the Astrophysical Journal Letters A study recently published in the journal Science explores the possibility of Mars-sized free-floating planets (FFPs), also known as stray planets, that may have been captured by our Sun's gravity and orbited in the outer solar system at a distance of about 1,400 AU. (AU) from the sun.
In comparison, the farthest known object in the solar system is Pluto, which orbits about 39 AU from the Sun and is also part of the Kuiper Belt. However, scientists estimate that the area is up to 1,000 astronomical units.
Current scientists estimate that billions, if not trillions, of FFPs may exist in our Milky Way Galaxy. A recently presented study using data from NASA's James Webb Space Telescope (JWST) identified 540 possible Jupiter-sized planets, some of which are thought to be planetary pairs.
This was followed by another recent study that also looked into the origin and formation of rogue binary planets. Scientists currently assume that there are two scenarios for rogue planet formation. Either as part of their solar system, and later expelled into the universe somehow, or they form in isolation. But why is this important when studying free planets?
Can there be many planets in the solar system?
“We can identify three interesting areas in astrophysics with free planets,” said Amir Siraj, a doctoral student in astrophysics at Princeton University and the study's sole author. For the universe today. “The first is the formation of planetary systems. Free-floating planets appear to be a byproduct of the planetary system formation process, so they can help shed light on how planetary systems like ours came to be.”
“The second is habitability. The number of free planets may exceed the number of planets associated with star systems, so if a portion of any of them has the appropriate energy balance to sustain liquid water, then free planets together may represent a significant portion of the habitable worlds in the universe.”
“The third is dynamic interaction with stars and planetary systems. Since free planets are not bound to any star, they drift through the galaxy and can dynamically interact with many different stars and planetary systems.”
Siraj also said he used this third field of study when he asked how likely our solar system was to capture FFPs during its roughly 4.5 billion-year history.
For the study, Siraj used computer models to simulate the possibility of capturing FFPs in the outer solar system, taking into account a myriad of factors, including the semimajor axis, eccentricity, and observation time of the FFPs. After about 100 million simulations, the results showed that somewhere in the outer solar system, at a distance of about 1,400 astronomical units from the Sun, there might exist an object the size of Mars or even Mercury. Siraj indicates in his paper that the distance could range between 600 and 3,500 astronomical units. But what is the significance of the presence of a terrestrial planet so far in the outer solar system versus a gas giant planet?
“Because this planet is a former exoplanet, studying it in detail will reveal a wealth of information about how planets form around other stars. The fact that it is a terrestrial planet means that its surface is likely to be rocky. Which is very exciting, because it means that by studying On its surface, we will generally learn more about the habitability of such Earth-like exoplanets.
Siraj recommends in his paper that future work includes better understanding how stray planets are captured in the first place, and examining observational tests to determine where to look for these planets in the sky. He also points out that microlensing has become the preferred method for identifying rogue planets based on previous studies.