Astronomers have glimpsed what could be an unknown planet orbiting one of the closest stars to Earth.
The researchers spotted the bright spot near Alpha Centauri A, a pair of stars revolving around each other so strong that they appear as one in the southern constellation Centauri. The stars form what is known as the binary system 4.37 light-years away, a simple stone’s throw in cosmic terms.
So provisional is the observation that scientists refer to it only as a “candidate planet”, aware that the bright speck in the darkness of space may be a test of alien asteroids, dust streaks or, more prosaically, an unforeseen error in your equipment. .
“We’ve spotted something,” said Pete Klupar, the chief engineer of the advanced initiatives, which are a series of space projects funded by Yuri Milner, a Silicon Valley-based entrepreneur. “It could be a machine artifact or a planet, or it could be asteroids or dust.”
The international team observed the star as part of the “Near Earths in the Alpha Centauri Region” (Near) experiment, supported by Breakthrough Watch, an effort to find and study rocky planets the size of Earth around of Alpha Centauri and other nearby stars.
To search for planets around the star, astronomers used the Very Large Telescope, or VLT, operated by the Southern European Observatory from Cerro Paranal in the Atacama Desert in Chile. The scientists received the help of a new coronograph on the instrument that blocks the light of the Alpha Centauri, which facilitates the detection of worlds in orbit.
Klupar compares the device to the disappearance of the sun with a thumb within arm’s reach. The procedure allows for unprecedented sensitivity to the direct image of planets beyond the solar system. “We try to see a flashlight right next to a lighthouse,” he said.
Writing in Nature Communications, the team described how the 100-hour infrared observations in May and June 2019 revealed a bright spot they have not been able to explain. If confirmed as a planet by further observations, the observation would be the first to directly imagine an exoplanet around a nearby star.
“A lot of people say that planets can’t form on this type of track and that’s one of the reasons we’re cautious about saying it’s actually a planet. But if so, it would be about the size of Neptune, ”he added. The planet would be in the habitable zone of the star, where temperatures allow liquid water to form, and it would take about a decade to complete an orbit.
Neptune is about four times the size of Earth and has no solid surface. Instead, it has an Earth-sized core wrapped in a thick soup of water, ammonia and methane, the latter gas making it blue like Uranus.
Professor Beth Biller, who studies exoplanets at the University of Edinburgh’s Institute for Astronomy, said the researchers had “an interesting candidate,” but they were right to be cautious.
“Independent and independent detection will be required to really confirm it,” he said. “If confirmed, it could be a detection of the dust disk around the star or a real planet. Both would be very interesting results.”
Klupar said the team wanted to look back later this year to see if the candidate planet had moved to where the predictions suggest it should be. But he said new observations might not be possible with the coronavirus pandemic still raging.