Exotic SETI: Offbeat Ways to Look for Aliens

For decades scientists have been conducting SETI, the Search for Extraterrestrial Intelligence. Almost all efforts have gone into detecting radio signals. Despite one promising radio signal detection that remains unexplained (the famous Wow signal detected in 1977), there has been no undisputed success. Some scientists are now considering other ways to detect intelligent life on other planets.



Here are some of the unexpected ways that we might detect the hand of an extraterrestrial civilization.

Looking for Dyson Spheres and Similar Structures

The physicist Freeman Dyson has proposed that a highly advanced extraterrestrial civilization might aim to capture all or most of the solar energy coming from the star around which its planet revolves. The civilization could do this by building a sphere of solar energy collectors around the star. Such a sphere is called a Dyson Sphere. If such a sphere were built, the heat from it would give off lots of infrared radiation which scientists might be able to detect. Scientists such as Richard Carrigan have looked for sunlike stars with excess infrared radiation that might be the result of a Dyson Sphere. While some interesting candidates have been collected, nothing conclusive has been detected.

Looking for Artificial Planets

Let us imagine an extraterrestrial civilization many thousands of years more advanced than ours, or possibly millions of years more advanced than ours. Such a civilization might have the ability to move, break up and reorganize planets or moons within its solar system. The civilization might be able to do tasks such as (1) breaking up a gas giant and making it into smaller planets, which might be moved to a location closer to the local sun; (2) moving moons from a gas giant far away from the sun, to positions closer to the sun; (3) combining asteroids together to make a new artificial planet. Such activities might be possible to any alien civilization armed with an army of super-proficient robots.

NASA's Kepler Space Telescope has been very successful in detecting hundreds of extrasolar planets through a technique called the transit method, which tracks how the light of a star dims at periodic intervals when a planet passes between the star and an observer on Earth. Conceivably analysis of the Kepler data (or the data of its successor mission) might reveal indications of an artificial planet.

In fact, one could argue that what we have already discovered is a bit suspicious. The strangest finding regarding extrasolar planets is an unusually high number of “hot Jupiters” – Jupiter-sized planets that are very close to the stars they orbit (much closer than the orbit of Mercury). Could some of these be artificial planets – perhaps giant solar power collectors?

Imagine if an extraterrestrial civilization wanted to let other civilizations on other planets know that it existed. Besides sending out radio signals, the civilization could create a few artificial planets and position them in a way that indicated an artificial origin. One way to do that would be to make the relative distance of the planets from their sun follow an artificial pattern, such as 2, 3, 5, 7, 11, 13, and 17, the first seven prime numbers. Of course, it would be fantastically expensive to create such an arrangement, but once it was created, it would serve its purpose for billions of years. Any advanced civilization within 1000 light years (armed with its own version of the Kepler Space Telescope) might be able to detect the pattern, and know that intelligent life had existed on this planet.

It is conceivable that we might one day find evidence of extraterrestrial life by finding a planet pattern created by some alien civilization eager to broadcast its existence to its galactic neighbors.

Sniffing for Signs of Alien Life

One of the most powerful astronomical techniques is spectroscopy, which allows astronomers to detect elements in distant stars or planets. Spectroscopy involves passing the light from a distant light source through a prism. The prism breaks up the light into a series of colored bands. By analyzing those bands, scientists can tell what elements are in a distant star or planet.

We may soon be able to detect life on distant planets by using spectroscopy to analyze the light from planets detected through the Kepler Space Telescope. If we detect large amounts of oxygen in the planet's atmosphere, this would be an indication of abundant plant life. Most of the oxygen on our planet was produced by plants.

We might also be able to detect signs of intelligent life through such a technique. If we detected signs of chlorofluorocarbons (CFCS), this would be a telltale sign of extraterrestrial intelligence, as no natural process produces these molecules (produced on Earth through industrial processes).

