A little over a decade ago, astronomers found a large gap between two belts circling Vega, hinting that the nearby star probably hosts several exoplanets.
Then in 2021, other researchers saw what they believed was perhaps a signal of a Neptune or Jupiter-like gas giant orbiting extremely close to the star. Surely, they thought, when the ultra-sensitive James Webb Space Telescope launches into space, they'll finally get the definitive proof of a planet.
But after pointing Webb at the target, and gathering more data from the Hubble Space Telescope, NASA scientists have not seen what they thought they'd find. The latest observations seem to suggest that the 1997 sci-fi film Contact, based on an older book by Carl Sagan, could have had it right after all — that there's nothing out there around Vega but a swirl of debris.
"The Hubble and Webb observations together provide so much more detail that they are telling us something completely new about the Vega system that nobody knew before," George Rieke, one of the researchers based at the University of Arizona, said in a statement.
Vega, set in the summer constellation Lyra, is about 25 light-years, or 150 trillion miles, away from Earth. It's an A-type star: young, robust, and spinning much faster than the sun. This thing, about 450 million years old, is 40 times brighter than the sun, beaming sizzling blue-white light. Its swift rotation, fully turning every 16 hours, makes it a challenging target for scientists, who want to track its motion and look for tugs from potential planets.
The new study, to be published as two papers in The Astrophysical Journal, was based on a highly detailed look at Vega's 100-billion-mile-wide debris disk, which faces Earth. In the past, this disk was thought to be a circle of planet-forming material; indeed, in our own solar system, planets emerged from such a disk once centered on the sun, though now that disk is long-gone.
"The Vega disk is smooth, ridiculously smooth."
Astronomers were shocked when Webb and Hubble showed nothing to suggest any large planets were busy at work, plowing away dust, which would be typical in a star system that's Vega's age, only about 10 percent of the sun's. Usually these nubile stars are surrounded by lots of dust, enriched by frequent collisions of asteroids and comets.
Hubble detects material the size of smoke particles, and Webb can pick up particles as miniscule as a grain of sand, according to NASA. Yet neither showed signs of worlds pushing and clearing dust away, a clue scientists seek when trying to determine if a star has planets. The discovery of a pancake disk without obvious traces of planets is forcing them to rethink why Vega's system isn't what they expected, and it could offer new insights into planet formation, generally.
"It's unlike other circumstellar disks we've looked at," said Andras Gáspár, another member of the research team, in a statement. "The Vega disk is smooth, ridiculously smooth."
Despite its smoothness, the disk does appear to have a slight, subtle gap far out from the star, about double the distance of Neptune from the sun. The researchers say that rules out the possibility of planets down to at least the mass of Neptune.
Ironically, Vega is renowned for opening the eyes of astronomers to the idea that other stars could host planets, and that the material orbiting a star — seemingly the building blocks for making planets — could host life.
"Vega continues to be unusual," said Schuyler Wolff, lead author of the study, in a statement. "The architecture of the Vega system is markedly different from our own solar system where giant planets like Jupiter and Saturn are keeping the dust from spreading the way it does with Vega."
Topics NASA
