Seventy rogue planets have recently been identified wandering the Milky Way.
Free-floating planets, also known as rogue planets, are planetary bodies that don’t revolve around a star. Published in Nature Astronomy at the end of December 2021, Núria Miret-Roig and colleagues at the University of Bordeaux and University of Vienna, Austria, presented evidence of the existence of at least 70 free-floating planets in our galaxy. Up until now, free-floating planets have been tricky to find and identify because of their proximity to stars (or lack thereof). However, this team sifted through two decades of data to discover these new free-floating planets.
Planets outside of our solar system have generally been identified using the star they orbit around. When observing a planet’s orbit through a telescope, there is always a point where the planet travels in front of its star, a phenomenon in astronomy known as a transit. The planet blocks light from the star, and researchers can gain a lot of information about the planet through measuring the star’s light, like its size or composition.
Since free-floating planets don’t orbit a star, astronomers can’t use this method to identify them. Instead, they take advantage of the fact that free-floating planets aren’t illuminated by stars. Even after their formation, these planets are still hot and can be detected by cameras on large telescopes. It was a complicated process of gathering data from across the electromagnetic spectrum and analyzing each tiny source. Still, it culminated in the worthwhile discovery of a large group of free-floating planets.
Found in the Scorpius and Ophiuchus constellations, a star-forming region near our sun, these free-floating planets have masses comparable to Jupiter. The exact number of these free-floating planets is still uncertain, however. Without accurate data on the planets' masses, perhaps these aren’t planets at all but are rather astronomical bodies 13 times more massive than Jupiter. Known as brown dwarfs these astronomical bodies are the result of failed stars, but they aren’t classified as planets.
A significant piece of this discovery was the availability of data from telescopes worldwide. Chris Davis, Program Officer at the National Science Foundation’s NOIRLab (Nighttime Optical and Infrared Lab), cited this study as an example of the need for accessible data. He stated that “this project illustrates the incredible importance of providing access to archival data from different telescopes, not just throughout the US, but worldwide.”
Miret-Roig was not sure what her team would find in the data but was thrilled at the number they uncovered, she said in a statement. In the same press release, project leader Hervé Bouy explained the data suggests the existence of many more free-floating planets. “There could be several billions of these free-floating giant planets roaming freely in the Milky Way without a host star,” he said.
The new data has implications about the origins of these planets. One theory is that they are formed via the collapse of a gas cloud that isn’t large enough to create a star, and another suggests they could have simply been kicked out of their solar system. Researchers want to use the Extremely Large Telescope (currently in construction in Chile) to gather more data about the free-floating planets already discovered, hopefully answering questions about how these rogue planets formed.
Source: Nature Astronomy, Eastern Southern Observatory, SciTech Daily, Space.com, The Independent