Pasadena (USA) – A recent review of recent data from Earth-based and space telescopes shows that while the previously estimated number of potentially Earth-like and life-friendly planets in our Milky Way galaxy remains high, it still needs to be downsized.
Of the 3,700 so far discovered and confirmed exoplanets (3,000 other so-called planetary candidates are currently waiting to be confirmed by further observations) were detected alone by the NASA Space Telescope “Kepler” 2,600. So far, planetary scientists have estimated that 20-50 percent of the stars in our night sky are orbited by planet-sized planets within habitable zones. “Kepler” alone – so suspected it was the estimates of NASA scientists in mid-June – discovered about 30 Earth-sized exoplanets that orbit their star within the so-called habitable zone, ie in that distance region within which a planet must circle its star,
However, data from the European Space Telescope Gaia now show that the actual number of such potentially life-friendly planets is actually around 30, only between 2 and 12, says Eric Mamajek, chief scientist at NASA’s Exoplanet Exploration Program. The reason: The Gaia data show that some of the stars observed by Kepler are brighter and larger than previously thought. Thus, the planets discovered around these stars are larger and hotter than previously thought – some too hot for life as we know it.
The most important factor is how well we know the central planets, “explains Mamajek. “Because of their brightness, size, and heat, the conditions depend on the planet there.”
The new findings show that more data is needed to better understand the relationship between the size of the planets and the composition of the celestial bodies: “We need to understand more precisely how large a planet can be to still be rocky (earthy) “, adds astrophysicist Jessie Dotson of NASA’s Ames Research Center, who is a project scientist accompanying the expanded Kepler mission” K2 “.
Although the revaluation initially sounds disappointing as far as the prospects for extraterrestrial life are concerned, the basic message of all the observations of the last 20 years does not fundamentally change: given the unimaginable number of stars, planets within the habitable zone are still numerous and probably more so Usually as the exception.
In addition to the classic Earth-like planets, there are also other worlds on which life, even as we know it from the earth, can exist despite initially seemingly adverse conditions. Even in our own solar system, numerous ice moons around the gas giants Jupiter and Saturn have oceans of liquid water under their ice sheets. In addition, scientists are also speculating about other forms of life that use water instead of water, other liquids such as the liquid cycle (rain, snow, seas, lakes and rivers) on the Saturn moon Titan forming hydrocarbons methane and ethane.