A cold 'super-earth' can live around a nearby star

A planet three times more massive than the Earth may be hiding around the second star system closest to our cosmic neighborhood. Astronomers say they have found evidence of a so-called "super-Earth" around the famous Barnard star, a small, pale dwarf star located less than six light-years away. Although we do not know what this potential planet looks like, its proximity makes it an excellent target for future telescopes to study in the long-standing pursuit of extraterrestrial life.

This discovery, detailed today in the newspaper Nature, mark another planet found around a relatively close star. In 2016, astronomers claimed to have found a small rocky world around Proxima Centauri, the closest star to our solar system, just 4.2 light years from Earth. Now, this makes two possible planetary systems next to each other, further reinforcing the idea that our galaxy could be flooded with planets.

Plus, a planet around Barnard's star is a planet we could see soon. Although we have found thousands of planets outside our solar system, most of these worlds – called exoplanets – are usually impossible to see directly with our current telescopes. They are so far away that they are completely submerged by the starlight of their host. But planets around nearby stars – like Barnard's star – are easier to detect for our instruments. One day, we could potentially distinguish the light reflected by this planet from the light of its host star, especially as larger and more sophisticated observatories are in service in the 2020s.

"This is the main advantage of finding a planet so close," says Ignasi Ribas, astronomer at the Institute of Space Sciences in Spain and lead author of the study, The edge. "If we someday have the hope of being able to directly visualize the planets, it is because they are really close planets because you have to separate them from the light of their star."

Image: IEEC / Science-Wave

Barnard's star has long intrigued astronomers. Because of its relatively short distance from us, it seems to move in the sky faster than any other star. The star takes its name from E. E. Barnard, the American astronomer who measured this movement in 1916. Barnard's star is also a very small and confusing type of star called a red dwarf. In fact, it represents only 14% of the mass of our own Sun and it is so weak that you need a telescope to see it. Although they are among the smallest stars in the galaxy, red dwarfs are also the most common. In recent decades, astronomers have found more and more potentially habitable planets around these celestial objects.

Because of its proximity, Barnard's star has become a popular target for exoplanet hunters. In the 1960s, an astronomer by the name of Peter van de Kamp claimed to have found a Jupiter-sized world around Barnard's star after studying the movement of the Red Dwarf. At the time, it was a big complaint because we had not yet the good confirmation that the exoplanets already existed. But the conclusions were finally refuted and questioned by the telescope used by van de Kamp. Over the years, astronomers have dismissed the existence of planets in the habitable zone of the Barnard star, the region around a star where temperatures are ideal for water to exist in liquid form.

But this time, there may be something in orbit around the star just a little further away from the habitable zone. An international group of astronomers used data from 20 years of observing Barnard's star, taken with seven different telescopic instruments, to find evidence of a planet's existence. "We have collected nearly 800 observations, using the most accurate instrumentation in the world, just to see this little planet," said Ribas.

In particular, the team investigated how Barnard's star "flickered" over time – a technique used by astronomers to find exoplanets when they can not be seen. Since the exoplanets are drowned under the stars, astronomers must use intelligent and indirect methods to unravel the existence of a distant world. One method is to observe the passage of these planets between the host star and the Earth – what is called a transit – which slightly attenuates the light of the star. However, this planet does not transit, astronomers have studied the effect of the gravity of the planet on the star of Barnard. Even small planets can push and fire on a nearby star, creating tiny "swings" that we can measure from Earth.

Ribas and his team have noticed a trend in the oscillations of Barnard's star over the past 20 years, indicating a planet revolving around the star every 233 days. They estimate that the exoplanet is about 3.2 times the mass of the Earth and that its distance from the star is located in what is called the snow line. It is the region around a star where gases can condense into solids and the water turns into snow and ice. This area is about four times farther from the habitable area and many astronomers believe that it is the best place around a star for planet formation. "If it's real, then it would be a strong confirmation, one of our main theories of planet formation," said Keivan Stassun, astronomer at Vanderbilt University. The edge.

Picture of Mr. Kornmesser / ESO

We have not yet seen this planet directly, and although Ribas is confident in the conclusions of his team, he admits there is always a small chance that the flickering they saw may be explained in another way . "We are not 100% sure that the signal comes from a planet, but at 99.2%," he says. "But being as confident is enough to claim the detection of the planet."

The next obvious step is to get a signal from the planet itself, which could be possible soon. "At this very close distance, we should be able to separate light from the planet from starlight," says Stassun. To be able to see the light of an exoplanet is enormous because we can then study what is happening in the atmosphere of the planet. And the gases that surround a planet could tell us a lot about what's on the surface – maybe even whether life is present or not.

As this planet is close to the snow line, it is not a particularly promising candidate in the quest for extraterrestrial life. But it will be a good exoplanet for astronomers to study. This could help them refine their techniques to distinguish planets from stars and determine the content of their atmosphere. And the tools to do it should be online by the next decade. The NASA James Webb Space Telescope, due to be launched in 2021, should be sensitive enough to deepen the study of the planet. And large telescopes, such as the thirty-meter telescope planned for Hawaii, may also be able to spot the planet.

Ribas says the best bet for seeing this world is a future telescope that NASA is working on, called WFIRST. The space telescope could potentially study the big planets with the help of a special instrument called a coronagraph, which helps block starlight. Due to budget constraints, NASA has sought ways to reduce the cost of the coronograph by reducing the number of masks and filters used by the instrument, according to News from the space. But Ribas says that a coronagraph is the surest way to see this world. "It would be very effective in removing light from the stars," he says. "If this type of machinery is in place, we can image the planet."

For the moment, Ribas and his team will continue to monitor the flickering of Barnard's star to strengthen their claim – a claim that now aligns with many science fiction works. Stories like The Galactic Traveler's Guide and The garden of Rama The stars around the Barnard star are planets serving as relays for interstellar travelers. "For decades, it has been a favorite imaginary destination of human civilization in the future," said Stassun. "How tempting is this neighboring star to be a neighboring solar system."