Astronomers have discovered evidence for a giant planet orbiting Vega, a young star located 25 light-years away in the constellation of Lyra.
An artist’s impression of a massive planet around Vega. Image credit: Fossart / CC BY-SA 4.0.
“Scientists can also see Vega with telescopes even when it’s light out, which makes it a prime candidate for research,” said Dr. Samuel Quinn, an astronomer at the Harvard and Smithsonian Center for Astrophysics.
“It’s bright enough that you can observe it at twilight when other stars are getting washed out by sunlight.”
“It would be really exciting to find a planet around Vega because it offers possibilities for future characterization in ways that planets around fainter stars wouldn’t,” he added.
Vega is an A-type star, the name for stars that tend to be bigger, younger and much faster-spinning than the Sun.
Also known as Alpha Lyra, Gliese 721 and HD 172167, the star is 455 million years old, and has a mass of two solar masses.
It rotates around its axis once every 16 hours — much faster than the Sun with a rotational period that clocks in at 27 Earth days.
“Such a lightning-fast pace can make it difficult for scientists to collect precise data on the star’s motion and, by extension, any planets in orbit around it,” Dr. Quinn said.
In the study, Dr. Quinn and colleagues analyzed 1,524 spectra of Vega collected by the Fred Lawrence Whipple Observatory during 10 years.
They detected a candidate radial-velocity signal with a period of 2.43 days.
If caused by an orbiting planet, its minimum mass would be 20 Earth masses. Because of Vega’s pole-on orientation, this would correspond to a Jovian planet if the orbit is aligned with the stellar spin.
“It would be at least the size of Neptune, potentially as big as Jupiter and would be closer to Vega than Mercury is to the Sun,” said Spencer Hurt, an undergraduate student in the Department of Astrophysical and Planetary Sciences at the University of Colorado Boulder.
“That close to Vega the candidate world might puff up like a balloon, and even iron would melt into gas in its atmosphere.”
The candidate planet, Vega b, could also rank as the second hottest world known to science — with surface temperatures averaging a searing 2,980 degrees Celsius (5,390 degrees Fahrenheit).
“This is a massive system, much larger than our own Solar System,” Hurt said.
“There could be other planets throughout that system. It’s just a matter of whether we can detect them.”
The results were published in the Astronomical Journal.
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Spencer A. Hurt et al. 2021. A Decade of Radial-velocity Monitoring of Vega and New Limits on the Presence of Planets. AJ 161, 157; doi: 10.3847/1538-3881/abdec8
