NASA discovery may confirm signs of life in outer space

Earth occupies what planetary scientists sometimes call the “Goldilocks Zone.” Its distance from the sun means it is neither too hot, nor too cold to support liquid water – a key ingredient for life. Astronomers are perpetually on the lookout for planets that, like Earth, are ‘just right’ in this regard.

Last week, NASA announced it had discovered a system of seven new planets, three of which are firmly believed to be habitable. The discovery sets a new record for the greatest number of habitable-zone planets found around a single star outside our solar system.

This discovery of a “particularly unusual and exciting” planetary system is remarkable, said Stanimir Metchev, Western astrophysics professor and a Canada Research Chair in Extrasolar Planets.

“It’s exciting because all the planets are about the size of the Earth. When we are looking for other planetary systems, we’re trying to find the ones that might most resemble the Earth and, in this case, in size, these are all comparable – and at least two of them, maybe even more, are in the habitable zone,” Metchev noted.

The discovery may prove a significant piece in the puzzle of finding habitable environments in outer space. The question of ‘are we alone’ is “a top priority,” according to NASA, and finding this many planets in the habitable zone is a great step forward in answering this query.

Located roughly 40 light-years (235 trillion miles) from Earth, the system of planets – called the TRAPPIST-1 system – is relatively close to us. Last May, NASA researchers announced they had discovered three planets in the system. Assisted by several ground-based telescopes, including the European Southern Observatory’s Very Large Telescope, NASA’s Spitzer Space Telescope recently confirmed the existence of two of these planets and discovered five additional ones, increasing the number of known planets in the system to seven.

This artist's concept shows what each of the TRAPPIST-1 planets may look like, based on available data about their sizes, masses and orbital distances.

Courtesy of NASA/JPL-CaltechThis artist’s concept shows what each of the TRAPPIST-1 planets may look like, based on available data about their sizes, masses and orbital distances.

“All of a sudden, this system has been propelled to the forefront of being really the best candidate we have for studying habitable planetary systems. And the next thing we want to do is study the atmospheres of these orbiting planets,” Metchev said.

Looking at the atmospheres of the seven planets – called exoplanets because they are located outside of our solar system – is key to identifying potential for signs of life, he added.

“The way this can be done is in the mid-infrared regions of the spectrum with NASA, the Canada Space Agency and the European Space Agency’s next space telescope – called the James Webb Space Telescope, which will be launching in a year and a half.”

The James Webb Space Telescope, scheduled to launch in October 2018, will provide unprecedented resolution and sensitivity, giving planetary scientists the most advanced tool to date to study a planet’s atmosphere, looking for things like bio-signature gasses and the presence of life, should it exist, Metchev explained. Using this telescope, he speculates it would not take long to confirm signs of life.

“We’re not talking years of observations – it would probably be about a week or two, with the most powerful telescope we will ever have. Finding life, that would be fantastic; that would be the answer to millennia of philosophic pondering,” he said.

If we were to see signs of life on any of these seven newly-discovered planets, it would likely be signs of microbial life, Metchev added. We would need to detect things like oxygen and methane. When these two gasses exist together, it means they’re probably being generated at the same time on the planet we’re observing and that, as well as the presence of liquid water, would be an indication life currently exists.

“We know how hot and how bright the (TRAPPIST-1) host star is, and you have to be a certain distance from the star to have a surface temperature that is cool enough to have water in liquid form, or it’s warm enough for the water not to be frozen. If we just look at what the (planetary) temperature is, and the swath, there will be a region where the temperature will be just right for liquid water,” he continued.

“My team is now looking at this planetary system and trying to characterize the star. The star itself is cool enough that it has clouds, which is a very bizarre thing, and the better we know the star, the better we will be to plan observations with the James Webb telescope.”

The peculiarity about this system is all of the planets face the star they orbit with the same face, Metchev added. They are close enough to the star that their tidal forces are such the star always pulls the planet on the same side. It resembles our Earth/moon system, he explained, because we only ever see the one side of the moon.

“These planets all face the star with one side. That actually is a bit of a twist in the sort of habitability argument because the temperature distribution around the planet would not be constant. There would be a hot side and a cold side. But because of this, you could actually imagine a situation where even the hottest of the planets have, on their night side, a cool enough spot to have liquid water, and the coldest planets – the ones farthest out in this case –may on the day side, have a spot that’s warm enough to have liquid water. The unusual thing this produces is it may actually extend the habitable zone to encompass perhaps all of the planets. This makes the system particularly unusual and exciting,” he said.