Rogue planets, also known as free-floating planets (FFP) or isolated planetary-mass objects (iPMO), have become a major focus for astronomers.
The first such objects were detected in 2000 by teams at the United Kingdom Infrared Telescope (UKIRT) and the Keck Observatory, though earlier detections were made that were unconfirmed at the time.
Since then, research has shown that these planets may actually be more common than planets that orbit stars, with some estimates placing the population as high as 4 trillion in our galaxy alone.
As the name would suggest, these planets are unbound to any star system and likely were objects that were ejected from their system of origin, or formed on their own from dust and gas in the interstellar medium (ISM).
According to recent findings by an international team of astronomers, it appears this latter theory is correct.
Using the ESO’s Very Large Telescope (VLT), the team observed a rogue planet located approximately 620 light-years away in the constellation Chamaeleon that is still in the process of formation.
In addition, the rogue planet is many times the mass of Jupiter and continues to grow at a prodigious rate.
The team was led by Víctor Almendros-Abad, an astronomer at the Astronomical Observatory of Palermo and the National Institute for Astrophysics (INAF) in Italy.
Other members included researchers from the Institute of Astrophysics and Space Sciences at the University of Lisbon, the Dublin Institute for Advanced Studies, University College Dublin (UCD), the Mullard Space Science Laboratory, the European Southern Observatory (ESO), and multiple universities worldwide. Their findings were published on August 29th in the Astrophysical Journal Letters.
The study of rogue planets has advanced considerably, thanks to improvements in instruments and methods.
As a result, astronomers have a better understanding of how common these unbound bodies are and have learned some interesting things about them in the process.
Some research indicates that they may be capable of spawning their own planetary systems and that giant planets with exomoons could be capable of supporting life, similar to what scientists suspect from Europa, Enceladus, Titan, and other “Ocean Worlds” in the Solar System.
Between April and May, the team observed Cha 1107-7626 using the X-shooter spectrograph on the VLT.
This was combined with data obtained by the NIRSPec and MIRI instruments on the James Webb Space Telescope (JWST) and archival data from the VLT’s Spectrograph for INtegral Field Observations in the Near Infrared (SINFONI).
From this, the team determined that Cha 1107-7626 has a mass 5 to 10 times that of Jupiter and was still being fed by an accretion disk surrounding it.
However, their findings also indicated that the accretion process was not steady.
By August, their observations indicated that the planet was accreting approximately eight times faster than before, at a rate of six billion tonnes per second. This rate of accretion has never been observed with any rogue planets or any planets orbiting stars, for that matter. As Almendros-Abad indicated in an ESO press release:
People may think of planets as quiet and stable worlds, but with this discovery, we see that planetary-mass objects freely floating in space can be exciting places. This is the strongest accretion episode ever recorded for a planetary-mass object.
By comparing observations from before and during the burst, the team found that magnetic activity appeared to have played a role in driving the sudden infall of mass onto Cha 1107-762. Moreover, the spectra obtained from the disk also showed that its composition changed during the burst, with an increase in water vapor.
These findings suggest that low-mass objects may have magnetic fields strong enough to drive powerful accretion events, and that some rogue planets may follow a similar formation pathway to stars.
Whereas bursts of accretion and changes in a disk’s composition have both been seen with stars, they have never been observed with planets. These findings are not only unprecedented but may also shed light on the unresolved issue of how and where rogue planets originate.
“This discovery blurs the line between stars and planets and gives us a sneak peek into the earliest formation periods of rogue planets,” said co-author Belinda Damian, an astronomer at the University of St Andrews. As co-author and ESO astronomer Amelia Bayo puts it: “The idea that a planetary object can behave like a star is awe-inspiring and invites us to wonder what worlds beyond our own could be like during their nascent stages.”
While rogue planets are still very difficult to detect because of their faint nature, next-generation telescopes could lead to an explosion in discoveries – similar to what has happened with exoplanets.
These include the ESO’s Extremely Large Telescope (ELT), which is currently under construction in northern Chile, and the Nancy Grace Roman Space Telescope.
Using their high-resolution, adaptive optics, spectrometers, and coronographs, these observatories are expected to find several hundred to several thousand free-floating planets in the Milky Way.
Written by Matthew Williams/ Universe Today.
