A stylised view of the TRAPPIST-1 star system, an ultra-cool dwarf, has seven Earth-size planets orbiting it. Any of these planets could have liquid water on them. Picture: NASA

The announcement last week of the discovery of seven worlds, six of which are capable of holding liquid water, around a nearby star was greeted with excitement in astronomical communities.

That one dull-red star and its system of rocky worlds, three of which sit squarely in the ‘goldilocks zone’, just considerably upped the odds that there is life out there.

Now all we have to do is find it.

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It’s not an easy task, given the immense distances involved.

But we can get a glimpe as to the make up of different worlds by the ‘fingerprints’ their atmospheres leave on light that passes through them.

It remains an enormous task to separate light reflected from atmospheres from the background light of TRAPPIST-1 itself. But as the star is only 40 light years away, this remains a possibility.

The Hubble Space Telescope team has already been on the task.

WEATHER EYE

It announced in July it had conducted its first search for atmospheres around Earth-sized planets orbiting a distant star.

Even before it was known to hold seven planets, TRAPPIST-1 was the subject of its search.

Initial results confirm its planets are unlikely to have the “puffy, hydrogen-dominated” atmospheres of gaseous worlds.

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“The lack of a smothering hydrogen-helium envelope increases the chances for habitability on these planets,” said Nikole Lewis of the Space Telescope Science Institute. “If they had a significant hydrogen-helium envelope, there is no chance that either one of them could potentially support life because the dense atmosphere would act like a greenhouse.”

Hubble’s Wide Field Camera 3 caught TRAPPIST-1’s light in the near-infra-red. Being a red dwarf star, this is the spectrum in which it is strongest.

Spectroscopy — where light is broken up to reveal its component colours — was used to decode the potential chemical makeup of any atmospheres the light may have passed through.

The few clews Hubble has so far been able to discern appear to rule out gas giants like Jupiter because of apparently low concentrations of hydrogen and helium.

“These initial Hubble observations are a promising first step in learning more about these nearby worlds, whether they could be rocky like Earth, and whether they could sustain life,” acting associate administrator for NASA’s Science Mission Directorate Geoff Yoder said. “This is an exciting time for NASA and exoplanet research.”

A computer-rendered illustration of the James Web Space Telescope displaying its primary mirror, sun shield, solar panels and spacecraft bus. Picture: NASASource:Supplied

A CLOSER LOOK

The operators of Hubble’s replacement, the James Webb Telescope, are also planning to put that star and its seven rocky worlds — three of which are ideally positioned for life-forming conditions — at the top of its priority lists.

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The new tennis-court sized space telescope is due to be launched into space in October 2018. It is hoped to be fully functional by April 2019.

It will be ideally suited to identify the components in the atmospheres of TRAPPIST-1’s worlds.

“This is a tremendously exciting possibility for the JWST, and we most certainly will observe this system,” James Webb Program Director Eric Smith told Inverse.

“If it’s got liquid water, it’s got water in its atmosphere, it doesn’t have something super poisonous in its atmosphere, that’s a place that could support life, and that would be tremendously exciting.

“We won’t be able to detect that life with JWST, but I think that would be a tremendous discovery in and of itself to say, ‘that place could have life.’”

This handout artist’s impression released by the European Southern Observatory shows the view just above the surface of one of the planets in the TRAPPIST-1 system. Picture: ESOSource:AFP

RED DWARF’S GIANT POTENTIAL

TRAPPIST-1 is a red dwarf star that is at least 400 million years old. Being smaller and cooler than our own Sun, it is likely to have a considerably longer lifespan.

Two exoplanets were discovered in its orbit in late 2015 by the TRAnsiting Planets and PlanetesImals Small Telescope (TRAPPIST), a Belgian telescope at the European Space Agency’s Chile observatory.

Follow-up observations last year revealed the presence of five more worlds. Six are believed to be rocky and capable of holding liquid water. Three sit in the optimal ‘Goldilocks’ band where temperatures are neither too hot nor too cold for life as we know it. The seventh is believed to be an ice world.

Small red stars can regularly erupt with powerful X-ray and UV flares, bombarding their worlds — which sit in close orbits — with radiation.

So could life survive such conditions?

Researchers say worlds with atmospheres similar to our own would offer enough protection to life on their surface. Atmospheres would also enhance the habitable ‘twilight’ zone between the ‘hells’ of fire and ice likely a feature of planets tidal-locked with their red dwarf stars.

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