NASA have discovered a planet with the closest conditions to Earth we have ever seen. It’s been given the adorable name ‘452b’ and for all we know it could already sustain life…
By Phoebe Vowles-Webb
452b is described as “a pretty good, close cousin to the Earth” by NASA’s John Grunsfeld. It takes just a little longer to travel around its sun than Earth, having 20 days more in each year, and is around 60% bigger than our planet. Most importantly, the Kepler team at NASA believe it holds a circular orbit around its host star inside the ‘habitable zone’. This means that 452b has a consistent temperature just right for liquid water to pool on the planet’s surface, which in turn gives life the chance to grow. Essentially 452b is in the Goldilocks’s zone: the conditions are just right for life.
There is disagreement, however. The New Scientist implies that because 452b is receiving 10% more energy from its star than Earth does, the planet could be experiencing a severe (runaway) greenhouse effect, making it inhabitable. This would mean that, contrary to appearances, the planet is nowhere near the Goldilocks’s zone.
I spoke to Jon Jenkins, Kepler Data Analysis Lead, to find out whether the New Scientist was right…
Brace yourselves, it’s time for some maths. It’s true that for a planet with a mass such as Earth’s, just 1.1% more energy could produce a runaway greenhouse effect. But Jenkins estimates 452b to be 5 times the mass of Earth. If he’s right, 452b would need to receive 20% more energy from its star than Earth does to have a runaway greenhouse effect. As Kepler 452b only receives 10% more energy than Earth does from the Sun, such an effect is unlikely. The bottom line then? While a runaway greenhouse effect can’t be completely ruled out, it’s certainly possible that Kepler 452b is capable of sustaining life.
Further study is needed to confirm the conditions before we can resolve the debate. Jenkins argues that we do not understand enough about planets to know where the habitable zone ends. “Most astronomers adopt a broader definition for the habitable zone that allows for approximately 80% energy from the star before the planet exits the habitable zone”, he says. At the very least, further study of 452b will offer the chance to refine this complex definition. What remains undisputed is that the starlight 452b receives is similar to Earth’s, which means that at the very least there aren’t deadly levels of ultraviolet rays every sunny afternoon.
It’s when we compare Earth to the newly discovered planet that we can begin an interesting analysis. 452b has been in the habitable zone of its star for longer than the Earth’s age, which is clearly plenty of time for life to grow. However being within a habitable zone is no guarantee that a planet will be habitable. For example, Jenkins told me that “a planet as massive as 452b is likely to be able to retain a Hydrogen/Helium envelope”, meaning that the incredibly high density of its atmosphere could make the pressure on the planet’s surface too great for life. Having said this, high pressure atmospheres don’t have to stop life in its tracks; microbes and animals have survived for millions of years at the bottom of Earth’s seas in similar conditions.
During 452b’s 6 billion years in the habitable zone, it’s possible that life has developed and died out, or it could be flourishing as you read this. Though there are still a lot more conditions to verify before we can consider this to be the case. It is not even certain that 452b is rocky, but Jenkins confirms there is a 50-60% chance. It’s still possible Kepler 452b could be gaseous, like “some kind of warm mini-Neptune”.
Not only is this discovery of an earth-like planet encouraging, but Jenkins affirms “there should be many such planet/star combinations much closer to Earth that could be studied in much greater detail”. 452b is a bit too far away to easily study, being 1,400 light-years from Earth, so the prospect of other closer candidates for “Earth 2.0” is exciting and intriguing in equal measure.
There should be many such planet/star combinations much closer to Earth that could be studied in greater detail…
Even if there is no life on this planet, its discovery offers a chance to look into our own Earth’s future. 452b is so similar to our planet it could be an “older cousin”, representing a future stage in the Earth’s own changing climate. Because of this the study of exoplanets similar to Earth, however many light years away they may be, is valuable in that it can give us an insight into what our world may be like in the years to come.
A big thank you to Jon Jenkins, who kindly took the time to explain some of the finer details. Here’s to many more discoveries in the future.