BLC1 (''

Breakthrough Listen Breakthrough Listen is an astronomy project to search for intelligent extraterrestrial communications. With $100 million in funding and thousands of hours of dedicated telescope time on state-of-the-art facilities, it is the most comprehensive se ...

Candidate 1'') was a candidate

SETI Seti or SETI may refer to: Astrobiology * SETI, the search for extraterrestrial intelligence. ** SETI Institute, an astronomical research organization *** SETIcon, a former convention organized by the SETI Institute ** Berkeley SETI Research Cent ...

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 neighboring star,

Proxima Centauri Proxima Centauri is the nearest star to Earth after the Sun, located 4.25 light-years away in the southern constellation of Centaurus. This object was discovered in 1915 by Robert T. A. Innes, Robert Innes. It is a small, low-mass st ...

Signal

The apparent shift in its frequency, consistent with the

Doppler effect The Doppler effect (also Doppler shift) is the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave. The ''Doppler effect'' is named after the physicist Christian Doppler, who described ...

, was suggested to be inconsistent with what would be caused by the movement of

Proxima b Proxima Centauri b is an exoplanet orbiting within the habitable zone of the red dwarf star Proxima Centauri in the constellation Centaurus. It can also be referred to as Proxima b, or Alpha Centauri Cb. The host star is the closest star to th ...

, a planet of Proxima Centauri. 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. Although the signal was detected by

Parkes Radio Telescope Parkes Observatory is a radio astronomy observatory, located north of the town of Parkes, New South Wales, Australia. It hosts Murriyang, the 64 m CSIRO Parkes Radio Telescope also known as "The Dish", along with two smaller radio telescopes. T ...

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 A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...

(approximately 1/4 of a degree, half the angular width of Earth's moon) in

angular diameter The angular diameter, angular size, apparent diameter, or apparent size is an angular separation (in units of angle) describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the ''visual an ...

, containing Proxima Centauri, so the signal could have originated elsewhere in the Alpha Centauri system. The signal had a frequency of 982.002 MHz. The radio signal was detected during 30 hours of observations conducted by Breakthrough Listen through the

Parkes Observatory Parkes Observatory is a radio astronomy observatory, located north of the town of Parkes, New South Wales, Australia. It hosts Murriyang, the 64 m CSIRO Parkes Radio Telescope also known as "The Dish", along with two smaller radio telescopes. T ...

in Australia in April and May 2019. 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 Technosignature or technomarker is any measurable property or effect that provides scientific evidence of past or List of emerging technologies, present technology. Technosignatures are analogous to biosignatures, which signal the presence of life ...

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 dwarf A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...

s are

uninhabitable Inhabit means to live in, reside in, occupy or populate some place – a so-called habitat. Inhabit may also refer to: * ''Inhabit'' (album), an album by Living Sacrifice * Inhabited (band), a rock group See also * Circumstellar habitable zon ...

for humans and other currently known organisms. 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 In physical cosmology, the Copernican principle states that humans are not privileged observers of the universe, that observations from the Earth are representative of observations from the average position in the universe. Named for Copernican ...

made BLC1 very unlikely to be a technological radio signal from the Alpha Centauri System. On 25 October 2021, researchers published two studies concluding that the signal is unlikely to be a technosignature due to its similarity to previously detected terrestrial interference.

References

External links

* {{Portal bar, Astronomy, Stars, Outer space Unsolved problems in astronomy Proxima Centauri Search for extraterrestrial intelligence 2019 in Australia 2020 in science