Now, current observations suggest there are hundreds of billions. Just a few decades ago, it wasn’t yet known if any exoplanets existed. The estimates for the total numbers of planets in our Milky Way – both bound to stars, and rogue – is staggering. If, as calculated, about a quarter of the Milky Way’s stars have lost one or more planets, as many as 50 billion planets should be rogue or free-floating, in our galaxy alone!īound exoplanets likely outnumber stars in the galaxy our single sun has eight major planets, and we’ve now seen thousands of planets orbiting single stars in multiple-planet systems. All of the Milky Way’s stars are thought to have originated in vast star-forming clouds like those in the Orion Nebula, and to have started life in star clusters much like the Trapezium star cluster. After all, the Trapezium star cluster is just one of thousands of known star clusters. The researchers then extrapolated those numbers to the rest of the galaxy, based on estimates of 200 billion stars in our galaxy. So 281 of 2,522 newly born planets would leave their original star-forming cluster altogether, to roam the space between stars and star clusters, according to this computer simulation. Image via NASA/ESA/Hubble Space Telescope.

It contains about 2,000 known stars, but there may be more as well. It is a young open cluster where the stars are all roughly the same age. The Trapezium star cluster is the bright area just left of center. View of the Orion Nebula – a well-known region of star formation – via the Hubble Space Telescope. Of these, 281 leave the cluster, others remain bound to the cluster as free-floating intra-cluster planets. Simon Portegies Zwart, an astronomer at the University of Leiden, recently told Bruce Dorminey of Forbes: The simulation included 2,522 planets orbiting 500 stars within the Trapezium cluster and showed that 357 of them would become free-floating planets within the first 11 million years of their evolution. They ran computer simulations of 1,500 stars in the Trapezium star cluster, a well-known region of star formation located some 1,300 light-years away in the Orion Nebula, in the direction of our constellation Orion. How did these astronomers’ research determine there might be 50 billion more? Only a dozen or so rogue planets have been discovered. These astronomers’ results were published on February 14, 2019, in the peer-reviewed journal Astronomy and Astrophysics.

But what about planets that don’t orbit stars? How many rogue, or free-floating planets wander the depths of space unbound? Some have already been found, and earlier this year astronomers at the University of Leiden in the Netherlands announced results of their new study, suggesting there are some 50 billion free-floating planets in our Milky Way galaxy. Help EarthSky keep going! Please donate what you can to our annual crowd-funding campaign.īased on findings from space- and ground-based telescopes in recent years, astronomers now estimate there are billions of exoplanets – planets orbiting distant stars – in our galaxy alone. Artist’s concept of rogue planet CFBDSIR J214947.2-040308.9.

Telescope glimpses freefloating