CTA-102

The CTA 102 facility was discovered in the early 1960s by researchers at Caltech as a powerful radio source ^[2] . Over the years, a significant range of scientific tools was used to study it, including WMAP and GALEX ^[1] , ADU-1000 ^[3] . CTA 102 was also identified as a source of gamma radiation ^[4] .

In 1964, astronomer N. S. Kardashev published a paper that became the first Soviet contribution to the search for extraterrestrial intelligence ( SETI ). In it, he calculated the spectrum of a possible artificial radio source (transmitter of an extraterrestrial civilization), based on the optimal distribution of transmitter energy in order to ensure the maximum information transfer rate over the channel with noise. It turned out that such a spectrum is significantly different from the typical spectrum of natural radio sources. Having studied the observable data available at that time, Nikolay Kardashov singled out two objects with suitable spectra. These are STA-21 and STA-102, which, by the way, had very small angular dimensions, which also met the criterion of artificiality. To test the hypothesis of artificial origin, he proposed to investigate whether the flux of radio emission from these sources is not variable. The fact is that the radio sources known at that time did not have any variability ^[5] .

The verification of variability by G. B. Sholomitsky, a staff member of the P. Sternberg State Astronomical Institute , who was engaged in radio astronomical observations on the ADF-1000 - antennas of the Center for Long-Range Space Communications of the USSR in Yevpatoria ^[6] .

Observations were carried out at a frequency of 920 MHz for several months in 1964-1965. The flux of the sources STA-21 and STA-102 was measured in relation to the reference source ZS-48. All possible sources of error have been carefully investigated and taken into account. The radio source STA-21 showed no variability, and at the source STA-102 days a flow change with a period of 102 days was detected, which coincided with the number of the object itself ^[3] .

On the discovery of the periodicity of STA-102, a number of discussions took place at the P. Sternberg Institute, one of which was attended by TASS correspondent A. Midler, who was engaged in scientific journalism. The report of A. Midler about alleged signals from an alien civilization transmitted through TASS channels on Cosmonautics Day on April 12, 1965 caused a worldwide sensation ^[6] .

Soon, however, the work carried out by the Palomar Observatory proved that CTA-102 is a natural object - a quasar ^[2] .

The further fate of this discovery of the CTA-102 variability is interesting. Near observatories, the variability of quasi-stellar radio sources (quasars), including CTA-102, was investigated. The works did reveal a fundamental phenomenon — the variability of radio emission from quasars. However, the variability of CTA-102 itself was not revealed. However, in 1972, the variability of radio emission STA-102 was again noticed by the Canadian radio astronomer J. Hansted, and then confirmed by other researchers. In this regard, it was suggested that the temporal nature of the CTA-102 variability, that is, the alternation of periods of variability and stability, is temporary ^[6] .

• Blytsar
• Fast radio pulse
• Wow! Signal
• Radio signal SHGb02 + 14a
• PSR B1919 + 21