NASA explains untethered Earth-size planets are wandering the Milky Way alone

New research from scientists from NASA and Japan's Osaka University has explored the idea that there are rogue planets wandering interstellar space waiting to be discovered by lucky astronomers.

The study, which NASA writes is expected to appear in a future issue of The Astronomical Journal, used data from a near-year survey conducted at the Mount John University Observatory in New Zealand. According to a NASA press release, the team estimates that there are 20 times more rogue planets than stars within the Milky Way galaxy. Rogue planets are worlds that aren't gravitationally tethered to a local star, and are just wandering through interstellar space completely alone.

Using microlensing techniques, which is the process of observing stars for any change in brightness levels. If an object passes directly between the star and the observer's line of sit, the gravity of that object warps space-time and creates a natural lens. This lens briefly amplifies the brightness of the star, giving a clue to astronomers about the nature of the intersecting object.

Since these rogue planets aren't tethered to any star, they are hardly exposed to any light, making them almost undetectable. However, NASA has a project up its sleeve that's designed to identify rogue planets that have a mass similar to Earth's.

"NASA's Nancy Grace Roman Space Telescope, set to launch by May 2027, could find a staggering 400 Earth-mass rogue worlds," writes NASA

"Roman will be sensitive to even lower-mass rogue planets since it will observe from space," said Naoki Koshimoto, who led the paper announcing the detection of a candidate terrestrial-mass rogue world, a assistant professor at Osaka University. "The combination of Roman's wide view and sharp vision will allow us to study the objects it finds in more detail than we can do using only ground-based telescopes, which is a thrilling prospect."