An international team, including researchers from McGill University, recently discovered what could be a second Earth. Located 40 light-years away, Gliese 12b is very similar in size to Earth, has moderate temperatures, and offers hope that liquid water may exist. In astronomy, if you say water, you mean life. Gliese 12b could potentially host some form of life. Native, or imported.
“We are not yet able to detect life,” Vigneshwaran Krishnamurthy quickly explains, giving moderate hopes. The astronomer and aerospace engineer at McGill’s Trottier Space Institute explains that his team still has to try to find out if the planet has an atmosphere. “If this planet has no clouds, nothing to reflect sunlight, the temperature should be between 50 and 70 degrees Celsius. These are the temperatures we would expect to find,” he explains. “But if there are clouds, it could drop to our moderate temperatures.” The likelihood of liquid water on the surface of the exoplanet depends on these temperatures, which are similar to our own.
Another important element is the composition of Gliese 12b’s possible atmosphere. Mr Krishnamurthy reminds us of the recipe for life. “We need water, oxygen and complex molecules in the atmosphere, not just hydrogen and helium. You also need something heavier, like carbon dioxide and methane. Interestingly, if all the necessary ingredients for life are present and the recipe is successful, an additional element should appear in the atmosphere, a biosignature that we all know: methane. “There is a huge amount of methane in our atmosphere, which is produced by life forms. So, if there were no life forms, methane production should not be as high as it is in our atmosphere,” the astronomer explains.
In the case of Gliese 12b, current technology doesn’t make it possible to detect even microbes, let alone humans or aliens, Vigneshwaran Krishnamurthy recalls. He insists that the atmospheric study by the team led by Japanese researchers Masayuki Kuzuhara and Akihiko Fukui won’t confirm the presence of life, but will only open up the possibilities, and see whether Gliese 12b could harbor or accommodate life as we know it.
star, dwarf star
The Sun around which Gliese 12b resides plays a big role in the significance of this discovery. Gliese 12, which gave Gliese 12b its incongruous name, is what we call a red dwarf. It is a star that is smaller and cooler than our Sun. As a result, the distance between the planet and Gliese 12, so that the temperatures are neither too hot nor too cold for the planet to accommodate liquid water, is smaller than that needed in our solar system. Interestingly, Gliese 12b takes only 12 days to orbit its star, while our Earth takes 365 days.
This difference allows scientists to observe the exoplanet every 12 days, because they need a planet in front of its star, in their line of sight, to be able to study it. “If we were to observe Gliese 12b five times, it would only take two months,” says Mr. Krishnamurthy, beaming. “For a planet like Earth, it would take five years.” Besides potentially finding a place to move humanity, as depicted in Christopher Nolan’s “Interstellar,” an Earth-like planet like Gliese 12b would allow us to better understand our own universe.
Mr Krishnamurthy’s point is that we have, through geology and mineral chemistry, data about the Earth as it was millions of years ago and its evolution. What we don’t have is a point of comparison. “We don’t know if the path that the Earth took is the path that any planet (with similar properties) would have taken,” the astronomer continues. Understanding a body that is very similar to Earth, and has an atmosphere that may have evolved differently, could give us insight into how other planets evolved, and even fill in gaps in our understanding of the Earth.
In addition, Gliese 12b enters the race for habitable exoplanets right at the top of the list. “Earth is the only planet we currently know of that has all the ingredients needed to support life,” says the researcher. Scientists around the world have yet to find a planet that supports life, and there is no evidence that any other planet has all the ingredients needed to support life. The scientific community has only a handful of candidate exoplanets to examine their atmospheres for traces of biosignatures. However, not as many boxes have been ticked as Gliese 12b. The scientist points out that for an exoplanet to be Earth 2.0, it must first have the right distance from its star so that temperatures are similar to ours. It must also have a similar size and mass to Earth so that gravity does not pull too much gas to its surface.
These criteria alone reduce the number of potentially habitable exoplanets to about a hundred, at most, out of the roughly 5,500 we know of. Then there is the presence and composition of an atmosphere. The fact that Gliese 12b is a stone’s throw from the stars is just icing on the cake, because it is by far the closest possible Earth 2.0 planet to us, and thus the first to be explored when technology allows. Migration to Gliese 12b is not for tomorrow. Although technology is improving faster and faster, it will be some time before we find a way to travel to another solar system. A journey that will not be insignificant, since it would take about 4,000 years to reach Gliese 12b.
The team behind the discovery is currently in the process of submitting applications to major space agencies, such as NASA or the Canadian Space Agency, so that they can use their telescopes next year to observe the atmosphere of Gliese 12b in great detail.
Caption and image: An international team, including researchers from McGill University, has recently discovered an exoplanet that could be a second Earth. This undated illustration provided by the European Space Agency depicts what another exoplanet, TRAPPIST-1, might look like. NASA, ESA, CSA, J. Olmsted (STScI), T. P. Greene (NASA Ames), T. Bell (BAERI), E. Ducrot (CEA), P. Lagage (CEA) via APNASA, ESA, CSA, J. Olmsted
