Scientists are now finding evidence that there are a lot of apparently habitable planets out there, in a temperate zone in relation to their suns, where water is likely to form.
So why in the world (pun intended) aren’t we hearing or seeing signs of alien life when we point our radio telescopes at other star systems? Our ability to search for evidence of life elsewhere has developed to the point where the lack of any contact has to be considered in any scientific theory about how life develops — and scientists are, in fact, doing just that.
The new theories posit that the world — our world — in fact played a key role. They envision a “Gaian Bottleneck”: a kind of choke point that most alien life doesn’t survive. While early, microbial life forms may have developed on those wet, rocky planets scientists are identifying just about everywhere, more complex life forms require planets with weather systems and atmospheric that are relatively stable. The Gaian Bottleneck posits that such stability is lacking on many planets, and that changes in temperature or atmosphere killed off the alien life when it was in its fragile, early stages and unable to defend itself through evolution. Thus, both Venus and Mars may have had early life forms, but the developmental arc of those planets — toward a high-pressure hot house on Venus, and a frigid, barren desert on Mars — killed them off.
Earth, though, somehow threaded the needle. So, we’re special.
Of course, Earth’s example means some planets make it past any Gaian Bottleneck, so there may be advanced life out there — just not as much as you might think.
Science continues to achieve amazing advances in our ability to detect, measure, and analyze planets orbiting stars far outside our solar system.
So far, scientists have discovered and confirmed the existence of more than 800 planets. Most of the planets, however, are huge gas giants, like Jupiter or Saturn in our solar system. The latest advance in detection capabilities came this week, when scientists announced that they have detected the lightest planet to orbit a Sun-like star — and the star just happens to be Alpha Centauri, a weird, triple-star system that is the Sun’s nearest galactic neighbor.
Alpha Centauri, for those who fell asleep during astronomy class, is a mere 4.3 light years away. Of course, one light year is 6 trillion (6,000,000,000,000) miles away, but who’s counting? The planet scientists have detected is about the mass of our good Earth.
Before you start worrying that little green men might appear on your doorstep tonight, take a deep breath: the Earth-sized planet is closer to Alpha Centauri B than Mercury is to the Sun, so it’s probably not conducive to life. Still, the discovery is remarkable. In the not too distant future, scientists will use this detection technology to find a planet about the size and mass of Earth, orbiting a star a lot like Sol, at a distance that would suggest that it is likely to be temperate. What will that mean? My guess is that we will train every radio telescope and sensory device we have in the direction of that planet, listen as hard as we can, and hope.
The Oort Cloud is an enormous, spherical cloud of icy objects that surrounds our solar system. The Cloud is awesomely distant from us — somewhere between 5,000 and 100,000 times farther away from the Sun than the Sun is distant from the Earth. The outer reaches of the Oort Cloud are thought to be trillions of miles from the Sun. The Oort Cloud also is the source of many of the comets that eventually are tugged by the Sun’s gravity and fall toward Sol, with their tails of ice and debris spread behind them, sailing on the solar wind.
Now astronomers wonder whether the Oort Cloud hides some massive new planet that is four times the mass of Jupiter. Some scientists suspect such a planet is there, because they believe it explains otherwise inexplicable gravitational issues observed in comets. Others are skeptical. They are waiting until data from a NASA sky survey initiative is released later this year, because such data should either confirm or refute the theory.
It’s hard to imagine that an object that is four times the size of Jupiter could be lurking undetected in the outer boundaries of our solar system — but then the Oort Cloud is largely unexplored, and very far away. If the existence of a massive new planet is confirmed, it will just show, again, how much we have to learn about our little corner of the universe.