Sizzling Planet Might Orbit Star Vega

by AMNH on

Research posts

Star shines brightly in space. Vega, the brightest star in the Lyra constellation.
Courtesy of S. Rahn/Wikimedia Commons

The bright star Vega, which is just 25 light years—or about 150 trillion miles—from Earth might be best known in popular culture as the origin of an extraterrestrial message in the book and Hollywood film Contact.

Researchers have yet to find a single planet in orbit around Vega, but that might be about to change: Drawing on a decade of observations from the ground, a team of scientists led by the University of Colorado Boulder and including Museum Assistant Curator Ruth Angus, unearthed a signal that could be the star's first-known world.

Rendering of Vega shining brightly with planet KELT-9b below it.
Artist's depiction of a planet named KELT-9b, currently the hottest known exoplanet, which may resemble a candidate world in orbit around Vega.
Courtesy of NASA/JPL-Caltech

“Aside from the Sun, Vega is perhaps the most significant star to many astronomers. It’s the fifth-brightest star in the night sky—it’s so bright that the brightnesses of other stars are measured against it,” Angus said. “Vega was the first star ever to be photographed and the first to have its spectrum measured, a spectrum is the intensity of light emitted over a range of colors. It is fitting therefore that that very spectrum, now monitored over the last 10 years, has revealed the presence of a world orbiting Vega almost 150 years after it was first photographed.”

Vega, which is part of the constellation Lyra, is what’s called an “A-type” star, which describes stars that tend to be bigger, younger, and much faster-spinning than our own Sun. Vega rotates around its axis once every 16 hours—much faster than the Sun—which can make it difficult for scientists to collect precise data on the star’s motion and any planets that orbit it.

For this study, published this month in The Astronomical Journal, the researchers pored through roughly 10 years of data on Vega collected by the Fred Lawrence Whipple Observatory in Arizona, looking for a tell-tale signal of an alien planet: a slight jiggle in the star’s velocity.

“If you have a planet around a star, it can tug on the star, causing it to wobble back and forth,” study coauthor Samuel Quinn, an astronomer at the Harvard and Smithsonian Center for Astrophysics. The team discovered a signal that indicates that Vega might host what astronomers call a “hot Neptune,” a type of giant planet with a mass similar to Uranus or Neptune orbiting close to its star, or maybe a “hot Jupiter," a class of gas giant planets that are inferred to be physically similar to Jupiter but that have very short orbital periods.

“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 University of Colorado Boulder student Spencer Hurt, the lead author of the study.

If the team's findings bear out, the planet would orbit so close to Vega that its years would last less than two-and-a-half Earth days. (Mercury, in contrast, takes 88 days to circle the sun). This candidate planet could also rank as the second hottest world known to science—with surface temperatures averaging a searing 5,390° Fahrenheit (2,977° Celsius).

The research also helps narrow down where other, exotic worlds might be hiding in Vega’s neighborhood. But a great deal of work remains before the scientists can definitively say that they've discovered this sizzling planet. A next step could be to scan the Vega star system directly to look for light emitted from the hot, bright planet.