NASA Might Have Discovered the Fastest-Known Planetary System
Near the Milky Way’s central bulge, about 24,000 light-years from Earth, a peculiar pair of celestial objects is racing through space at unprecedented speeds.
Scientists believe this duo consists of a high-velocity star and its orbiting exoplanet, according to a new study. If confirmed, it would set a record as the fastest-known planetary system.
Stars constantly move across the Milky Way, typically at speeds of a few hundred thousand miles per hour. Our Solar System, for instance, travels through the galaxy’s Orion Arm at 450,000 miles per hour (200 kilometers per second). However, this newly identified pair moves at more than twice that speed, reaching at least 1.2 million miles per hour (540 kilometers per second).
“We think this is a super-Neptune world orbiting a low-mass star at a distance comparable to the space between Venus and Earth in our Solar System,” says astronomer Sean Terry from the University of Maryland and NASA’s Goddard Space Flight Center. “If that’s the case, it would be the first planet ever found orbiting a hypervelocity star.”
Researchers first detected these objects in 2011 while analyzing data from Microlensing Observations in Astrophysics (MOA), a project based at the University of Canterbury Mount John Observatory in New Zealand.
Gravitational Microlensing: A Powerful Tool for Detecting Hidden Celestial Bodies
The discovery relied on gravitational microlensing, a phenomenon where a massive object’s gravitational field bends and magnifies the light of a more distant star. This effect allows astronomers to detect celestial bodies that might otherwise remain invisible.
In 2011, scientists determined that one object was 2,300 times more massive than the other, but their exact masses remained uncertain.
“Determining the mass ratio is relatively simple,” explains astronomer David Bennett from the University of Maryland and NASA Goddard, who contributed to both the 2011 and 2025 studies. “The real challenge is calculating their actual masses.”
To establish mass, astronomers need to measure an object’s distance. Similar to adjusting a magnifying glass, shifting the perspective changes how the object appears without altering its relative proportions.
Back in 2011, researchers proposed two possible scenarios: either a Sun-like star with a planet 29 times Earth’s mass or a rogue super-Jupiter with a smaller moon.
Revisiting the Mystery: New Data Sheds Light on a High-Speed Star System
To resolve the mystery, scientists revisited the system using data from the Keck Observatory in Hawaii and the European Space Agency’s Gaia satellite. Their analysis pointed to a star system in the Milky Way’s densely packed central bulge—the galaxy’s equivalent of a bustling downtown compared to our Solar System’s quieter outskirts.
By comparing its current location to the 2011 signal, the team calculated the star’s velocity, confirming that it moves more than twice as fast as our Sun. However, this measurement only accounts for its motion across the sky. If the star is also moving toward or away from Earth, its true speed could be even higher.
At such extreme speeds, the star might exceed the Milky Way’s escape velocity, estimated between 550 and 600 kilometers per second. If so, it could eventually leave our galaxy and drift into intergalactic space—though not for millions of years, given the Milky Way’s vast size.
Despite the promising match between this system and the 2011 discovery, further confirmation is needed.
“To be certain the newly identified star is responsible for the 2011 signal, we need to observe it again in a year to check its movement,” Bennett explains. “If it remains stationary, then it’s likely not the culprit.”
In that case, an alternate theory—that the original signal came from a rogue planet with an exomoon—would gain support, says astrophysicist Aparna Bhattacharya from the University of Maryland and NASA Goddard.
Read Original Article: Science Alert
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