Astronomers have discovered atmospheres around exoplanets before. But those planets were much more massive than Earth. Think gas giants like Jupiter or super-Earths eight times larger than our home. GJ 1132b isn’t that much bigger than Earth. Its mass clocks in at just 1.6 Earth masses.
A team of astronomers, led by Keele University’s Dr. John Southworth, trained the 2.2 m ESO/MPG telescope in Chile at the planet located 39 light-years from Earth. Every 1.6 days, GJ1132b slides between Earth and its host star (M dwarf). The slight dip in brightness caused by the transiting planets can offer all kinds of data including mass, orbit, and in this case, atmosphere.
“While this is not the detection of life on another planet, it’s an important step in the right direction: the detection of an atmosphere around the super-Earth GJ 1132b marks the first time that an atmosphere has been detected around an Earth-like planet other than Earth itself,” says Southworth.
Finding GJ 1132b’s atmosphere
Southworth’s team used the GROND imager at the ESO/MPG telescope in Chile to observe nine transits. GROND stands for Gamma-Ray Burst Optical/Near-Infrared Detector. Like its name suggests, GROND usually glances at gamma-ray bursts. Evidently, the instrument’s seven filter bands are also great at looking for atmospheres.
Each of the seven wavelengths gives astronomers a slightly different look at the planet. From optical to near-infrared. In one of the seven wavelengths (z-band), GJ 1132b appears larger. That suggests an atmosphere that is opaque at this specific light, but transparent in the other six wavelengths.
Team members from the University of Cambridge and the Max Planck Institute for Astronomy simulated a series of possible atmospheres. The best explanation from these models is an atmosphere rich in water (hot steam) and methane.
A small win for M dwarf stars
M dwarfs are everywhere. There is one problem, though. Especially for life. M-dwarfs tend to be very active stars spewing solar flares and solar radiation often. This radiation often strips nearby planets of their atmospheres. And without them, the worlds become hot, barren rocks.
But GJ 1132b shows us that not all worlds lose their atmosphere. Some worlds can endure the onslaught of solar radiation for billions of years. With M dwarf stars being the most common type of star, it raises the possibility that atmospheres around them are common.
A planet orbiting one of these stars would need it too. If a planet is located in the habitable zone of an M dwarf star, it’s likely tidally locked. That means one side of the planet is always facing the star. One side sits in continuous daylight, the other in darkness. The temperature differences between the two sides would be enormous. Unless there’s a thick enough atmosphere to circulate the heat.
Still waiting for the James Webb Space Telescope
Astronomers are making due with what they have, but what they need are better telescopes. That’s where ESO’s Very Large Telescope and the James Webb Space Telescope come in. Look for GJ 1132b to be near the top of the list of the first worlds these new telescopes look at.
The James Webb Space Telescope will finally launch in October 2018. Six months after launch, the telescope will be ready for primetime. Soon after, we can expect the first images back on Earth. Astronomers and space fans around the world will be crossing their fingers for the first exoplanet with an atmosphere rich in oxygen.