If aliens are synchronizing their signals with the light from supernova 1987A, then search for extraterrestrial intelligence (SETI) is handling the case. Scientists at the institution say they can find such signals by looking for them in a place called the “SETI Ellipsoid”.
About 167,600 years ago, a blue supergiant star exploded. supernova inside Large Magellanic Cloudwhich is a small satellite the galaxy neighboring ours Milky Way. The light emitted from this supernova passed quickly space -most 299,792,458 meters per second (186,282 miles per second).
It later reached the following point on February 24, 1987: Soil.
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The supernova became known as SN 1987A, and its light did not stop on Earth. It continued to move deeper into our galaxy, where other alien life could be glimpsed. This is where the concept of the SETI Ellipsoid comes from. It is described as an elliptical-shaped volume with Earth at one focus and SN 1987A at the other; Its circumference indicates where there is enough time for supernova light to reach a star and for any technological life on a planet orbiting that star to send a signal that will reach us now.
The idea here is that we can use the SETI ellipsoid as a concept related to game theory, known as a Schelling point. This defines a focal point of sorts around which two protagonists (in this case, the transmitting aliens and the human astronomers monitoring or listening to their signals) can coordinate their activities without announcing their intentions. If that sounds complicated, consider that SETI has been using Schelling points since Frank Drake’s Project Ozma, the first SETI search conducted in April and May 1960. Drake looked for radio signals at the iconic 21-centimeter hydrogen wavelength because he thought aliens would notice that our astronomers routinely look at this wavelength. He reasoned that transmitting at such a commonly used wavelength would increase the chances of the signal being detected.
“As Dr. Jill Tarter often points out, SETI searches are like looking for a needle in a 9-D haystack,” said Sofia Sheikh of the SETI Institute and the University of California, Berkeley. expression. “Any technique that can help us prioritize where to look, like the SETI Ellipsoid, can give us a shortcut to the most promising parts of the haystack.”
The hope is that technological aliens who see SN 1987A will synchronize their signals with it, knowing that we will look for it in the SETI Ellipsoid. But the problem was that until very recently it was impossible to search for the ellipsoid with reasonable accuracy.
To understand why, let’s take a look at some SETI and the history of astronomy.
The SETI Ellipsoid concept is not new. It was first described by TB Tang in the Journal of the British Interplanetary Society in 1976, and independently by Soviet astronomer PV Makovetskii in 1977. At that time there was no obvious target on which to base the SETI Ellipsoid; Makovetskii suggested using Nova Cygni 1975; white dwarf collect items from friends red dwarf The star caused the system to brighten significantly for about a week.
After the discovery of SN 1987A, Hungarian astronomer Iván Almár realized that it created a new SETI Ellipsoid object, and in 1994 Argentinian astronomer Guillermo Lemarchand described a search using this ellipsoid. However, uncertainties in distances stars the parts near the periphery of the ellipsoid were very large. Uncertainties in distance correspond to uncertainties in distance. time; If we get even half the distance to a star wrong light yearFor example, this means our search for synchronized signals will be six months sooner or later. And in these technosignature hunts, timing can be everything.
Only in the last decade, with the advent of the European Space Agency’s Gaia mission, which aims to measure the positions and properties of a billion stars, astronomers have begun to collect the distances of stars with the necessary accuracy to search for the SETI ellipsoid of SN 1987A. So a team led by James Davenport of the University of Washington in Seattle combined Gaia data with stars on the SETI Ellipsoid located in the Continuous Imaging Region of NASA’s Transiting Exoplanet Survey Satellite (TESS).
TESS spends a year looking at each celestial hemisphere and divides those hemispheres into sectors. TESS examines each sector and monitors exoplanet transits for 27 days before moving on to the next sector. However, there is a region around each celestial pole that is visible in every sector. This is the Continuous Viewing Zone; TESS collects data from here for a year.
Davenport’s team detected 32 stars in the Continuous Imaging Region on the SETI Ellipsoid, and the annual data provide some leeway in case there is ongoing uncertainty in their distances. Being an optical telescope, TESS can only detect optical signals, not radio messages. Davenport’s team examined the light of 32 stars during that year, looking for any anomalies that might indicate a technological signature. These anomalies could include a flare from a laser signal, an unusual passage from an artificial structure, or even an artificial burst that mimics the light curve of SN 1987A. In 1994, Lemarchand proposed looking for a “pseudo-pulsar” signal; because the aliens might have known that astronomers would be looking for a star signal. pulsar He was born in the fire of the supernova. (No pulsar has been detected in SN 1987A to date.)
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Suffice it to say that Davenport’s team found no anomalies, so no evidence of aliens was detected. But the SETI Ellipsoid is always growing (at the speed of light, in fact) and will move towards other stars in the future.
Approaching PANOSETI The (Panoramic SETI) project, which will continuously observe the entire sky visible from the Lick Observatory in California and look for optical and near-infrared laser signals, will be perfect for investigating the SETI Ellipsoid. Vera C. Rubin Observatory Its launch in Chile by the end of this decade could be a game changer.
“New surveys of the sky offer groundbreaking opportunities to search for technosignatures coordinated with supernovae,” co-investigator Bárbara Cabrales from Smith College in the United States said in the statement. said.
Analysis of the SETI Ellipsoid and results from stars in TESS’s Continuous Imaging Region were announced last year. Astronomy Magazine.