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In a first, atmosphere found around Earth-like planet

Astronomers have for the first time detected an atmosphere around an Earth-like planet just 39 light years away, a significant step towards the detection of life beyond our solar system.

Scientists, including those from Max Planck Institute for Astronomy in Germany, studied the planet known as GJ 1132b, which is 1.4-times the size of our planet.

They imaged the planet’s host star, GJ 1132, and measured the slight decrease in brightness as the planet and its atmosphere absorbed some of the starlight while passing directly in front of their host star.

Too much like our Earth

The detection of an atmosphere around the super-Earth GJ 1132b marks the first time an atmosphere has been detected around a planet with a mass and radius close to Earth’s mass and radius (1.6 Earth masses, 1.4 Earth radii), researchers said.

“With the present observation, we have taken the first tentative steps into analysing the atmosphere of smaller, lower-mass planets that are much more Earth-like in size and mass,” researchers said.

GJ 1132b orbits the red dwarf star GJ 1132 in the southern constellation Vela, at a distance of 39 light years from us.

The team used the GROND imager at the 2.2-m ESO/MPG telescope of the European Southern Observatory in Chile to observe the planet simultaneously in seven different wavelength bands.

Transiting planet

GJ 1132b is a transiting planet: From the perspective of an observer on Earth, it passes directly in front of its star every 1.6 days, blocking some of the star’s light.

The size of stars like GJ 1132 is well-known from stellar models. From the fraction of starlight blocked by the planet, astronomers can deduce the planet’s size — in this case around 1.4 times the size of the Earth.

The new observations showed the planet to be larger at one of the infrared wavelengths than at the others.

This suggests the presence of an atmosphere that is opaque to this specific infrared light (making the planet appear larger) but transparent at all the others.

Different possible versions of the atmosphere were then simulated by team members at the University of Cambridge and the Max Planck Institute for Astronomy.

Methane-rich, a ‘water world’

According to those models, an atmosphere rich in water and methane would explain the observations very well.

Observations to date do not provide sufficient data to decide how similar or dissimilar GJ 1132b is to Earth.

Possibilities include a “water world” with an atmosphere of hot steam, researchers said.

“GJ 1132b provides a hopeful counterexample of an atmosphere that has endured for billion of years. Given the great number of M dwarf stars, such atmospheres could mean that the preconditions for life are quite common in the universe,” they said.

The research was published in the Astronomical Journal.

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