Vega, one of the brightest and most famous stars in the night sky, has a slight wobble probably caused by a planet, scientists have discovered. If it's real it would be the second hottest planet yet discovered, a phenomenal addition to our collection of extreme worlds, and a ringside opportunity to study such staggering conditions.
Our methods for planet-finding make it much easier to detect worlds that are larger and closer to their star than others. Consequently, most of the first planets we found were so-called “hot Jupiters”, gas giants in orbits so close to their star they make household ovens seem chill. Nevertheless, we may have missed one of the hottest of hot Jupiters nearly under our nose.
Vega was the first star besides the Sun to be photographed. Given its fame and its relative closeness (25 light-years away), it's been an obvious target in planet searches. Carl Sagan even made it the source of the first extraterrestrial signal in his book Contact. However, attempts to find anything there have run into the obstacle that Vega is a fast-spinning and possibly variable star, which interferes with efforts to track its motion. Consequently, the wobbles caused by the gravitational tug of planets are particularly hard to detect amid the noise, although we have found signs of a debris disk far out from the star.
Nevertheless, some have continued trying, University of Colorado Boulder student Spencer Hurt among them. In The Astronomical Journal Hurt and colleagues have announced what appears to be a signal of a world operating at the edges of what is possible.
No transiting planets were found with TESS data (NASA'S planet-hunting survey), but by breaking down 10 years of data from the Fred Lawrence Whipple Observatory by spectral order, Hurt found Vega moving on a 2.4-day cycle. Even around a red dwarf, a planet with an orbit that short would be blisteringly hot. Vega, however, is 40 times as bright as the Sun, so the planet would have a temperature of 2,980 ºC (5,390 ºF), give or take a bit for atmospheric effects. That's actually slightly hotter than the nearest star to the Sun, Proxima Centauri.
The likely planet has a mass at least as large as Neptune, and possibly larger than Jupiter, depending on the alignment of its orbit with our view. Even if it's not confirmed, however, the authors don't think this is the end of the story for Vegan planets.
“This is a massive system, much larger than our own Solar System,” Hurt said in a statement. “There could be other planets throughout that system. It's just a matter of whether we can detect them.”
As Sagan noted, any advanced life around Vega would be visitors from elsewhere. It's such a young system that any life that may have evolved there would be just getting started, and the star's short life-span will prevent it from getting much further.
On the other hand, the closeness of Vegan planets would provide advantages to studying them, and anything learned about an extreme system could have implications elsewhere.
Vega is so bright it is visible even from the most light-polluted city, allowing everyone outside the southernmost parts of the planet to find it in the sky and feel part of the discovery. As Hurt put it, “Whenever I get to go outside and look at the night sky and see Vega I say, 'Hey, I know that star.'”