BLC1

BLC1 (Breakthrough Listen Candidate 1) was a candidate SETI radio signal detected and observed during April and May 2019, and first reported on 18 December 2020, spatially coincident with the direction of the Solar System's closest star, Proxima Centauri.[1][2][3]

Parkes Observatory that detected BLC-1

Signal

The apparent shift in its frequency, consistent with the Doppler effect, was suggested to be inconsistent with what would be caused by the movement of Proxima b, a planet of Proxima Centauri.[4][5] The Doppler shift in the signal was the opposite of what would be expected from the Earth's spin, in that the signal was observed to increase in frequency rather than decrease.[6] Although the signal was detected by Parkes Radio Telescope during observations of Proxima Centauri, due to the beam angle of Parkes Radio telescope, the signal would be more accurately described as having come from within a circle roughly 16 arcminutes (approximately 1/4 of a degree, half the angular width of Earth's moon) in angular diameter, containing Proxima Centauri,[6] so the signal could have originated elsewhere in the Alpha Centauri system.[7] The signal had a frequency of 982.002 MHz.[4]

The radio signal was detected during 30 hours of observations conducted by Breakthrough Listen through the Parkes Observatory in Australia in April and May 2019.[8][9] As of December 2020, follow-up observations had failed to detect the signal again, a step necessary to confirm that the signal was a technosignature.[10]

Origin

A paper by other astronomers released 10 days before the news report about BLC1 reports the detection of "a bright, long-duration optical flare, accompanied by a series of intense, coherent radio bursts" from Proxima Centauri also in April and May 2019. Their finding has not been put in direct relation to the BLC1 signal by scientists or media outlets as of January 2021 but implies that planets around Proxima Centauri and other red dwarfs are uninhabitable for humans and other currently known organisms.[11][12][13]

In February 2021, a new study proposed that, as the probability of a radio-transmitting civilization emerging on the Sun's closest stellar neighbour was calculated to be approximately 10−8, the Copernican principle made BLC1 very unlikely to be a technological radio signal from the Alpha Centauri System.[14]

On 25 October 2021, researchers published two studies concluding that the signal could be human radio interference.[15]

See also

References
  1. Drake, Nadia (2020-12-18). "Alien hunters detect mysterious radio signal from nearby star". National Geographic. Retrieved 2020-12-19.
  2. Whitwam, Ryan (2020-12-23). "Astronomers Spot Potentially Artificial Radio Signal From Nearby Star". ExtremeTech. Retrieved 2020-12-23.
  3. Marchis, Franck (December 21, 2020). "Did Proxima Centauri Just Call to Say Hello? Not Really!". SETI Institute. Retrieved 2020-12-23.
  4. Billings, Jonathan O'Callaghan,Lee. "Alien Hunters Discover Mysterious Signal from Proxima Centauri". Scientific American.{{cite web}}: CS1 maint: multiple names: authors list (link)
  5. Sample, Ian (2020-12-18). "Scientists looking for aliens investigate radio beam 'from nearby star'". The Guardian. Retrieved 2020-12-19.
  6. Wright, Jason (20 December 2020). "BLC1: A candidate signal around Proxima". AstroWright. Pennsylvania State University.
  7. "Why Radio Signal BLC1 Could be from Extraterrestrial Life Other Than on Exoplanet Proxima Centauri B". 12 April 2022.
  8. Overbye, Dennis (2020-12-31). "Was That a Dropped Call From ET? - A spooky radio signal showed up after a radio telescope was aimed at the next star over from our sun". The New York Times. Retrieved 2020-12-31.
  9. "Breakthrough Initiatives". breakthroughinitiatives.org. Retrieved 2020-12-19.
  10. Frank, Adam (2020-12-31). "A new frontier is opening in the search for extraterrestrial life - The reason we haven't found life elsewhere in the universe is simple: We haven't really looked until now". The Washington Post. Retrieved 2021-01-01.
  11. University of Sydney (December 9, 2020). "Space weather discovery puts 'habitable planets' at risk". Phys.org. Retrieved 22 January 2021.
  12. Anderson, Paul Scott (December 23, 2020). "Space weather in Proxima's vicinity dims hopes of habitable worlds". EarthSky.org. Retrieved 2021-01-22.
  13. Zic, Andrew; Murphy, Tara; et al. (2020). "A Flare-type IV Burst Event from Proxima Centauri and Implications for Space Weather". The Astrophysical Journal. 905 (1): 23. arXiv:2012.04642. Bibcode:2020ApJ...905...23Z. doi:10.3847/1538-4357/abca90. S2CID 227745378. Retrieved 2021-01-22.
  14. Siraj, Amir; Loeb, Abraham (2021-01-11). "The Copernican Principle Rules Out BLC1 as a Technological Radio Signal from the Alpha Centauri System". arXiv:2101.04118 [physics.pop-ph].
  15. Choi, Charles Q. (2021-10-26). "Mysterious radio signal from Proxima Centauri was definitely not aliens". Space.com. Retrieved 2021-10-29.
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