Space researchers now say we shouldn't rule out strange, distant worlds in our search for alien life.
Since the discovery of the first exoplanet in 1992, astronomers have been excited about the prospect of finding an alien world in its parent star’s “Goldilocks Zone” where life as we know it could be possible.
But for every earth-like planet we have detected, hundreds more with radically different properties have been discovered.
However, some researchers are now saying we shouldn’t rule out these strange worlds out of hand. Some of these unfamiliar-looking environments could yet be home to living creatures unlike any we have known.
51 Pegasi b, also called Bellepheron or Dimidium, was the first exoplanet discovered orbiting a star like our sun.
But the excitement of its 1995 discovery was dampened by the revelation that 51 Peg is a “hot Jupiter” – a giant gas planet orbiting closer to its parent star than Mercury does to ours.
Average temperatures on the planet have been estimated to be in the region of 1000°C
Nevertheless, in 2017 a team of astronomers led by Jayne Birkby detected the tell-tale signs of water in the massive planet’s ultra-dense atmosphere.
As 51 Peg is, like Mercury, totally locked to its star and doesn’t rotate it has a warm side and a cold side – with a narrow strip from pole to pole that’s somewhere between the two.
And while Mercury is very unlikely to be inhabited today, it’s not impossible that it might have been in the distant past. “We’ve been too hasty ruling out planets like Mercury as not habitable” says Alexis Rodriguez from the Planetary Science Institute in Arizona
If extreme conditions like the ones we might find on 51 Peg might seem like a long shot for life, there are other weird and wonderful worlds where life might find a way.
A lot of focus is now being placed on how long a stable environment can be sustained on a world.
Planets orbiting two suns for example, like Tatooine in the Star Wars films, could provide unusually stable habitats for a long-lived civilisation. “They are stable for a very long time,” Othon Winter at Brazil’s São Paulo State University told New Scientist – “enough time for life to develop”.
It's estimated up to 85% of all stars could be in binary systems. Over 50% of Sun-like stars are in binaries, and indeed it’s now thought that our Solar System until (in cosmic terms) recently contained a second star.
The existence of a second Sun in our system could even explain how life stared on Earth in the first place. Harvard researcher Amir Siraj says that a star out on the fringes of the current Solar System could have shaped the Earth we know today, adding: “Objects in the outer Oort Cloud may have played important roles in Earth’s history, such as possibly delivering water to Earth and causing the extinction of the dinosaurs."
But even systems with orbiting a long-dead star might be home to some form of life. Thea Kozakis at New York’s Cornell University says that white dwarf stars, stars that were once like the Sun but have now exhausted their nuclear fuel, could provide a stable environment for life to evolve – and maybe even to thrive for billions of years.
She says stable conditions could exist on planets orbiting a white dwarf for over eight billion years. Enough time for a civilisation to grow, expand, and develop technology that enabled them to live in the dim light of a dying star.
SETI’s John Gertz says it might be worth focusing on white dwarf stars in the ope of spotting ancient super-civilisations far in advance of our own.
“I wanted to look at it from ET’s point of view,” he says, saying that moving an entire planetary population to a new star system is probably impossible but huge stellar engineering projects designed to maintain the habitability of ancient planets might be detectable by the next generation of telescopes: “We need to shift our entire paradigm of looking at stars for signs of life.”