A tiny star is making big moves — whether its accomplice likes it or not.
Astronomers have spotted a star just a fraction the mass of the Sun crashing through the Milky Way at an unbelievable pace. And astonishingly, it’s managed to drag its exoplanet along, as the poor world hangs on for dear life.
As detailed in a new study published in The Astronomical Journal, the host star is absolutely hauling it at at least 1.2 million miles per hour, making it the fastest-moving exoplanet system discovered to date, according to NASA.
“We think this is a so-called super-Neptune world orbiting a low-mass star at a distance that would lie between the orbits of Venus and Earth if it were in our solar system,” study lead author Sean Terry, a researcher at NASA’s Goddard Space Flight Center, said in a NASA statement. “If so, it will be the first planet ever found orbiting a hypervelocity star.”
Of course, speed is relative. To us, the Sun is stationary. But with reference to the Milky Way, our solar system is orbiting around the galactic center at an average velocity of 450,000 miles per hour. And the Earth, relative to the Sun, moves at around 67,000 miles per hour.
Our perspective of the hyperspeed star, then, may be a little skewed. In reality, it could be traveling much faster than it appears, if it’s moving towards or away from our planet. That opens the possibility that the star is actually whipping around at 1.3 million miles per hour — fast enough to break free from the Milky Way, making it a potential “rogue star” doomed to roam the intergalactic void.
Spotting the star and its exoplanet is a remarkable discovery. Because they have no luminosity of their own, exoplanets are often outshined by stars, if not entirely lost to the lightless realm of space.
Both objects were first spotted back in 2011 using microlensing, a technique that searches for distortions of light caused by the gravity of nearby objects. If the conditions are right, even the mass of just a star or a planet could be enough to bend light like a natural lens, providing a better view of what lies behind it.
At the time, the findings were enough to determine the mass ratio between the two objects, with one being 2,300 times heavier than the other. But there wasn’t enough data to rule out the possibility that the pair comprised a rogue planet — that is, one that’s broken from from its star system — four times the mass of Jupiter, and its moon.
But when looking at data collected in 2021, astronomers found a candidate system that strongly resembled the one detected a decade ago, located in a star-dense region of the Milky Way roughly 24,000 light years away. The fact that they could even see it in the first place strongly suggests that they’re on the trail of an escaping tiny star, not a huge planet.
As promising as the findings are so far, there’s still some additional detective work needed to put this case to bed.
“To be certain the newly identified star is part of the system that caused the 2011 signal, we’d like to look again in another year and see if it moves the right amount and in the right direction to confirm it came from the point where we detected the signal,” coauthor David Bennett, a senior research scientist at NASA Goddard, said in the statement.
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