During a post-show Q&A the other day, we discussed how the only exoplanet stories we’re getting these days are about the wildest and weirdest planet discoveries. There’s a reason for that. We’ve found nearly 5,000 exoplanets, and the discoveries had gotten to the point where the press releases announcing them became so common that no one was really paying attention to them anymore. Once unusual and exciting, exoplanets are now pretty commonplace. Which has brought us to where the announcements are now about planets with strange orbits or unusual sizes, such as the ones that orbit in less than a day or are Mars-sized.

Today’s press release is no different in that regard. A new paper published in The Astrophysical Journal details the discovery of a massive exoplanet that could be a brown dwarf, orbiting at a huge distance from its star: over 1,600 astronomical units away. Remember, an astronomical unit is the average distance from the Earth to the Sun, so this giant of a planet is 1,600 times farther away. We haven’t found a lot of planets at that type of distance from their host stars.

Now, one of the coolest pieces of this story is that this particular exoplanet was discovered by a volunteer citizen scientist looking at data in the Backyard Worlds: Planet 9 project. Jörg Schümann noticed that a particular object was moving in tandem with a star. Other searches had missed the planet because of that huge distance between the planet and star. Lead author Jackie Faherty explains: This star had been looked at by more than one campaign searching for exoplanet companions. But previous teams looked really close to the star. Because citizen scientists really liked the project, they found an object that many of these direct imaging surveys would have loved to have found, but they didn’t look far enough away from its host.

This project is not one of those “look at light curves and flag dips” projects where we are dealing with exoplanet transits. Backyard Worlds uses data from NASA’s Wide-field Infrared Survey Explorer (WISE) mission, and citizen scientists look through digital images for objects that seem to jump between one image and another. Those objects are then flagged for further analysis.

So what do we know about this planet? It’s about ten to twenty times the mass of Jupiter. That’s kind of interesting considering the cutoff for becoming a brown dwarf is at about thirteen times the mass of Jupiter. This is either a really big gas giant or a brown dwarf. The main way we could tell the difference is if we knew how the object formed. Planets come from material gathering up in protoplanetary disks of dust and gas. Brown dwarfs form like stars, by a collapse of a giant cloud of gas. But we don’t have enough data to conclude, either way, so let’s just say there is a really big world out there.

More Information

AMNH press release

“A Wide Planetary Mass Companion Discovered through the Citizen Science Project Backyard Worlds: Planet 9,” Jacqueline K. Faherty et al., 2021 December 9, The Astrophysical Journal