The field of extrasolar planet studies continues to reveal amazing things about our Universe. After decades of having just a few exoplanets available for study, astronomy is now working with a total of 4,884 confirmed exoplanets and another 8,288 awaiting confirmation. The number is expected to increase as more and more missions are launched.
Astronomers have learned a lot about the types of exoplanets that are out there and what kind of stars are known to give rise to them, but they have also made another startling discovery. There are many exoplanets that don't have a parent star. A team of astronomer discovered 70 additional free-floating planets, the largest sample of "Rogue Planets" to date, and nearly doubled the number of FFPs available for study.
Nuria Miret- Roig is a researcher with the University of Vienna and the Laboratoire d'Astrophysique de Bordeaux. She was joined by researchers from the National Institute of Natural Sciences in Kyoto, the Centre National de la Recherche Scientifique in France, and the Centro de Astrobiologa. The study describes their findings.
Astronomers have speculated about the existence of FFPs for decades, and numerical simulations have indicated that they may be common. Billions of these planets may be floating around in space, potentially outnumbering stars in the Milky Way! There are many theories about how planets go rogue.
Astronomers theorize that planets are pulled away from the stars by interactions with passing stars, that they are kicked out by supernovae, or that they float into space after their sun dies. Roig and her colleagues stated that previous research has identified FFPs in young stellar clusters. The samples were always small and heterogeneous.
It is difficult to image rogue planets in visible light, like trying to discern exoplanets that are several thousand times brighter. Astronomers need access to telescopes and instruments. They need to identify planetary-mass members within a large number of field stars and background galaxies. This is similar to finding a needle in a haystack, but with the least-shiny object.
Roig and her team combined the motions of objects in the night sky with multi-wavelength photometry obtained by multiple observatories over 20 years to overcome this. The Canada-France-Hawaii Telescope, the VLT, and the VISTA were included.
The locations of 115 potential rogue planets, highlighted with red circles, were recently discovered by a team of astronomer. The credit goes to N.Risinger.
The European Space Agency has a space-based observatory. The project leader of the new research is Hervé Bouy.
The majority of our data comes from the observatory. Their sensitivity and wide field of view were keys to our success. We used tens of thousands of wide-field images from the facilities of the European Organization for Astronomy.
The team took advantage of how younger rogue planets are still warm from formation, allowing them to be detected by telescopes and cameras. The team was able to get over 80,000 wide-field images (100 terabytes of data) thanks to the new deep wide-field observations. The team found at least 70% of the new FFPs in the Scorpius and Ophiuchus constellations, which are the closest star-forming regions to our Solar System.
This was the largest sample of FFPs ever discovered, as stated in a recent press release.
We didn't know how many to expect, but we are excited to have found so many. We measured the motions of the stars in a large area of the sky. The faintest objects in this region are the rogue planets.
Astronomers will have nearly twice the data set they previously had, which will come in handy when follow-up observations happen in the near future. Astronomers are using this large sample to refine their theories about the nature and origin of rogue planets. The number of FFPs observed in the Upper Scorpius association exceeds what would be expected if they only formed as stars.
This suggests that there could be many more mechanisms at play and that previous estimates that suggested there could be billions of FFPs in our galaxies are correct. If the fraction of FFPs that they observed in Upper Scorpius is similar to other star-forming regions, there would be several billion Jupiter-mass planets roaming the galaxy and even more Earth-mass planets.
There could be billions of giant planets in the sky without a host star. These objects are very faint and can't be studied with current facilities. The ELT will be crucial in gathering more information about the planets.
The first light from the ELT is expected to be visible by 2027. The ELT will be able to image exoplanets, rogue planets, and their atmospheres with its 39-meter primary mirror and advanced suite of spectrometers, coronographs, and adaptive optics. NASA will launch the Nancy Grace Roman Space Telescope in the same year, and begin conducting exoplanet surveys that could include FFPs as small as Mars.
Excellent targets for follow-up studies were identified by the FFPs we identified. They will be essential to study planetary atmospheres in the absence of a blinding host star, making the observation far easier and more detailed. Key details about their formation and properties will be provided by the comparison with atmospheres of planets. The presence of gas and dust around these objects will shed more light on their formation process.
This study has implications for models of planet formation and evolution, which are important to understanding the origin of life on planets. Said Miret- Roig.
The discovery of a large population of young FFPs has important implications for the formation and early evolution of planetary systems. Our observations show that giant-planet systems must form and become unstable within the lifetime of the region to contribute to the population of FFPs. The instability of giant planets in our Solar System may have occurred at an earlier time than we have found, although it was less violent than the instability needed to ejected planets as massive as the ones we have found.
There is a chance that FFPs could host life, possibly tucked away in subterranean pockets where the slow decay of radioactive elements or convection provides the necessary heat. There is a chance that FFPs could have moons with thick atmospheres and water on their surface, which would raise the possibility of life again. Is any of these possibilities real? We will find out one way or another with hundreds or thousands of FFPs available for study.
Nature Astronomy and the IsaacNewton Group are further reading.
