UNAB Researcher Leads Discovery of Possible Pairs of Rogue Planets in the Milky Way

Rogue planets, also known as interstellar planets, represent one of the least understood planetary populations in the Milky Way. Unlike planets in our solar system, they do not orbit a star, but instead move freely through the galaxy.

An international team led by Claudio Cáceres, researcher at the Institute of Astrophysics at Universidad Andrés Bello (UNAB) and the Center for Astrophysics and Associated Technologies (CATA), has discovered a population of binary rogue planets: systems of two planets that do not orbit a star and instead travel together through the Milky Way.

Regarding the discovery, Professor Cáceres, principal investigator of the study, said:

“This discovery opens up a series of fundamental questions about their origin, evolution, and physical characteristics. Studying these objects could provide important clues about how planetary systems form and what processes allow worlds without a host star to exist.”

Published in the prestigious journal Astronomy & Astrophysics, the study also included the participation of Matías Gómez, Director of the UNAB Institute of Astrophysics and researcher at CATA; Dante Minniti, researcher at the UNAB Institute of Astrophysics and CATA; Joyce Pullen, also from the Institute; Daniela Rojas, a doctoral candidate in Astrophysics; and Andrea Mejías, a graduate of the same doctoral program and now a researcher.

More Than a Decade Observing the Milky Way

The discovery was made possible through the analysis of data from the VVV/VVVX survey, led by Professor Dante Minniti and conducted using the VISTA telescope at ESO’s Paranal Observatory in Antofagasta.

“Our public ESO VVV/VVVX survey observed the sky for more than a decade, providing long-term, multi-epoch near-infrared imaging with exceptional photometric precision. These deep, high-resolution images allowed us to obtain highly accurate photometric and astrometric measurements,” explained Professor Minniti.

The team complemented this information with data from ESA’s Gaia mission, NASA’s WISE mission, and the Blanco Telescope at Cerro Tololo Inter-American Observatory in Coquimbo.

Using these datasets, the researchers identified more than one hundred rogue planet candidates, including nearly two dozen possible binary systems within the young Lower Centaurus–Crux stellar association.

Rogue Planets: Possible New Worlds?

“Discoveries like this allow us to explore an entirely new domain,” said Claudio Cáceres. “We are opening a window onto a population of worlds unlike anything found in our solar system.”

Beyond their rarity, these systems could have important implications for the search for habitable environments beyond traditional models. Scientists do not rule out the possibility that some of these planets could possess conditions favorable for habitability.

“If they experience tidal heating, a process already observed in moons orbiting giant gas planets in our solar system, these objects could retain internal heat even without a nearby star,” he explained.

“This could allow liquid water to exist, one of the key requirements for defining a planet as habitable, significantly expanding the range of habitability within the Milky Way,” added the researcher.

Next Steps in the Research

Dante Minniti highlighted the broader significance of the project:

“The power of the VVV/VVVX survey gives us the opportunity to substantially increase the number of rogue planets we know about, while opening an entirely unknown and unexplored realm: binary rogue planets.”

The team plans to continue the research through spectroscopic follow-up observations, which will help further characterize the physical properties of these objects and confirm their binary nature.

Among the possibilities under consideration are observations as part of the ESO Public Spectroscopic Survey VVVX-GalCen, led by Matías Gómez, Director of the UNAB Institute of Astrophysics.

“In the future, follow-up observations with ALMA, the James Webb Space Telescope (JWST), and the Extremely Large Telescope (ELT) would be highly desirable, as would observations with the Wide-Field Spectroscopic Telescope (WST), a new spectroscopic survey facility proposed for the next decade at ESO following completion of the ELT,” Minniti concluded.

This discovery positions the UNAB Institute of Astrophysics as a key contributor to the exploration of new frontiers in astronomy, contributing to a better understanding of the diversity of worlds in our galaxy.