Alien Gamma Ray Signals

An advanced civilization trying to get the attention of everyone in the galaxy could create a beacon using gamma rays, the most intense form of electromagnetic radiation. Astronomers have detected various gamma ray bursts from far away in space, most lasting less than a few minutes. Many of these are unexplained. It is easy to imagine us one day detecting a gamma ray burst with a deliberately encoded message, or with a deliberately artificial pattern.

Neutron Stars as Artificial Beacons

When the first neutron star or pulsar was detected, it was named LGM-1, with the LGM standing for Little Green Men. The pulsar made such an unusual radio source that astronomers initially wondered whether it was a radio beacon produced by an alien civilization. Today most astronomers think pulsars are purely natural phenomena, although Paul A. LaViolette has written a book arguing that some pulsars are artificial radio beacons. In any case, it is easy to imagine a superadvanced extraterrestrial civilization having the ability to manipulate a pulsar to use it as a signal transmitter. Such a technique might be worthwhile because of the great attention that pulsars attract (as they are a rare and interesting astronomical phenomena). Further analysis of the signals from neutron stars might one day turn up a telltale sign of an extraterrestrial intelligence.

The Search for Planets Like Earth

Scientists are busy looking for other planets like our planet. So far they have discovered some 889 planets. In addition, there are some 2712 “candidate planets.” These are cases where we have some data indicating that a planet probably exists at a particular place, but the data is not quite strong enough for scientists to conclude that the planet definitely exists.

Most of these planets have been discovered by the Kepler Space Telescope, which unfortunately has recently suffered a mechanical glitch which has put it out of service for the time being. But scientists will be busy for years analyzing the huge amount of data that Kepler has already collected. Even if the Kepler Space Telescope takes no more observations, it will be regarded as one of the greatest success stories in scientific history.

The Kepler Space Telescope mainly uses a technique called the transit technique. This technique is so simple that you could illustrate it to someone by using a light bulb and a rubber ball. Take the lampshade off a lamp, and tell someone the light bulb represents a distant star. Then revolve the rubber ball around the light bulb. Then ask the person, “How does your observation of the light bulb change when the ball passes in front of the light bulb?” The answer is that the observer sees less light from the bulb when the ball passes in front of it. The same thing happens (on a much different scale) to a telescope looking at a distant star when a planet passes in front of the star – for a short time a little less light is observed from the star. By taking repeated observations of a distant star over several years, and carefully analyzing dips in light from the star which occur at periodic intervals, scientists can detect planets around other stars. By exactly how much the light from the star dips, scientists can estimate the mass of these extrasolar planets.

What astronomers are most hoping to find are potentially habitable planets – planets that could support the existence of intelligent life. To be potentially habitable, a planet must not be many times smaller than our planet or many times larger than our planet. If a planet is too small, it won't have enough gravity to hold an atmosphere. If the planet is too many times larger than Earth, it would presumably be a planet similar to the gas giants in our solar system (Neptune, Uranus, Saturn and Jupiter), which don't even have solid surfaces. To be potentially habitable, a planet must also be in a zone that is neither too close to the star which it revolves around, nor too far away from the star. This zone where planets are not too hot and not too cold has been called the Goldilocks Zone (after the famous story for children in which a little girl rejects one bowl of porridge because it's too hot, another because it's too cold, and finally picks a third bowl of porridge which is just the right temperature).

The image below shows the current state of the search for habitable planets. So far astronomers have found 10 potentially habitable planets. Their relative sizes are shown below. All of these planets are in the Goldilocks Zones of the stars they resolve around.

Source: http://phl.upr.edu/projects/habitable-exoplanets-catalog

The decimal number under each planet is an estimate of how similar to Earth the planets are. The closest matches (with a similarity index of .82) could well be very similar to Earth. We will apparently have to wait until 2017 for the next great breakthrough in finding potentially habitable planets. In that year NASA will launch the Transiting Exoplanet Survey Satellite (TESS). It will have capabilities much greater than that of the Kepler Space Telescope. Some predict that this satellite will be able to discover between 1000 and 10000 planets.