Tag: TRAPPIST-1

TRAPPIST-1 Planets Probably Rich In Water

Planets around the faint red star TRAPPIST-1, just 40 light-years from Earth, were first detected by the TRAPPIST-South telescope at ESO’s La Silla Observatory in 2016.

In the following year further observations from ground-based telescopes, including ESO’s Very Large Telescope and NASA’s Spitzer Space Telescope, revealed that there were no fewer than seven planets in the system, each roughly the same size as the Earth.

They are named TRAPPIST-1b,c,d,e,f,g and h, with increasing distance from the central star.

Further observations have now been made, both from telescopes on the ground, including the nearly-complete SPECULOOS facility at ESO’s Paranal Observatory, and from NASA’s Spitzer Space Telescope and the Kepler Space Telescope.

A team of scientists led by Simon Grimm at the University of Bern in Switzerland have now applied very complex computer modelling methods to all the available data and have determined the planets’ densities with much better precision than was possible before.




Simon Grimm explains how the masses are found: “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.

“These shifts depend on the planets’ masses, their distances and other orbital parameters. With a computer model, we simulate the planets’ orbits until the calculated transits agree with the observed values, and hence derive the planetary masses.”

Team member Eric Agol comments on the significance: “A goal of exoplanet studies for some time has been to probe the composition of planets that are Earth-like in size and temperature.

“The discovery of TRAPPIST-1 and the capabilities of ESO’s facilities in Chile and the NASA Spitzer Space Telescope in orbit have made this possible — giving us our first glimpse of what Earth-sized exoplanets are made of!

The measurements of the densities, when combined with models of the planets’ compositions, strongly suggest that the seven TRAPPIST-1 planets are not barren rocky worlds.

They seem to contain significant amounts of volatile material, probably water, amounting to up to 5% the planet’s mass in some cases — a huge amount; by comparison the Earth has only about 0.02% water by mass!

TRAPPIST-1b and c, the innermost planets, are likely to have rocky cores and be surrounded by atmospheres much thicker than Earth’s.

TRAPPIST-1d, meanwhile, is the lightest of the planets at about 30 percent the mass of Earth. Scientists are uncertain whether it has a large atmosphere, an ocean or an ice layer.

Scientists were surprised that TRAPPIST-1e is the only planet in the system slightly denser than Earth, suggesting that it may have a denser iron core and that it does not necessarily have a thick atmosphere, ocean or ice layer.

It is mysterious that TRAPPIST-1e appears to be so much rockier in its composition than the rest of the planets.

In terms of size, density and the amount of radiation it receives from its star, this is the planet that is most similar to Earth.

TRAPPIST-1f, g and h are far enough from the host star that water could be frozen into ice across their surfaces.

If they have thin atmospheres, they would be unlikely to contain the heavy molecules that we find on Earth, such as carbon dioxide.

Astronomers are also working hard to search for further planets around faint red stars like TRAPPIST-1. As team member Michaël Gillon explains: “This result highlights the huge interest of exploring nearby ultracool dwarf stars — like TRAPPIST-1 — for transiting terrestrial planets.

“This is exactly the goal of SPECULOOS, our new exoplanet search that is about to start operations at ESO’s Paranal Observatory in Chile.

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Pass it on: Popular Science

What Would Life Be Like On The TRAPPIST-1 Planets?

The TRAPPIST-1 system is home to seven planets that are about the size of Earth and potentially just the right temperature to support life.

So how would life on these alien worlds be different than life on Earth? Here are some of the major differences.

Amazing night-sky views

Perhaps one of the most dramatic things that visitors to the TRAPPIST-1 system would notice is the view of the other six planets in the sky.

In some cases, a neighboring planet might appear twice as large as the full moon seen from Earth.

All seven of the known planets in the TRAPPIST-1 system orbit closer to their star than Mercury orbits the sun.




The innermost planet and the outermost planet are almost 30 times closer together than Earth and Venus at their largest separation.

The reason these seven planetary siblings can fit into such tight orbits is because their parent star is an ultracool dwarf star. It’s about 2,000 times dimmer than the sun, and only slightly larger than the planet Jupiter.

Three of the known planets orbit the star in what’s known as the “habitable zone,” or the region around a star where the planet could have a surface temperature right for liquid water.

The position of the habitable zone is different around each star — on a very dim star like TRAPPIST-1, which radiates significantly less heat than the sun, the habitable zone lies much closer to the star.

But there’s no guarantee that a planet in the habitable zone of TRAPPIST-1 can host liquid water on its surface.

Without an atmosphere, water won’t remain a liquid in space. For example, on comets, water ice sublimates directly into a vapor when it is heated by the sun.

Perpetual twilight

Even though the seven known planets in the TRAPPIST-1 system orbit extremely close to their parent star, the natural lighting on these planets would seem very dim to a human visitor.

Ultracool dwarf stars produce significantly less radiation than sun-like stars, and most of TRAPPIST-1’s light is radiated in the infrared wavelengths rather than visible wavelengths, according to Amaury Triaud of the Institute of Astronomy at the University of Cambridge in England, a co-author on the paper describing the discovery.

Short years, eternal days (and nights)

The TRAPPIST-1 planets take almost no time at all to make one complete orbit around their parent star. Six of the planets make a complete an orbit in anywhere from 1.5 to 12.4 days.

That means one “year” (or what scientists call the orbital period) on most of these planets is less than two weeks on Earth. But the orbital period of these planets is slightly upset by their neighbors.

Even though the years are short in the TRAPPIST-1 system, the days would be very long — almost eternal, because the according to the scientists behind the discovery, it’s very likely the seven planets are tidally locked, meaning that one side of each planet is always facing the star.

The moon is tidally locked to Earth, which is we see only one side of our lunar companion (at least from the ground).

There’s some debate about whether or not a tidally locked planet could host life.

Some tidally locked planets might be uninhabitable because the side facing the star would become extremely hot, while the other side would grow extremely cold.

But some models show that if the planet’s atmosphere can dissipate heat across the planet’s surface, then life could still find a welcoming home there.

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Pass it on: New Scientist