400 Earth-size rogue planets could be wandering the Milky Way

[Judi Lynn]

By Robert Lea published 1 day ago

NASA's forthcoming Nancy Grace Roman Telescope will hunt for "cosmic orphans," starless planets that might even outnumber their orbiting counterparts in our galaxy.



An illustration of an ice covered rogue planet (Image credit: NASA’s Goddard Space Flight Center)

New predictions suggest an upcoming NASA space telescope could spot over 400 Earth-mass worlds hidden throughout the Milky Way that have "gone rogue" and therefore wander our galaxy alone.

Such orphan worlds are thought to start their lives in a planetary system, akin to the solar system, but get kicked at some point out by a mechanism thus far unknown. Despite the familiar picture of planets neatly orbiting a star, new research suggests such orphaned starless worlds may outnumber stars in the Milky Way by 20 to 1. This implies untethered worlds in our galaxy are around six times more common than planets orbiting parent stars.

"We estimate that our galaxy is home to 20 times more rogue planets than stars – trillions of worlds wandering alone," research author and NASA senior scientist, David Bennett, said in a statement. "This is the first measurement of the number of rogue planets in the galaxy that is sensitive to planets less massive than Earth."

Typically, planets outside our solar system, known as exoplanets, are detected by the effects they have on their host stars. For instance, an exoplanet can cause Earth-based viewers to witness a drop in its star's light as the planet's trajectory takes it between the star and our planet. Or, an exoplanet can affect such light through a wobble it creates in the orbit of its host star while gravitationally tugging on the glowing body. But the fact that rogue planets are so far away from host stars makes them tough to spot.

More:
https://www.space.com/400-earth-size-rogue-planets-could-be-wandering-the-milky-way