2024-07-13 00:53:49
A celestial body that has been in the field of view of astronomers for years may turn out to be the first ocean planet discovered outside the Solar System using the James Webb Space Telescope, AFP reported, referring to a publication in the Astrophysical Journal Letters. (Astrophysical Journal Letters).
The object LHS 1140b has been studied from all possible angles since its discovery 48 light years from Earth in the constellation Cetus in 2017. It enriches the catalog of several thousand exoplanets – celestial bodies that orbit a star other than our Sun.
However, only a handful of them are considered to be potentially “habitable”, i.e. they are likely to harbor a form of life on a rocky planet neither too close nor too far from their star.
Such a planet must have the right conditions – temperature and pressure – to allow water to be in a liquid state and remain so, notes Charles Cadillo, a doctoral candidate in astrophysics at the Canadian Trottier Institute for Exoplanet Research.
The study, conducted by a team from the University of Montreal, confirms first of all that LHS 1140b is a super-Earth with a mass about 5.6 times that of our blue planet, and not a mini-Neptune.
Initial observations put the celestial body right between these two types of exoplanets – a mini-Neptune with the characteristic density, a ball of rock with a very dense atmosphere of hydrogen and helium, or a super-Earth, or even an “ocean planet with a slightly smaller rocky core, but offset by a shell of water,” Cadillo explains.
The James Webb Space Telescope made the decision possible by observing the planet’s atmosphere as it passes in front of its star. The lack of signals suggesting the presence of hydrogen or helium rules out the mini-Neptune scenario.
The density of LHS 1140b suggests that “the planet actually has large amounts of water,” according to Martin Turbet, co-author of the study and a researcher at France’s National Center for Scientific Research (CNRS).
We are talking about “phenomenal” amounts of water. Water in Earth’s oceans makes up only 0.02 percent of its mass, while that of LHS 1140b would make up between 10 and 20 percent of its mass. However, in what form remains to be seen.
Here, scientists again raise the question of the planet’s atmosphere. “We don’t have direct evidence that it has an atmosphere, but there are indications that it does,” says Turbe.
The first advantage is that LHS 1140b is slightly heated by the rays of its red dwarf star, with “expected surface temperatures that should be quite comparable to those of Earth or Mars,” he told AFP.
Depending on whether the potential atmosphere contains few or many greenhouse gases such as carbon dioxide, the water surface will either be icy or not. There may even be a liquid ocean on the part of the planet exposed to the rays of its star.
“Unless this ocean is hidden under a layer of ice, a bit like the icy moons Ganymede, Enceladus or Europa, which orbit the giant planets of the Solar System – Jupiter and Saturn,” added Turbe.
Additional observations are of interest to the researchers. Observations made by spectrometers on the James Webb telescope showing the potential presence of nitrogen must be confirmed, explains Charles Cadillo. This gas, along with oxygen, is ubiquitous in the air that humans breathe on Earth.
The Montreal team is campaigning for further observations of LHS 1140b with the help of James Webb.
“We need at least a year to confirm that LHS 1140b has an atmosphere, and probably another two or three to detect carbon dioxide,” said astrophysicist and study co-author René Doillon, quoted by BTA.
As for whether we will draw water from this source, it is pointless to dream, since it is located about 450,000 billion kilometers away.