NASA’s Kepler space telescope has found a mysterious group of “freely floating” or “rogue” planets that are not associated with any host star.
Based on a technique called gravitational microlensing, the researchers revealed four new rogue planets in the group, which likely have masses similar to Earth’s.

The micro-gravitational lensing is based on chance events where one star from a certain point of view passes in front of another star.

Experts say the planets may have originally formed around a host star before being pushed out by the gravitational pull of other, heavier planets in the system.

It is possible that the host star is still burning brightly in space, but with fewer planets in its orbit.

Study author Professor Ian MacDonald, from the University of Manchester, said: “We don’t know exactly how far away it is. It could be said to be several thousand light-years away. If a planet like Earth shot out into deep space, away from the heat of a star, we would expect the oceans to freeze and the atmosphere to condense. “Life can still go on, but only in places like hydrothermal vents, where there is another source of energy.”
The now retired Kepler telescope has spent nearly a decade in space searching for Earth-sized planets orbiting other stars, but scientists are still analyzing its data.

Kepler was launched in 2009, only to be decommissioned by NASA in 2018 when it ran out of fuel for further science operations.

The researchers used data obtained in 2016 during the K2 mission phase of NASA’s Kepler Space Telescope – an extension of its original mission.

During the two-month K2 mission, Kepler monitored a crowded field of millions of stars near the center of our galaxy every 30 minutes in order to find rare microgravity events.

The study team found 27 short-lived filter microlens signals that vary over timescales ranging from an hour to 10 days.

Confirming the existence and nature of free-floating planets will be a major focus of NASA’s upcoming Roman “Nancy Grace” space telescope, and possibly the European Space Agency’s Euclid mission.

Study author Eamonn Kearns, from the University of Manchester, said: “Kepler has achieved what it was never designed to do, by providing more tentative evidence for the existence of a group of Earth-mass floating planets.”

The results were published in the Monthly Notices of the Royal Astronomical Society.