Using advanced modeling, an international team of astronomers has identified the process that leads to the formation of rogue planets. The study suggests that they may be formed by violent interactions between circumstellar disks in young star clusters.
Rogue planets are peculiar space nomads, objects that drift freely in space and are not attached to any star. They include bodies with masses less than the minimum possible mass of a brown dwarf (13 Jupiter masses). They are often observed in young star clusters, such as the Trapezium Cluster in the Orion Nebula. Although the existence of rogue planets is well documented, their origin has long puzzled scientists.
Previous theories have suggested that rogue planets may be failed stars or planets ejected from their systems. The problem was that these models could not explain the large number of such objects, their pairs and synchronous motion with stars within the clusters. A new study, published in the journal Science Advance, suggests that they are formed by an entirely different process.
Using high-resolution hydrodynamic modeling, the researchers recreated the close encounters between two circumstellar disks — rotating rings of gas and dust surrounding young stars. When these disks collide at speeds of 2 to 3 km/s and distances of 300 to 400 a.u., gravitational interaction stretches and compresses the gas into elongated “tidal bridges.”
These tidal bridges then break up into dense filaments that further fragment into compact nuclei. On reaching a critical mass, they produce objects with a mass about ten times that of Jupiter.
The modeling also showed that up to 14% of such objects form double or triple systems with a distance of 7 – 15 a.u. between the components. Frequent disk collisions in dense environments such as the Trapezium Cluster can produce hundreds of rogue planets, which explains well their observed overabundance.
According to scientists, the discovery partly changes our ideas about cosmic diversity. Rogue planets may represent a third class of objects emerging not from the raw material of star-forming clouds or from planet-building processes, but rather from the gravitational chaos resulting from disk collisions.
According to Phys.org
