrutinize targeted systems over several frequency bands between 1 and 10 GHz,” says Institute scientist Gerry Harp.  “Roughly half of those bands will be at so-called ‘magic frequencies’ – places on the radio dial that are directly related to basic mathematical constants.  It’s reasonable to speculate that extraterrestrials trying to attract attention might generate signals at such special frequencies.”

The new red dwarf survey is planned to take two years.  Targets are being chosen from a list of approximately 70,000 red dwarfs compiled by Boston University astronomer Andrew West.  The search will also incorporate relevant new data as generated by NASA’s TESS (Transiting Exoplanet Survey Satellite) project, which will examine nearby stars, including red dwarfs, for planets.

 

Research Thrust: 

Looking For Deliberate Radio Signals From KIC 8462852

MOUNTAIN VIEW — Could there be intelligent life in the star system KIC 8462852?  A recent analysis of data collected by the Kepler space telescope has shown that this star, informally known as Tabby’s Star, evidences aperiodic dimming of 20 percent and more.  While several natural explanations for this strong change in luminosity have been proposed, one possibility is that a technologically adept civilization has built megastructures in orbit around star, causing the dimming. 

One example of a large-scale astroengineering project would be the construction of a so-called Dyson swarm of solar panels for large-scale energy collection.  Other possible structures include artificial space habitats, or a planet-size or larger occulting object intended to provide a long-lasting signal to other galactic inhabitants.

In order to investigate the possibility of a deliberate cause of KIC 8462852’s unusual behavior, the SETI Institute has trained its Allen Telescope Array on this star for more than two weeks.  The Array consists of 42 antennas, each 6 meters in size, and is located approximately 500 km north of San Francisco in the Cascade Mountains.

Two different types of radio signals were sought: (1) Narrow-band signals, of order 1 Hz in width, such as would be generated as a “hailing signal” for societies wishing to announce their presence. This is the type of signal most frequently looked for by radio SETI experiments.  (2) Broad-band signals that might be due to beamed propulsion within this star system.  If astroengineering projects are really underway in the vicinity of KIC 8462852, one might reasonably expect the presence of spacecraft to service this activity.  If these craft are propelled by intense microwave beams, some of that energy might manifest itself as broad-band radio leakage.

“This is the first time we’ve used the Allen Telescope Array to look for relatively wide-band signals, a type of emission that is generally not considered in SETI searches,” said SETI Institute scientist Gerry Harp. 

Analysis of the Array data show no clear evidence for either type of signal between the frequencies of 1 and 10 GHz.  This rules out omnidirectional transmitters of approximately 100 times today’s total terrestrial energy usage in the case of the narrow-band signals, and ten million times that usage for broad band emissions. 

While these limits are relatively high – a fact due primarily to the large distance (>1400 light-years) of KIC 8462852 – one should note the following: (1) The required transmitter power for the narrow-band signals could be reduced enormously if the signal is being deliberately beamed in our direction.  (2) Microwave propulsion schemes would undoubtedly be beamed as well, and that would also reduce the minimum transmitter power necessary for detection by the Array. 

Finally, note that any society able to build a Dyson swarm would have access to energy at a level approaching 1027 watts.  Even omnidirectional transmitters would be detectable if only a tiny percentage of this energy were used for signaling.

“The history of astronomy tells us that every time we thought we had found a phenomenon due to the activities of extraterrestrials, we were wrong,” notes Institute astronomer Seth Shostak.  “But although it’s quite likely that this star’s strange behavior is due to nature, not aliens, it’s only prudent to check such things out.” 

Observations will continue, but so far no evidence of deliberately produced radio signals has been found in the direction of KIC 8462852.

This work can be found at http://arxiv.org/abs/1511.01606

Research Thrust: 

WILLIAM BORUCKI RECEIVES SETI INSTITUTE’S 2015 DRAKE AWARD

Bill Borucki

MOUNTAIN VIEW — On October 15, the SETI Institute will award the 2015 Frank Drake Award for Innovation in SETI and Astrobiology Research to William Borucki, who was the Principal Investigator for NASA’s Kepler mission.  

Borucki will be honored for leading a team that conceived, designed, built and operated a space telescope that has detected dozens of possible Earth-size worlds situated in the habitable zone, the range of distances from a star where liquid water might exist on a planet’s surface.  Fifteen of these worlds have been verified and double that number await confirmation, although scientists do not know if they harbor life.

“The Frank Drake Award for Innovation in SETI and Life in the Universe Research honors distinguished contributors to the search for life beyond Earth,” said Bill Diamond, President and CEO of the SETI Institute.  “Awardees are chosen by a panel of scientists who are appointed by the SETI Institute Board of Trustees.  There are few developments more important to the quest for life beyond Earth than the new worlds discovered by the Kepler mission.”

In total, the Kepler mission has so far discovered more than one thousand confirmed exoplanets, and 3,600 additional candidates are awaiting verification.  More than half of all the known exoplanets have been found by this spacecraft.

Borucki is the third recipient of the Drake Award, which was launched in 2001 with a ceremony honoring its namesake.  Frank Drake conducted a pioneering search for signals from extraterrestrial intelligence in 1960, and a year later developed a simple equation that can be used to estimate the prevalence of technically sophisticated societies in the Milky Way.  

The award was also given to Charles Townes, a physicist who won the Nobel Prize for his work on developing the first masers and lasers.  Townes was also a champion of so-called optical SETI, a scheme in which mirror-and-lens telescopes are used to hunt for brief pulses of light that could be signals from other worlds.

“Kepler has been hugely successful in determining that there must be several billion terrestrial planets in the habitable zone of solar-like stars,” says Borucki.  “The knowledge that our galaxy is filled with planets, but that the SETI Program has not heard from anyone is intriguing; so which factor in the well-known Drake equation accounts for the missing communications?  Clearly, the continuation of the search is critical to understanding mankind’s position in the universe.”

Borucki, who has been a space scientist at NASA’s Ames Research Center since 1962, has degrees in physics from the University of Wisconsin, Madison, as well as a masters in meteorology from San Jose State University.  His early research helped to design the heat shields for the Apollo Mission re-entry vehicles.  He also measured lightning activity on other planets.

In the early 1980s, Borucki began to study the feasibility of detecting exoplanets using the so-called transit method.  This requires sensing the very slight (typically 0.01 percent for an Earth-size planet) dimming of a star that occurs as planet passes in front of it. Eventually, Borucki concluded that it would be possible to measure such slight dimming with an orbiting telescope. After years of persistent application to NASA, the Kepler spacecraft – designed to survey 150,000 stars – was launched in 2009.  It is arguably one of the most successful astronomical instruments of all time, and clearly relevant to SETI research because it addresses the question of what fraction of stars has habitable planets.

The award will be presented at a private function hosted by the SETI Institute.

Research Thrust: 

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