The Search for Extraterrestrial Intelligence has has it tough for a long time. Recall the UFO period and the rampant speculation.
The Ohio State SETI program gained fame on August 15, 1977, when Jerry Ehman, a project volunteer, witnessed a startlingly strong signal received by the telescope. He quickly circled the indication on a printout and scribbled the exclamation “Wow!” in the margin. Dubbed the Wow! signal, it is considered by some to be the best candidate for a radio signal from an artificial, extraterrestrial source ever discovered, but it has not been detected again in several additional searches.
The size and age of the universe incline us to believe that many technologically advanced civilizations must exist. However, this belief seems logically inconsistent with our lack of observational evidence to support it. Either (1) the initial assumption is incorrect and technologically advanced intelligent life is much rarer than we believe, or (2) our current observations are incomplete, and we simply have not detected them yet, or (3) our search methodologies are flawed and we are not searching for the correct indicators, or (4) it is the nature of intelligent life to destroy itself.
The universe is so vast that it makes perfect sense that other stars have planets in the viable zone and some of them have the resources for life to emerge. Planets outnumber stars suggesting may one in one hundred stars has a viable planet.
Double stars are less likely to have viable planets as the stars tend to self destruct in rather short order. When one star collapses it tends to then draw material from its neighbor leading to a supernova event trashing any nearby planet instantly.
Alpha Centauri is a triple star system. Its only 1.34 parsecs away so its easily seen. Alpha Centauri A has 1.1 times the mass and 1.519 times the luminosity of the Sun, while Alpha Centauri B is smaller and cooler, at 0.907 times the Sun’s mass and 0.445 times its luminosity. The pair orbit around a common center with an orbital period of 79.91 years. Currently, the distance between Proxima Centauri and Alpha Centauri AB is about 13,000 astronomical units (0.21 ly), equivalent to approximately 430 times the radius of Neptune’s orbit.
The sun is considered to be a class G star. The power is driven primary by the CNO fusion reaction which converts hydrogen to helium. About 7.6% of known stars are similar to the sun as class G. It is believed that the sun will be viable for a few more billion years before it becomes a red giant and trashes the inner solar system.
Class K stars are 0.45–0.8 suns and tend to be light orange to pale yellow orange. The power is driven primary by the CNO fusion reaction which converts hydrogen to helium. About 12.1% of known stars are similar to the sun as class K. Class K stars last substantially longer than class G stars due to the lower fusion temperatures.
Given that class G and K stars are longer lived it is suggestive that these are more likely to find viable planets with actual life present. It took the Earth a couple of billion years to discover photosynthesis. It took another couple of billion years to change the Earth adequately to support more complex organisms. It is obvious that planets vary so the timeline for evolution can vary substantially.
By nature planets are hard to see from a distance due to the glare of the star. Sending probes in various directions to a distance of 10 parsecs and returning would give a clearer understanding of the region. Eventually expanding the probes radius to 25 parsecs will encompassed a larger number of stars which can be investigated,
Radio signals are the primary area of research. It is speculated that signals near the hydrogen lines are more likely to be indefinable. The problem is that detailed analysis will require some sophisticated analysis that will motivate more work in signal analysis which attracts defense spending. SETI and defense both need better signal processing so both can help each other. Large planets like Jupiter generate cyclotron maser activity which drives the creation of bright auroras visible at a great distance.
Fourier analysis is all fine and dandy but it can be brutal to handle 1 million hours of observations. Mainframes are not presently powerful enough and microprocessors, while cheap, are not capable of advanced analysis. Existing spectrum analyzers are swept-tuned instruments and are unsuitable.
Work on SETI will depend on better signal processing so this is rich area of research. 1665 MHz was found to be hydroxide emission lines, 4830 MHz was found to be formaldehyde.