Traditionally, it was believed that planets must orbit around a specific star, but astronomers have now uncovered the existence of “homeless” planets that can wander freely throughout the universe.
In a study published in the Monthly Notices of the Royal Astronomical Society, scientists utilized data from NASA’s Kepler space telescope during a two-month period in 2016, known as the K2 mission, to identify these wandering planets.
Description of a Free-Floating Planet in Space. Image: University of Manchester
Lead researcher Eamonn Kerins from the University of Manchester stated, “Kepler achieved something it was never designed for, by providing further evidence of the existence of Earth-mass planets, free-floating in space.”
During this two-month timeframe, Kepler observed millions of stars near the center of our galaxy every 30 minutes. Through data analysis, researchers hoped to detect rare events called gravitational microlensing. This phenomenon occurs when an object passes in front of a background star, and its gravitational field bends the star’s light, causing it to appear brighter for a certain period of time. This acts as a cosmic magnifying lens, enabling scientists to detect objects that would otherwise be too distant to observe.
Through their research, scientists discovered 27 candidate signals of varying durations, ranging from one hour to 10 days. Among these, four brief gravitational microlensing events matched the presence of Earth-sized planets without a host star or a star with planets in orbit. This implies that these planets are free-floating in space.
It is also suggested that these “free-floating” planets may have initially formed around a host star and were subsequently ejected by the gravitational interaction with larger planets or objects.
However, the scientists emphasize that detecting signals from these free-floating planets is a challenging task, especially considering that Kepler was not designed to detect planets through gravitational microlensing events, and its mission ended in November 2018 after nearly a decade of space operation.
Lead author Ian McDonald, a researcher at the University of Manchester, stated, “These signals are incredibly difficult to find… It’s like searching for the faint glimmer of a firefly in the middle of a motorway, using only a handheld phone.”
To achieve this, the research team had to develop new techniques for data analysis. They believe that future observations using NASA’s Nancy Grace Roman Space Telescope and possibly the Euclid mission, focused on dark matter and dark energy search by the European Space Agency (ESA), could help detect signals from gravitational microlensing events and further confirm the existence of these peculiar wandering planets.