2023-10-03 12:42:56
Stars are usually born in groups (called binary systems). Lone exoplanets with Jupiter masses had been observed. Nobody expected Jupiterian exoplanets in binary systems that wander alone through the interstellar medium. The JWST telescope has observed them in the Trapezium Cluster located in the center of the Orion Nebula, in the constellation of Orion. 540 Jupiter-mass objects have been observed, among which there are 40 binary systems and 2 triple systems formed by Jupiter exoplanets separated by less than 1 arc second (390 AU, astronomical units). The name JuMBO has been coined (Jupiter-Mass Binary Objects) for these surprising binary systems formed by two bodies with masses between 3 and 7 Jupiter masses. None of the star system formation models, which predict the ejection of Jupiterian exoplanets, predict the ejection of JuMBOs. Perhaps we must look for new hypotheses for the formation and ejection of these binary systems.
The Trapezium Cluster has been observed through a mosaic of 700 images obtained with the NIRCam instrument at JWST. In this region, about 1,400 light years from Earth, thousands of young stars with masses between 0.1 and 40 times the mass of the Sun are observed; Many of them are surrounded by dense disks of gas and dust where exoplanets could be forming, although not all of them due to the intense ultraviolet radiation and strong winds of the most massive stars in the region. The big question now is how two or more Jupiter exoplanets can be ejected into one star system. Another question is whether double exoplanets, not only double Jupiters, but also double exo-Earths, exist in many planetary systems.
El artículo es Samuel G. Pearson, Mark J. McCaughrean, «Jupiter Mass Binary Objects in the Trapezium Cluster,» arXiv:2310.01231 [astro-ph.EP] (02 Oct 2023), doi: https://doi.org/10.48550/arXiv.2310.01231. . . . More disclosing information in Jonathan Amos, «James Webb telescope makes ‘JuMBO’ discovery of planet-like objects in Orion,» BBC, 02 Oct 2023.
The Orion Nebula is the most famous and best-studied H II region of the sky. A cradle for the formation of massive stars, across the entire spectral range, from very massive O types to M dwarfs, including substellar brown dwarfs and many planetary mass objects. Its innermost core, the Trapezium Cluster, is the region of highest density for these objects (up to 50 thousand stars per cubic parsec). For all these reasons, the Trapezium Cluster is the ideal laboratory to study the formation of stars and planets. Substellar objects below the mass limit for hydrogen consumption (0.075 M⊙, stellar masses) are called stellar mass objects (PMO); When they are young these objects are luminous and easy to detect, since they release gravitational energy as they contract; thus brown dwarfs experience periods of deuterium fusion. Substellar objects with masses below 13 Jupiter masses are called Jupiter planets (Jupiter’s mass is 0.00095 solar masses).
The Trapezium Cluster is home to a rich population of brown dwarfs and planetary mass objects (detecting objects with masses less than 3 Jupiter masses is currently bordering on impossible). The JWST telescope has been used to explore this region with its near-infrared camera (NIRCam): a total of 34.9 hours of observation between September 26 and October 2, 2022, divided into 12 filters: F115W, F140M, F162M , F182M, F187N, F212N, F277W, F300M, F335M, F360M, F444W and F470N. Jupiterines have effective temperatures between 890 and 2520 K, with peaks in their spectrum in the range between 1 and 3.3 µm. Thanks to the JWST filters, broad molecular absorption lines of H₂O, CH₄ and CO can be observed, confirming the planetary nature of these objects.
540 candidates for planetary mass objects have been identified in the Trapezium Cluster, with masses less than 13 Jupiter masses. The lowest mass candidate has 0.6 Jupiter masses, or 2 Saturnian masses. It is intended to obtain NIRSpec spectroscopy of many of these candidates in the future. Right now the information on its composition in H₂O, CH₄ and CO seems not very relevant to me (since it has great uncertainty, especially for lower mass exoplanets). The big surprise has been to find that 9% of the candidates are binary systems (this term is used for two or more bodies). According to theoretical models of the formation of planetary systems, this number would be expected to be negligible. JuMBOs are a surprise in exoplanetary physics.
In the first and second figures of this piece, five JuMBOs stand out in a small region of the Trapezium Cluster that have masses between 3 and 7 Jupiter masses, and, therefore, effective temperatures between 900 and 1200 K. The lines of absorption of H₂O and CH₄ in the NIRCam filters (future NIRSpec viewers will confirm this). Could they be spurious alignments in heaven? According to the authors, given the density of PMOs observed, it is expected that there are only about 3.1 spurious alignments among the more than 40 JuMBOs observed. Independent statistical studies will have to confirm these numbers.
JuMBOs have separations between ∼25 and 390 AU, which is considerably larger than the average separation in brown dwarf binary systems, which peaks at ∼4 AU. But since the method used can only detect separations greater than 25 AU, it cannot be ruled out that there is an additional population of JuMBOs with closer orbits. Furthermore, in JuMBOs the masses of Jupiterians tend to be very different from each other, when in brown dwarf binaries the masses are usually very similar to each other.
In short, we do not know how JuMBOs form and how they are ejected from the planetary systems of their stars. A better characterization of these systems is needed (thanks to NIRSpec spectra this will be achieved). In addition, new simulations of the formation of planetary systems are needed with an emphasis on finding the cause of the ejection of two gaseous planets simultaneously. Perhaps binary systems can form between planets, and double Earths exist around some stars, but future studies are needed to understand their formation. Without a doubt, a new surprise from the JWST that raises more questions than answers. Science is exciting.
#JWST #telescope #observes #JuMBOs #Jupitermass #binaries #Orion #Nebula