SHGb02+14a is an astronomical radio source and a candidate in the Search for Extra-Terrestrial Intelligence (SETI), discovered in March 2003 by SETI@home and announced in New Scientist on September 1, 2004.
The source was observed three times (for a total of about one minute) at a frequency of about 1420 MHz, one of the frequencies in the waterhole region, which is theorized to be a good candidate for frequencies used by extraterrestrial intelligence to broadcast contact signals.
There are a number of puzzling features of this candidate, which have led to a large amount of skepticism. The source is located between the constellations Pisces and Aries, a direction in which no stars are observed within 1000 light years from Earth. It is also a very weak signal. The frequency of the signal has a rapid drift, changing by between 8 and 37 hertz per second. If the cause is Doppler shift, it would indicate emission from a planet rotating nearly 40 times faster on its axis than the Earth. Each time the signal was detected, it was again at about 1420 MHz, the original frequency before any drift.
There are a number of potential explanations for this signal. SETI@home has denied media reports of a likely extraterrestrial intelligence signal. It could be an artifact of random chance, cosmic noise or even a glitch in the technology.
The region is unusually devoid of any nearby stars. The closest star systems in the approximate region of the signal include the binary star G 73-11A and B, which are 106.1 light-years from the Sun, although the unrelated star G 73-10 is only 108.7 light-years away, less than three light-years from G 73-11A and B. All of these stars are red dwarfs much less massive than the Sun. The much nearer star, L 1159-16, which is one of the nearest 40 stars to the Sun, is near the signal's position, but its proximity is likely coincidental.
It is possible though highly unlikely that the reason for lack of stars in this region could be a Dyson sphere: this might be indirectly detected by looking for neutrino anomalies. Unfortunately unless a breakthrough is made in detecting them the noise level would be too high. Another possibility is to look for a near stellar mass black hole like object in the area as this might also be evidence of a Type II civilization who is using it as a gravitational lens to extend the range on their transmitter to message multiple systems with less power. 
References and notes
- Reich, Euginie (2004-09-01). "Mysterious signals from light years away". New Scientist. Retrieved 2006-06-12.
- Whitehouse, David (2004-09-02). "Astronomers deny ET signal report". BBC News. Retrieved 2006-06-12.
- Alexander, Amir (2004-09-02). "SETI@home Leaders Deny Reports of Likely Extraterrestrial Signal". The Planetary Society. Archived from the original on 2011-07-26. Retrieved 2006-06-12.
- Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
- "SETI on the Side: Seeking Dyson Spheres with Gaia". aasnova.org. Retrieved May 28, 2019.