The Milky Way may have more rogue planets than stars

Hyperaxion Aug 23, 2020

According to scientists, NASA’s Nancy Grace Roman Space Telescope will reveal a myriad of rogue planets in the Milky Way.

A new study published in The Astronomical Journal suggests that there may be more rogue planets than stars in the Milky Way, and scientists hope NASA’s Nancy Grace Roman Space Telescope will help them find these lonely worlds.

The Milky Way may have more rogue planets than stars
An illustration of the Roman spacecraft. (Credit: NASA’s Goddard Space Flight Center)

“As our view of the universe has expanded, we’ve realized that our solar system may be unusual,” said Samson Johnson, a graduate student at Ohio State University in Columbus and one of the research authors. “Roman will help us learn more about how we fit in the cosmic scheme of things by studying rogue planets.”

Astronomers have always had a hard time finding planets that do not orbit stars. In the 1990s, they found planets outside the Solar System – exoplanets – for the first time, both gaseous and rocky, but most orbited stars.

The Roman telescope will look for rogue planets using a technique called gravitational microlensing. It is a method that analyzes how light bends due to the distortion of space-time by a massive object (as predicted by General relativity).

The research estimates that Roman is up to 10 times more sensitive to rogue planets than other telescopes and suggests that it could find objects of this type that have a mass equal to or greater than that of Mars.

Roman will focus on rogue planets in the Milky Way that are between the Sun and the center of our galaxy; a distance of about 24,000 light-years.

“There have been several rogue planets discovered, but to actually get a complete picture, our best bet is something like Roman,” Johnson said. “This is a totally new frontier.”

Stars in the Milky Way. (Credit: ESA / Hubble).

Some of these “hidden” planets in our galaxy are unlikely to be habitable. They do not orbit stars, so they must be extremely cold. However, studying them will broaden our understanding of how planets form.

“If we find a lot of low-mass rogue planets, we’ll know that as stars form planets, they’re probably ejecting a bunch of other stuff out into the galaxy. This helps us get a handle on the formation pathway of planets in general,” Johnson concluded.


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