Over the past 30 years, astronomers have discovered more than 5,000 exoplanets, an eclectic world far from our stellar neighborhood. The latest may just be a baby.
In the journal The Astrophysical Journal Letters, scientists on Tuesday announced compelling evidence for a world that is only 1.5 million years old, making it one of the youngest planets ever discovered, and perhaps the youngest planet.
The world — Ophiuchus, 395 light-years from Earth — is so young that its components of gas and dust are still clumping together. The planet is a newborn, held in the arms of its parent star.
“It’s like looking back at our own past,” said study co-author Myriam Benisty, an astronomer at the Institute of Planetology and Astrophysics in Grenoble, France.
Because the suspected planet is shrouded in the material that made it, further telescopic observations are needed to confirm its existence. Assuming it’s not rock debris disguised as a planet, scientists can use it to better understand how worlds formed.
The torrent of newly discovered exoplanets has complicated or overturned long-standing theories of planet formation. But the asteroid’s location — firmly within a disk of primordial material around its star — supports the idea that most planets spend most of their time growing up in similar nurseries.
Anders Johansson, an astronomer at Lund University in Sweden who was not involved in the study, said the discovery of the celestial point suggests that “all planetary systems share a common formation process.” He said that despite the chaos of the universe, “there’s actually a lot of order” when it comes to making planets.
The team of scientists used the Atacama Large Millimeter/submillimeter Array (ALMA), an array of 66 antennas working synergistically in Chile, to gather evidence of this extremely young world. Gas and dust orbit certain stars in so-called circumstellar disks. This material clumps together to form planets within these disks, emitting radio waves that ALMA can detect.
Last year, Dr. Benisty and her colleagues used ALMA to unequivocally detect the first A halo of gas and dust orbiting an exoplanet: A planet-orbiting foundry is still making the world it envelopes, and maybe a few moons.
For the latest study, they pointed ALMA at AS 209, a star a little heavier than the Sun. It’s only 1.5 million years old and has only recently started burning hydrogen — the star equivalent of a toddler uttering its first words.
The circumstellar disk of AS 209 was found to have several gaps. During one such gap, ALMA detected the radio wave signature of a planet-making storm, gas that may be surrounding a Jupiter-like world still under construction.
The planet’s exact age won’t be resolved anytime soon, but it’s likely very similar to its newborn star. But its youth isn’t the only thing that piques the interest of astronomers. It’s also puzzlingly far from its star. Neptune is the outermost planet in our solar system, about 2.8 billion miles from the sun. The exoplanet is nearly 19 billion miles from its own star.
This raises questions about our own predicament.
The size of the debris disk that formed Earth and other planets is uncertain. “Perhaps the disk is only slightly larger than Neptune’s orbit, which is why Neptune is the outermost planet,” Dr Johansen said. But maybe our planetary manufacturing hub is more like AS 209. If so, “nor can we rule out that our own solar system has a planet beyond Neptune,” he said — perhaps a hypothetical Planet 9, which some astronomers suspect, lingering in the distant darkness.
Over the next few days, the James Webb Space Telescope will determine the planet’s nascent mass and study its atmospheric chemistry. By creating a detailed portrait of one of the youngest worlds known to science, these observations will bring us one step closer to answering the ultimate question: Where do we come from? “