NASA announcement reveals seven Earth-like planets orbiting dwarf star

22 Feb 2017

An artist’s impression shows the view from the surface of one of the planets in the TRAPPIST-1 system. Image: ESO/M Kornmesser

In one of the biggest hauls to date, a team of astronomers has discovered seven Earth-like planets, six of which could sustain liquid water.

Following NASA’s announcement that it was to hold a press conference regarding a major discovery beyond our solar system, speculation had been mounting.

Before today, all we had to go on was the fact that it was related to the search for planets that orbit other stars, otherwise known as exoplanets.

Potential for liquid water

The mystery has been unveiled as a monumental discovery of seven planets similar in size to our own.

Of that number, it is estimated that six of them them could have liquid water on their surfaces, with atmospheric temperatures similar to our planet’s.

As revealed yesterday by, one of the key people at today’s announcement was Belgian astronomer Michael Gillon, who has spent years studying exoplanets using TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope), a 60cm telescope.

Using this powerful apparatus, Gillon and his team were able to locate the haul of exoplanets that orbit an ultra-cool dwarf star, now dubbed TRAPPIST-1.

The discovery was made after noting dips in the star’s light output, caused by each of the seven planets passing in front of it. These events are referred to as transits.

This allowed the astronomers to gather information about their sizes, compositions and orbits. They found that at least six planets are comparable in both size and temperature to Earth.

The Very Large Telescope used by the ESO in the hunt for exoplanets. Image: Iztok Bončina/ESO

First of its kind

Described as an “amazing” planetary system by Gillon, TRAPPIST-1 is tiny in comparison to our own sun, with just 8pc of its mass, and is only slightly bigger than Jupiter.

While dwarf star systems like this have been considered potential hotspots for finding ‘Earth 2.0s’ and harbouring extraterrestrial life, TRAPPIST-1 is the first of its kind to be discovered.

“The energy output from dwarf stars like TRAPPIST-1 is much weaker than that of our sun,” said Amaury Triad, co-author of the research paper.

“Planets would need to be in far closer orbits than we see in the solar system if there is to be surface water. Fortunately, it seems that this kind of compact configuration is just what we see around TRAPPIST-1.”

Three planets in Goldilocks zone

With all of the seven planets of a similar size to either our own planet or Venus, perhaps the most exciting aspect for astrobiologists is the fact that liquid water could exist on nearly all of them.

However, climate models suggest that the three innermost planets in the system might be too hot to support liquid water and the outermost might be too cold. The three middle planets – dubbed TRAPPIST-1e, f and g – fall within the ‘Goldilocks zone’, described as a “holy grail” for astronomers.

With this new information, TRAPPIST-1 will receive considerable attention using some of the world’s most powerful space and Earth-based telescopes, such as the European Southern Observatory’s Extremely Large Telescope and the future James Webb Space Telescope.

“With the upcoming generation of telescopes … we will soon be able to search for water and perhaps even evidence of life on these worlds,” said team member Emmanuël Jehin.

The team’s findings have been published in the scientific journal Nature.

Colm Gorey was a senior journalist with Silicon Republic