Astronomers find Earth's twin 41 light years away

Astronomers using the James Webb Space Telescope (JWST) have discovered a rocky planet 41 light-years from Earth that may have an atmosphere.

The results of a new study by British scientists from the Bristol and University of St. Andrews indicate, that the planet Trappist-1e is located in the so-called “The “Goldilocks Zone” around the parent star, where the temperature allows liquid water to exist on the surface of the planet. If the data on Trappist-1e is confirmed by further observations, this planet may become the first to have a detectable atmosphere. 

Exoplanets orbiting their stars outside the solar system and which may contain liquid water, must also have an atmosphere with a sufficient greenhouse effect. The greenhouse effect creates additional heat by absorbing and emitting gases in the atmosphere and helps prevent water from evaporating into space.

Trappist-1e is one of the seven rocky planets that revolve around a small, relatively cold star of the red dwarf Trappist-1. Currently, most of the discovered rocky exoplanets orbit similar red dwarfs with temperatures significantly lower than our Sun. 

This is not due to the fact, that planets orbiting stars similar to the Sun, are rare, with technical limitations, that make it easier to find and study exoplanets orbiting smaller stars. Red dwarfs have many advantages in measuring the properties of planets orbiting them.

Since red dwarfs are colder, they are inhabited by habitable zones where the temperature allows liquid water to exist, are located much closer to our solar system. Thus, a year on a rocky planet with a temperature, like the Earth, orbiting a red dwarf, may be only a few days or a week, compared to 365 Earth days. 

One way to detect such exoplanets, is to measure the slight attenuation of light from the planet as it passes by on the disk of a star. Because planets, orbiting red dwarfs, make a complete revolution faster, astronomers can observe more passes in a short period of time, making data collection easier.

During the transit, astronomers can measure the absorption of gases in the planet’s atmosphere.  Absorption is the process by which certain gases absorb light at different wavelengths, blocking it from passing through. This allows scientists to determine which gases are present in the atmosphere.

Moreover, the smaller the star, the more of its light is blocked by the planet’s atmosphere during passage. Therefore, red dwarfs provide one of the best opportunities to search for planets with atmospheres.

Three planets from the Trappist-1 system — Trappist-1d, Trappist-1e, and Trappist-1f (the third, fourth, and fifth planets from the star), are located in the Goldilocks Zone. JWST systematically searches for atmospheres on the planets of the Trappist-1 system from 2022. 

The star-corrected atmospheric transmission spectrum of Trappist-1e can be represented either by blue lines indicating the presence of an atmospheric signal or by an orange straight line indicating the complete absence of an atmosphere. The white color shows how these two options overlap, and hence the problem of interpreting the initial observations.

The findings for the three planets closest to the red dwarf Trappist-1 indicate, that these worlds are likely to have a rocky landscape with a thin atmosphere at best. However, planets located farther from the star, which are subject to less bombardment by radiation and powerful starbursts, can still potentially have atmospheres. 

Astronomers envision two possible explanations for what is happening on Trappist-1e. The first assumption, is that the planet has a so-called secondary atmosphere, containing heavy molecules, such as nitrogen and methane.

However, the available observations are insufficient to rule out the possibility, that Trappist-1e is a bare rocky planet without an atmosphere. To determine whether the planet Trappist-1e is habitable, it is necessary to measure the concentration of greenhouse gases such as carbon dioxide and methane.

Currently, 15 more transits of Trappist-1e are underway and should be completed by the end of 2025. In future observations, the astronomers plan to change their strategy to include the planet Trappist-1b — naked and rocky. This will allow them to use observations of Trappist-1b to more accurately track hot and cold active regions on the star. Any excessive gas absorption observed only during Trappist-1e transits will be due solely to the planet’s atmosphere.

The results of the study are published in the journal Astrophysical Journal Letters

Source: The Conversation; ZMEScience