Astronomers may have found a star racing through our galaxy at an incredible speed—dragging a planet along with it!
If confirmed, this would be the fastest-moving exoplanet system ever discovered, traveling nearly twice as fast as our own solar system through the Milky Way.
The planetary system is estimated to be moving at 1.2 million miles per hour (540 km per second).
Scientists believe the planet is similar to a “super-Neptune,” meaning it’s bigger than Neptune but smaller than a gas giant like Jupiter.
This planet orbits a small, faint star at a distance that would place it between Earth and Venus if it were in our solar system. However, because the star is so weak, the planet is well outside its habitable zone, meaning it’s unlikely to support life.
“If this discovery is confirmed, it will be the first planet ever found orbiting a hypervelocity star,” said lead researcher Sean Terry from the University of Maryland and NASA’s Goddard Space Flight Center.
The team’s findings were published in The Astronomical Journal.
A star on the move
The journey to this discovery began in 2011 when scientists using the MOA (Microlensing Observations in Astrophysics) project spotted something unusual. MOA, a project based in New Zealand, looks for exoplanets by detecting how their gravity bends light from distant stars—a phenomenon called microlensing.
Microlensing occurs when a massive object, like a planet or star, passes in front of a more distant star. The gravity of the closer object bends and magnifies the light from the background star, revealing details about the objects in between.
In this case, scientists saw a microlensing signal that hinted at two objects: one about 2,300 times heavier than the other. However, they couldn’t tell whether the system contained a small star and a planet or a much larger rogue planet with a moon.
Tracking the mystery star
To solve this puzzle, astronomers turned to data from the Keck Observatory in Hawaii and ESA’s Gaia satellite. Their goal was to determine whether the system contained a visible star. If the pair were just a rogue planet and a moon, they would be invisible in the darkness of space. But if a faint star was present, they could track its motion.
Their search led them to a strong candidate about 24,000 light-years away, in the Milky Way’s galactic bulge—the crowded central region of the galaxy. By comparing its position in 2011 and 2021, the team measured its incredible speed.
Could it escape the galaxy?
So far, astronomers have only measured the star’s movement in two dimensions (side to side). However, if it’s also moving toward or away from us at high speed, its true velocity could be even greater.
If its speed surpasses 1.3 million miles per hour (600 km per second), the system could eventually escape the Milky Way and drift into intergalactic space. This would make it one of the rare known planetary systems on a journey beyond our galaxy.
To confirm whether the fast-moving star is the same object that created the microlensing signal in 2011, astronomers plan to track it again next year.
“If the star moves exactly as we predict, we’ll know it’s part of the system we detected in 2011,” said David Bennett, a senior research scientist at NASA Goddard. “If it stays put, then the rogue planet and exomoon explanation is more likely.”
Future observations with NASA’s upcoming Nancy Grace Roman Space Telescope could help answer these questions. Roman’s powerful instruments will allow astronomers to detect more fast-moving stars and planets, helping scientists understand how these systems are launched into high-speed orbits.
“In this case, we used multiple telescopes to piece together the story,” Terry said. “But Roman will have the ability to do all of this in one mission.”
This discovery is another reminder of how vast and dynamic our galaxy is, with stars and planets moving in ways we are only beginning to understand.
Source: NASA.
