NASA astronomers adopted a two-step process for detecting exoplanets using data gained by the Kepler Space Telescope and 11 other currently operating space telescopes. A new generation of space telescopes along with Earth based telescopes promise to provide even more data about exoplanets and their atmospheres. The world’s largest optical telescope is scheduled to begin construction this year on the summit of the Mauna Kea volcano at the Big Island of Hawaii – an hour’s drive from where this article is being written. The new 30 meter telescope is designed to examine exoplanets and their atmospheres for tell tale signs of life. The detection of large amounts of oxygen, for example, would be confirmation for the existence of extraterrestrial life.When an exoplanet is first detected as it either passes in front of (the transit method) or near enough to its sun to cause detectable wobble (the Doppler effect), it becomes a “candidate” until further data confirms its existence. Currently, there are more than 2500 exoplanet candidates. The length of time need to confirm exoplanets depends on the period of an exoplanet’s rotation around its parent star. As the exoplanet makes its second or subsequent passage in front of or near its sun, astronomers gain the additional data to learn whether or not a candidate exoplanet has been confirmed. So far, only two years of a four year data pool from the Kepler Space Telescope has been analyzed. As more data becomes available, additional exoplanet candidates are likely to be confirmed. Out of the 768 exoplanets just confirmed, 106 are less than 1.25 times Earth’s diameter. Previously, the data from Kepler and other telescopes had only confirmed 20 earth sized worlds. The four newly confirmed exoplanets orbiting in the habitable zones of their suns were roughly twice the diameter of Earth. This almost doubled the total of exoplanets confirmed in habitable zones from five to nine. What the NASA astronomers didn’t consider, however, was a new way of defining what constitutes a habitable zone for extraterrestrial life.
In January this year, Scientists at the University of Aberdeen and University of St Andrews, Scotland, released a paper titled “Circumstellar habitable zones for deep terrestrial biospheres,” in the journal, Planetary and Space Science. In the paper they redefined the “Goldilocks Zone”, the optimal zone for life to exist on planets. They have found that life can flourish beneath a planet’s surface where liquid water can be found at varying depths. This is how the abstract described this new way of locating extraterrestrial life:
We introduce a new term, subsurface-habitability zone (SSHZ) to denote the range of distances from a star within which rocky planets are habitable at any depth below their surfaces up to a stipulated maximum, and show how SSHZs can be estimated from a model relating temperature, depth and orbital distance. We present results for Earth-like, Mars-like and selected extrasolar terrestrial planets, and conclude that SSHZs are several times wider and include many more planets than conventional surface-based habitable zones.Using computer simulations, the scientists found that if one goes to a depth of 5km below the surface, then the habitable zone in space increases by a factor of three. If one goes to 10km below the surface, then the habitable zone extends by a factor of 14 which would extend the habitable zone beyond Saturn. Thus several of the moons of Jupiter and Saturn, could have life thriving in habitats kilometers beneath their surfaces.
Using the idea of subsurface-habitability zone, many more than only four of the 768 newly confirmed exoplanets could be suitable hosts for extraterrestrial life. As astronomers continue to develop new techniques for confirming the existence of exoplanets, a new understanding for what constitutes a habitable zone is needed. Liquid water can exist either on or beneath the surface of an exoplanet, thereby making it possible for extraterrestrial life to flourish on many more exoplanets than previously thought possible.In previous announcements of the Kepler Mission data, astronomers confidently predicted that it was only a matter of time before an exoplanet in the habitable zone of its sun would be found to host extraterrestrial life. New techniques for confirming exoplanets and new ways of defining a habitability zone make it even more inevitable that extraterrestrial life will eventually be detected on exoplanets using advanced space telescopes.
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