NASA reveals “sister solar system” just 39 light years away

Planets that could support life are like buses – you wait for years, and suddenly a bunch come along at once. Who could forget Kepler-452b, or Proxima b? Well NASA has announced another seven potential candidates, all orbiting the same dim star 39 light-years away.

To get one thing clear early on: we currently have no way of travelling to what NASA is referring to as our “sister solar system”. Thirty-nine light years isn’t that much in the greater scheme of things, but with speeds matching Voyager 1, you’d be looking at around 17,000 years travel time. Don’t get me wrong – that’s much more accessible than Kepler-452b, but yeah: you’re still going to die on Earth.

With that predictable but sad news out of the way, why should you still care? Chiefly because, even if we can’t get there ourselves, there’s still an awful lot we can learn from here on Earth – and we’ll be able to learn even more when the James Webb telescope opens next year.

So here’s what we know now. You’re looking at seven exoplanets all orbiting a star called TRAPPIST-1 in the Aquarius constellation. TRAPPIST-1 is small and dim, and while that may sound pejorative, it’s pretty handy for us as it means that our telescopes aren’t dazzled as they would be by bigger and brighter stars. The researchers estimate that five of the seven exoplanets have masses similar to Earth and that at least six of them are rocky with surface temperatures in the 0 to 100°C zone – making liquid water, and therefore life as we understand it, possible. That’s exciting stuff, and goes some way to explaining why the study’s authors write that “The TRAPPIST-1 system is a compact analogue of the inner solar system.”

The word “compact” is key here. TRAPPIST-1, the star the seven exoplanets orbit, is just a touch bigger than Jupiter, and the planets surrounding it are only slightly further away than Jupiter’s moons in our own solar system. That means that the first six planets take between 1.5 and 13 days to orbit the star. (How long the seventh takes to orbit is unknown, having only been seen once to date.)

“Who cares how compact the system is?” you might ask. The reason it’s important is that it’s possible having the planets so close together could cause them to interfere with each other, possibly even causing some kind of tidal locking where a face of the planet always points towards the star. If that’s the case, that could do strange things to the planet’s temperature, making liquid water harder to maintain. There’s also the fact that some cooler smaller stars emit large amounts of radiation in flares. If that applies to TRAPPIST-1, the nearby planets’ surfaces could have been affected.

Nonetheless, there’s another big reason this is exciting, other than the obvious: finding seven potentially life-hosting planets in one go means that there’s likely plenty more where that came from. As astronomer Ignas A G Snellen writes in an accompanying piece on Nature: “In the past few years, evidence has been mounting that Earth-sized planets are abundant in the Galaxy, but Gillon and collaborators’ findings indicate that these planets are even more common than previously thought.

“Of course, the authors could have been lucky, but finding seven transiting Earth-sized planets in such a small sample suggests that the solar system with its four (sub-)Earth-sized planets might be nothing out of the ordinary.”

With the James Webb Space Telescope due to replace the 27-year-old Hubble Telescope next October, space discoveries are likely to come thick and fast over the next few years. Hopefully we’ll see a positive answer to the Fermi Paradox yet…

Image: NASA

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