NASA Searching for Free-Floating Planets With Artificial Intelligence and Gravitational Microlensing

Jupiter-Like Rogue Planet

This illustration shows a Jupiter-like planet alone in the dark of space, floating freely without a parent star. CLEoPATRA mission scientists hope to improve the mass estimates of such planets discovered through microlensing. Credit: NASA’s Goddard Space Flight Center Conceptual Image Lab

Exoplanet hunters have found thousands of planets, most orbiting close to their host stars, but relatively few alien worlds have been detected that float freely through the galaxy as so-called rogue planets, not bound to any star. Many astronomers believe that these planets are more common than we know, but that our planet-finding techniques haven’t been up to the task of locating them.

Most exoplanets discovered to date were found because they produce slight dips in the observed light of their host stars as they pass across the star’s disk from our viewpoint. These events are called transits.


This animation illustrates the concept of gravitational microlensing with a rogue planet — a planet that does not orbit a star. When the rogue planet appears to pass nearly in front of a background source star, the light rays of the source star become bent due to the warped space-time around the foreground planet. Credit: NASA’s Goddard Space Flight Center/CI Lab

Goddard scientist Dr. Richard K. Barry is developing a mission concept called the Contemporaneous LEnsing Parallax and Autonomous TRansient Assay (CLEoPATRA) to exploit parallax effects to calculate these distances. Parallax is the apparent shift in the position of a foreground object as seen by observers in slightly different locations. Our brains exploit the slightly different views of our eyes so we can see depth as well. Astronomers in the 19th century first established the distances to nearby stars using the same effect, measuring how their positions shifted relative to background stars in photographs taken when Earth was on opposite sides of its orbit.

It works a little differently with microlensing, where the apparent alignment of the planet and distant background star greatly depends on the observer’s position. In this case, two well-separated observers, each equipped with a precise clock, would witness the same microlensing event at slightly different times. The time delay between the two detections allows scientists to determine the planet’s distance.

To maximize the parallax effect, CLEoPATRA would hitch a ride on a

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