At least one of the seven rocky planets circling the dwarf star TRAPPIST-1 may be an ocean world, scientists say, creating updated climate models for the exoplanets.
Researchers from the University of Washington in the United States said that because of the extremely hot, bright early star phase, all seven of the star's worlds may have evolved as Venus.
Every wounded ocean the planets may have evaporated, leaving behind a dense, uninhabitable atmosphere.
"We are modeling unfamiliar atmospheres not only by assuming that the things we see in the Solar System will look the same way around another star," says Andrew Linkovski, a PhD student at Washington University.
"We conducted this study to show how these different atmospheres might look," said Linkovski, lead author of the study, published in the Astrophysical Journal.
The TRAPPIST-1, at 39 light-years, has about nine percent of the mass of the sun and about 12 percent of its radius.
The relatively cool "M dwarf" star, the most common type in the universe, has a radius slightly larger than the planet Jupiter, although it is much larger in the mass.
All seven of the planets of TRAPPIST-1 are about the size of the Earth, and three of them – the planets designated e, f and g – are believed to be in their habitable zone, that is space around the star, liquid water on its surface, thus giving life to chance.
TRAPPIST-1 d moves along the inner edge of the habitable zone, and further away, TRAPPIST-1h, orbits directly behind the outside of that area.
"This is a whole series of planets that can give us insight into the evolution of the planets, especially around a star that is very different from ours, with a different light coming from it," Linkovski said.
Radiation and chemical models of the team create spectral or wavelength signatures for every possible atmospheric gas, allowing observers to better predict where to look for such gases in the atmosphere of the exoplanet.
Researchers have said that when the gas traces are actually discovered by the Webb telescope or other, astronomers will someday use the observed impacts and hang in the spectra to get an idea of what gases are available – and compare that we work like ours for to say something about the composition of the planet, about the environment, and perhaps about its evolutionary history. "
He said people are used to thinking about the planet's habitation around stars like the sun.
"But the stars of the Dwarves M are very different, so you really have to think about the chemical effects on the atmosphere and how this chemistry affects the climate," Linkovski said.
TRAPPIST-1 b, closest to the star, is a blazing world too hot, even for clouds of sulfuric acid as they are in Venus.
Planets c and d get a little more energy than their star than Venus and Earth make from the sun and can be similar to Venus, with a dense, uninhabitable atmosphere.
TRAPPIST-1e is the most probable of the seven households of liquid water on a moderate surface and would be an excellent choice for further research in terms of occupancy.
The outer planets f, g and h can be similar to Venus or frozen, depending on how much water has formed during the evolution of the planet.
Linkavski said that in fact all or all of the planets of TRAPPIST-1 could be similar to Venus, with any water or oceans long burned.
He explained that when water evaporates from the surface of the planet, ultraviolet light from the star destroys water molecules, releases hydrogen, which is the lightest element and can avoid gravity on the planet.
This can leave a lot of oxygen that can remain in the atmosphere and permanently remove the water from the planet. Such a planet may have a thick oxygen atmosphere – but not generated by life and other than anything that is still being observed.