September 16, 2021
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first_imgThe universe just got a whole lot smaller. This week scientists at the European Southern Observatory confirmed the discovery of an Earth-like exoplanet orbiting in the habitable zone of Proxima Centauri and published their findings in Nature.This is huge. Massive. Proxima Centauri is the closest star to Earth (besides the Sun, obviously), and given that we’ve already found hundreds of exoplanets, this could mean that the universe really is littered with life. After all, just about every star we turn to seems to have a few planets, often with at least one in the habitable zone — a region around a star that could be just the right temperature to allow for liquid water on the surface.For now, the planet has been dubbed “Proxima b.” According to the European Southern Observatory, it’s just 1.3 times the mass of Earth. It’s still much too early to tell what its atmosphere is comprised of, or what surface conditions are like, but, for now it looks promising.Proxima b orbits a mere 4.3 million miles from its star — whereas we sit about 93 million miles the Sun. Even so, Proxima Centauri is a red dwarf, one of the coldest types of stars, so 4.3 million miles is just fine.What makes this discovery even juicier is that red dwarfs are by far the most common type of star in the universe. They’re also some of the longest lived. Our own sun, a yellow dwarf, will burn out in another five billion years, but Proxima Centauri will keep shining for trillions of years. This gives life a huge amount of time to find the right conditions and evolve. Plus, looking at our own planet, life seems to be pretty versatile. Earth first showed signs of life a few hundred million years after the crust first cooled — stunningly fast on a cosmic scale. Combined with the fact that we’ve managed to live through half a dozen major mass extinctions, and the odds of life evolving quickly and early on any given planet start to look pretty good.But, there are a few caveats here. Earth, so far as we know, is still unique. To date, no signs of life have been found on any of the other exoplanets we’ve discovered. Though the building blocks for life — amino acids, hydrocarbons, and water — seem to be extremely common throughout our solar system, and probably the rest of the universe, we still don’t know enough to say for sure.It may be that Earth truly is special. While Proxima b looks really good on paper, it’s also been pelted with X-rays from its parent star — more than enough to blast away just about any atmosphere. If we ever visit the planet we might find little more than a sun-scorched wasteland.Even so, it’s a perfect target for our first interstellar missions. Starshot, a proposed mission that would launch countless tiny spaceships on beams of light, could cross the 4.2 lightyears that lie between Earth and Proxima b in as few as 20 years. A human-piloted mission would be decades, perhaps even a century off, however.For now, Proxima b represents one of the most important discoveries we’ve ever made. Finding another Earth-like planet, on top of the hundreds of others we’ve seen over the past few years, could mean that our universe really is teeming with life. At the same time, however, it begs the question — if conditions for life are this common, and it certainly seems like they are, then why haven’t we found any aliens?One thought experiment, known as the Drake equation, tries to estimate the number of other civilizations that might exist in our galaxy. It takes statistics like how many stars have planets and the fraction of those that develop intelligent life and spits out a number of civilizations we could expect to find. The Drake equation isn’t scientifically sound, as it requires half a dozen assumptions which can change the results wildly, but right now it seems that we keep finding planets that could, in fact, support life. Meaning that the potential ranges of numbers the equation will produce is getting smaller and smaller. That, of course, makes life more and more likely. If that’s the case, then we would expect to have already found some aliens.The famous counter to the Drake equation is the Fermi paradox. Even assuming some fairly conservative figures, we should see countless other alien civilizations streaking through the stars. What could that mean? The late astrophysicist Carl Sagan wondered if advanced civilizations like ours were prone to self-destruction. The Cold War, for example, could have very easily wiped out just about all life on Earth — and nuclear proliferation and global political instability may still end us all.While each new Earth-like planet is an exciting discovery, it’s also a sobering one and means that life might be more fragile than we thought. We may well yet be alone in our universe.last_img