The system is believed to be moving at a speed of at least 1.2 million miles per hour (1.93 million kilometers per hour), according to a NASA press release, making the exoplanet the first discovered planet orbiting a star that moves so fast. The team’s analysis was published in The Astronomical Journal.
The objects were first detected in 2011 after astronomers reviewed archival data from the Microlensing Observations in Astrophysics (MOA). The team that made this discovery considered that the objects were one of two possibilities: either a star larger than our Sun with a planet approximately 29 times the mass of Earth, or a planet about four times the size of Jupiter with a moon smaller than our planet. In either case, the larger object is about 2,300 times heavier than its partner.
To determine the system’s speed, the team calculated its transverse velocity, meaning the distance it has moved across the sky. Data from the Keck Observatory and the European Space Agency’s Gaia satellite indicate that the object is a star. However, the team plans to revisit it in a year to check whether it has moved in the correct direction and by the expected distance to match the 2011 signal.
“If high-resolution observations show that the star simply remains in the same position, then we can confidently say that it is not part of the system that caused the signal,” says Aparna Bhattacharya, co-author of the study, research scientist at NASA Goddard and the University of Maryland in College Park, in the same press release. “This would mean that the rogue planet and exomoon model is more likely.”
Given the system’s extraordinary speed, it could be a hypervelocity stellar system. Such a system may have reached its extreme speed due to interactions with the gravitational fields of other stars or objects, such as black holes, which have extremely strong gravitational fields.
Exoplanets are worlds that exist beyond our Solar System. They come in various shapes and sizes; some are so-called super-Earths—large rocky worlds similar to our planet. Others are super-Neptunes—gaseous worlds similar to Neptune but larger, or hot Jupiters—exoplanets similar in size to Jupiter but orbiting their star much closer than Jupiter does to the Sun, making them significantly hotter.
A few years ago, the Webb Telescope detected the atmosphere of an exoplanet in greater detail than ever before. In September last year, astronomers identified one of the most massive exoplanets ever found. The following month, five years of data from the European Southern Observatory’s Very Large Telescope confirmed that the closest star to the Sun has an exoplanet traveling through space alongside it.
Just last month, the first-ever supersonic winds were discovered sweeping across WASP-127b—a world slightly larger than Jupiter, discovered in 2016. Some of the most exotic exoplanets can be explored in NASA’s catalog, published in May 2024.
The Roman Space Telescope, set to launch in May 2027, is expected to uncover more of these mysterious worlds, along with numerous new discoveries in space.
“In this case, we used MOA with its wide field of view and then supplemented it with the Keck and Gaia telescopes for their sharper resolution. But thanks to Roman’s powerful field of view and planned survey strategy, we won’t need to rely on additional telescopes,” said Terry in the same press release. “Roman will do it all.”
For now, we can marvel at the absurd speed of this star and its planet—and wait for their identity to be confirmed, possibly as soon as next year.
