Scientists discover a ‘rogue’ planet cruising through the Milky Way

An elusive, Earth-sized planet is creeping through our galaxy.

Scientists have long theorized about roving planets, which travel across galaxies and have no star to orbit. Untethered to their own sun, free-floating planets do not radiate light the way orbital planets do, meaning traditional research models couldn’t prove their existence.

Now, these cosmic rolling stones are no longer complete unknowns.

It was just a few years ago that Polish astronomers could provide the first evidence of such nomadic planets in our own Milky Way, using relatively new methods of detection. Now, the same team of OGLE (Optical Gravitational Lensing Experiment) researchers has announced the smallest planet yet ever discovered through their evolved methods — and it could be just one of many in our galaxy.

Previous techniques relied on patterns of dimming light to find new planets, which make the star appear to flicker as the world passes between the viewer and its star.

Since free-floating planets have no star — and thus little detectable radiation, astronomers at the Astronomical Observatory of the University of Warsaw were able to observe these planets through a phenomenon called “gravitational microlensing,” which behaves something like a magnifying glass. Bended light emitted from a star in the foreground demonstrates a gravitational warping, which they deem to be caused by a planet, just passing through the frame.

It can also be seen through ground-based telescopes. Trouble is, the method is finicky.

“Chances of observing microlensing are extremely slim because three objects — source, lens and observer — must be nearly perfectly aligned. If we observed only one source star, we would have to wait almost a million years to see the source being microlensed,” said Przemek Mróz, who co-authored a new study on the findings, published in Astrophysical Journal Letters.

The newly discovered planet, found in a central area of the Milky Way known as the Galactic Bulge, is the smallest rogue planet ever noted, with an estimated mass somewhere between that of Earth’s and Mars’.

In a statement, researchers said it’s further proof that “ground-based” telescopes could be used in the search for wayward exoplanets — a study for which NASA has devoted their new Nancy Grace Roman Space Telescope. Set to launch in 2025, the telescope will “investigate long-standing astronomical mysteries, such as the force behind the universe’s expansion, and search for distant planets beyond our solar system,” according to NASA.

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