Astronomers discover newborn planet that formed in just 3 million years, challenging theories of planet formation
Astronomers have made a groundbreaking discovery in the field of exoplanet research, spotting a newborn planet orbiting a young star just 3 million years after its formation—an unusually rapid process in the cosmos. This planet, which is estimated to be 10 to 20 times the mass of Earth, is among the youngest exoplanets ever detected and challenges existing theories about the speed at which planets form.
The discovery was made by a team of researchers using NASA’s Transiting Exoplanet Survey Satellite (TESS). The planet, named IRAS 04125+2902 b or TIDYE-1b, resides in a protoplanetary disk—a dense cloud of gas and dust surrounding its host star. This disk, which provided the necessary ingredients for planet formation, is slowly dissipating as the star evolves.
The host star, located about 520 light-years from Earth in the Milky Way galaxy, is expected to become an orange dwarf, a star type that is cooler and less massive than our Sun. With a mass of about 70% of the Sun’s and only half its luminosity, the star offers a unique environment for planetary development. Despite its relative youth, the star’s system has already produced a planet that is much faster to form than previously thought possible.
“This discovery confirms that planets can form in just 3 million years, which was previously unclear, as Earth took 10 to 20 million years to form,” said Madyson Barber, a graduate student in physics and astronomy at the University of North Carolina at Chapel Hill, and lead author of the study published this week in Nature. “We’ve never seen such a young planet in this stage of formation before.”
The newfound planet orbits its star every 8.8 days, at a distance roughly one-fifth that of Mercury’s orbit around our Sun. Its mass is between that of Earth and Neptune, and though it is less dense than Earth, its diameter is about 11 times larger. Its chemical composition remains unknown.
The rapid formation of this planet raises questions about the process and timing of planetary growth. “We don’t really know how long it takes for planets to form,” said co-author Andrew Mann, an astrophysicist at UNC. “We know that giant planets must form faster than their disks dissipate, but how quickly can they form? Is it in 1 million years? 5 million? 10 million?”
The planet’s rapid development is particularly intriguing because it exists in a region of space where large planets are not typically thought to form quickly. The team suspects that the planet initially formed further from its star and migrated inward, as the inner regions of the protoplanetary disk dissipate the fastest, making it difficult for large planets to form close to the star.
“This planet’s formation challenges existing ideas about how planets form,” Barber said. “The protoplanetary disk near the star is supposed to dissipate too quickly for a planet of this size to form in such a short time. Yet, here we are.”
The discovery also sheds light on the methods used to detect exoplanets. The planet was identified through the “transit” method, which observes a dip in a star’s brightness as a planet passes in front of it from Earth’s perspective. This method is typically used for finding planets that orbit relatively close to their stars, like IRAS 04125+2902 b.
While other planets are sometimes detected through direct imaging, this method is usually reserved for much larger exoplanets, typically those around 10 times the mass of Jupiter. The fact that this particular planet is so young yet detectable marks a significant achievement for astronomers.
According to Barber, the outer regions of the protoplanetary disk around this young star appear to be warped, creating a “perfect window” for detecting the planet’s transit, an unexpected and fortunate discovery. “It was previously thought we wouldn’t be able to find a transiting planet this young because the disk would be in the way. But for reasons we don’t fully understand, the outer disk is warped, allowing us to spot the planet,” she explained.
This finding could reshape how astronomers think about planetary formation, offering new insights into the complexities of how planets emerge from the gas and dust surrounding young stars. The study not only provides a closer look at this particular planet but also opens the door to understanding how planets in other star systems might form faster than previously anticipated.
