There is no evidence of giant planets around Vega, one of the brightest, most famous and most important stars in the night sky, according to new research. Using the Hubble and James Webb Space Telescopes, a team of astronomers at the University of Arizona, Tucson, studied a disk of debris about 100 billion miles in diameter around the iconic star. They discovered a perfect circle, with no disruptions, meaning no planets. For astronomers, that’s hugely puzzling.
Vega: ‘Uniquely Smooth’ Disk
Just 25 light-years from the solar system, Vega is 455 million years old, a tenth of the age of our sun, but 40 times brighter. Its perfectly circular disk makes Vega unique — and confusing.
“The Vega disk is smooth, ridiculously smooth,” said Andras Gáspár of the University of Arizona and a research team member. “It’s a mysterious system because it’s unlike other circumstellar disks we’ve looked at.” Circumstellar disks are only found around young stars. Also known as protoplanetary discs, they contain the dust and debris that leads to planet formation.
Vega has been the object of many studies. In 1850, it became the first star other than the sun to be photographed and 22 years later it was the target for the first-ever spectrographic image. In 2021, researchers published compelling evidence of a “hot Neptune” exoplanet around Vega after a 10-year study, but this new research using the Webb Telescope up-ends that.
Vega: Rethinking How Planets Are Formed
Vega was the source of the alien signal in the movie Contact. It’s also the star that all other sky objects’ brightness is measured against; Vega’s magnitude — its apparent brightness in the night sky — is traditionally rated as zero.
However, the smoothness of Vega’s disk is confusing to astronomers because it means the make-up of its system is different from the solar system. “It’s making us rethink the range and variety among exoplanet systems,” said Kate Su of the University of Arizona, lead author of a paper presenting the Webb findings published in The Astrophysical Journal. Su was part of a team that in 2013 discovered what appeared to be a large asteroid belt around Vega, which hinted at the presence of planets.
Vega Vs. Fomalhaut
A similar star to Vega, called Fomalhaut — which is also 25 light-years distant, twice the mass of the sun and about 440 million years old — has three debris belts and likely plenty of planets. Planetary scientists can’t tell the difference between Vega and Fomalhaut.
“What’s puzzling is that the same physics is at work in both,” said Schuyler Wolff of the University of Arizona team, lead author of a paper presenting the Hubble findings published in The Astrophysical Journal. “Did the circumstellar environment, or the star itself, create that difference?”
Vega: How To See It Tonight
Vega in the constellation Lyra may be known as a summer star, but it’s easy to see right now. Look west shortly after dark, and you’ll see it shining high in the sky. It’s currently the lowest star in a famous asterism, the Summer Triangle, whose three corners are Deneb in Cygnus, bright Vega and Altair in Aquila. The Milky Way streams through it.
Vega is also a past and future “North Star.” Earth’s precession causes the pole stars to change; as it spins on its axis, a slight wobble causes that axis to trace out a 47° circle in the stars every 25,800 years.
For now, it points to Polaris. Vega was the “north star” in 12,000 B.C. and will be again around 13,700 A.D.
Wishing you clear skies and wide eyes.
