Study gives new insights into TRAPPIST-1 exoplanets

Doug Carpenter
February 7, 2018

The results of their one-year-long study of the TRAPPIST-1 system are revealed in the form of four separate papers.

The data regarding these planets were found using NASA's Spitzer and Kepler telescopes with the findings being published in the Astronomy and Astrophysics journal. Research teams gleaned more information about the dwarf star at the centre of the Trappist-1system, as well as improved measurements of the size and mass of each planet, and the composition of their atmospheres. "So far, no sign allows us to say that they are not habitable", said University of Birmingham astronomer Amaury Triaud, the co-author of a study on the subject.

TRAPPIST-1 is named for the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile, which discovered two of the seven planets we know of today - announced in 2016. A year on, we are reporting our results. "Thanks to our efforts the TRAPPIST-1 planets are becoming the best-studied worlds outside the Solar system", stated Triaud.

The U.S. space agency reports in a news release that researchers have found that some of the planets have as much as 250 times more water than can be found here on Earth.

By comparison the oceans account for just 0.02 per cent of the mass of the Earth. For instance, five of the planets don't possess an atmosphere consisting of hydrogen and helium, like that of Neptune or Uranus.

Combined with data on their position relative to the star, the authors conclude that the non-rocky material in b is nearly certainly in the atmosphere-if it has any water, it's going to be in the form of water vapor, which would neatly explain its low density. But, more study needs to be done on that planet.

"The TRAPPIST-1 planets are so close together that they interfere with each other gravitationally, so the times when they pass in front of the star shift slightly", he said.

"All seven planets remarkably resemble Mercury, Venus, our Earth, it's Moon, and Mars".

"Although Hubble did not find evidence of hydrogen, we suspect the planetary atmospheres could have contained this lightweight gaseous element when they first formed", they said.

"The five planets are b, c, d, e, and f". This identification will be carried out by new observations. "But the telescope is really working at the limit of what it can do", adds co-author Hannah Wakeford from the Space Telescope Science Institute, illustrating both the power and limitation of Hubble. "Eliminating one possible scenario for the makeup of these atmospheres allows the Webb telescope astronomers to plan their observation programs to look for other possible scenarios for the composition of these atmospheres". Previously, scientists had discovered from the research that out of those seven TRAPPIST-1 planets three planets (e, f, g) are revolving in the habitable zone of the star.

Since then, the Hubble Space Telescope has been used to capture faint tell-tale light signals as the planets passed in front of their star, according to the Daily Mail.

This chart shows, on the top row, artist concepts of the seven planets of TRAPPIST-1 with their orbital periods, distances from their star, radii, masses, densities and surface gravity as compared to those of Earth.

The planets may also be tidally locked, meaning the same face is always pointing towards the star.

At present, according to scientists, it is impossible to know exactly how each planet is.

What might these planets be like?

The team looked to the planets' transits across the star. In our own solar system, the Moon and Mars have almost the same density, yet their surfaces appear entirely different.

TRAPPIST-1b, the innermost planet, is likely to have a rocky core, surrounded by an atmosphere much thicker than Earth's. Like 1c, it seems to have a relatively sparse atmosphere. The study also revealed that TRAPPIST-1d is the lightest of the planets, almost 30 percent the mass of Earth. Scientists are uncertain whether it has a large atmosphere, an ocean or an ice layer - all three of these would give the planet an "envelope" of volatile substances that would make sense for a planet of its density. It's the only planet in the system slightly denser than Earth.

The next step will be to explore the Trappist system with Nasa's James Webb Telescope, which will be able to determine for certain whether the planets have atmospheres and, if so, if they can provide the right conditions for liquid water to exist on the surface. In terms of size, density and radiation it receives from its star, it has the greatest resemblance to the Earth.

Meanwhile, F, G and H are the coldest planets and are expected to have water "in the form of ice". Webb will probe deeper into the planetary atmospheres, searching for heavier gases such as carbon dioxide, methane, water and oxygen.

Other reports by

Discuss This Article