Unless you’ve been living under a rock for the past week, you might have heard about NASA’s latest discovery confirmation of a dwarf star with 7 Earth sized, potentially habitable worlds orbiting it.
NASA has described the finding as the most spectacular exoplanet discovery to date and the most promising sign of finding life outside our own solar system. The 7 planets that orbit the TRAPPIST-1 system are extremely close their star, closer even than Mercury is to the Sun. They are also extremely close together and they would appear massively in the sky if someone were looking up from the surface.
So you might wonder how they can be so close and yet still habitable, given that Mercury and Venus, the closest planets to our star, both ahve extreme environments that are unsuitable for holding liquid water and therefore possibly life. The answer lies in the fact that TRAPPIST-1 is a pretty dim star; not that it’s bad at math or anything; it’s just 2000 times dimmer than our Sun and a lot smaller. This should also mean that it gives off harmful less radiation that might otherwise reduce chances of life forming. At least 3, and perhaps all of the 7 discovered planets lie in the habitable zone of the star, where liquid water can form.
“The planets are all close to each other and very close to the star, which is very reminiscent of the moons around Jupiter. Still, the star is so small and cold that the seven planets are temperate, which means that they could have some liquid water – and maybe life, by extension – on the surface.” Michaël Gillon – University of Liège
Just because the planets lie in the habitable zone, there is no guarantee that water has formed on the surface, or that it ever did or would. For that to happen the planet needs an atmosphere and we can’t tell if that is the case yet. The planets might also be tidally locked, given that planets closer to a star often are. This means that one side of the planet would be stuck in perpetual darkness and one would be kept in the heat. The planets might also be very dim to human eyes, as scientists reckon that the majority of the light is radiated in the infrared wavelengths rather than visible wavelengths as it is here on Earth. The planets would be warmed by the Sun, but they wouldn’t get much brighter than our own sky just after sunset.
Years don’t take very long on the planets of Trappist, as the outermost planet takes just 20 of our days to complete an orbit of the star. This means that a year on the outermost Trappist planet takes just under 3 weeks. The inner planets go even quicker with the innermost planet having a year that takes just a day and a half.
“The planets tug and pull each other as they go orbiting around their star. What that does is it changes the timing of the transits a little bit, as the planets are tugging each other, so they (the transits) aren’t happening as regularly as you would expect without the tug” – Sean Carey – NASA’s Spitzer Science Center at Caltech in Pasadena, California.
So when do we leave?
The problem is that Trappist is 39 lightyears away from Earth. It is a relative hop, skip and a jump in galactic terms, but too far for any current technology to send intrepid explorers to pay a visit. We will continue to study the system in great depth for the next few years at least, especially with the James Webb Space Telescope (JWST) hopefully getting operational in 2018. Trappist will be one of the highest priority targets for JWST. By the early 2020’s, we should know far more about the chemical makeup of the planets, including a more educated answer to the question everybody wants to know; are they habitable?
With current and known technology, excluding EM Drives and hypothetical motors, the Breakthrough Starshot project is our best hope of sending something to Trappist. The Breakthrough Starshot project uses lasers to speed up tiny probes equipped with sails and monitoring equipment. Even still, and don’t get too disheartened by this, the Breakthrough Starshot project will take 200 years at maximum capacity of 20% of the speed of light to reach Trappist.
200 years is a blink of an eye in galactic terms, but not currently a nice number for people alive today. Our only real hope is that some genius can invent faster-than-light travel which is being explored by different organizations around the world. Time will tell if we can invent such a device, but for the meantime we will have to make do with increasing our knowledge of Trappist and its exoplanets, and discovering if any of them might be habitable.