Direct imaging has revolutionized our view of the substellar population, revealing a growing population of free-floating planets. I will review the first discoveries, the current observational picture, and the prospects opened by upcoming instruments. I will describe the strategies used to identify free-floating planets, combining deep imaging, proper motions, and spectroscopy. Finally, I...
The origins of massive planets seen by direct imaging are uncertain, but these worlds far from their host stars are likely the most vulnerable to ejection in stellar encounters. We have just completed the Planet-Earth Building-Blocks Legacy e-MERLIN Survey (PEBBLeS), which gives the first view of the distribution of small rocks (planetary seeds) in the midplane of massive discs of young stars....
In a recent review paper, we have studied the pre- and proto-brown dwarf (proto-BD) population in different nearby clouds down to the planetary boundary (Palau+2024). Among our findings, we confirm that massive proto-BDs seem to follow the same trends as protostars in different star forming regions. On the other hand, we report an underproduction of low-mass proto-BD candidates in Ophiuchus...
We review the detection and mass-function measurements of free-floating planets (FFPs) or very wide-orbit planets using the microlensing technique. The microlensing surveys have identified several events with extremely short Einstein radius crossing times, t_E<0.5 days, and very small angular Einstein radii of theta_E <10μas. Such events are likely produced by low-mass lenses, potentially...
I will present an analysis of the microlensing event OGLE-2023-BLG-0524, the location of which was serendipitously captured in 1997 with the Hubble Space Telescope (HST). Our team conducted recent follow-up imaging with HST in 2025, thus we achieve a record-breaking baseline length of 28 years between the high-resolution epochs. The very short duration of this microlensing event (tE = 0.346 ±...
Free-floating planet (FFP) candidates detected via microlensing could also be bound planets on wide orbits (>5–10 au). High resolution imaging may break this degeneracy via direct detection of the putative host stars. We are conducting a multi-year Keck AO imaging survey of a large number of microlensing FFP candidates detected over the past two decades. I present preliminary results on phase...
Multiple studies show that planet–planet scattering plays a key role in the dynamical evolution of planetary systems. It can also contribute to the census of free-floating planets. In this work, we run an ensemble of N-body simulations and record the properties of ejected planets. Our simulations sample a wide range of orbital and physical parameters. We find that 40%–80% of planets are...
There is strong evidence from the broad eccentricity distribution of giant exoplanets that dynamical instabilities are ubiquitous. During the ejection of a planet, it may spend time on a wide enough orbit to be subject to external torques, from both passing stars (in particular, for early instabilities while the Sun was in its birth cluster) and the Galactic tidal field (for later dynamical...
The discovery of free-floating planets (FFPs) firmly confirms the fact that during the formation of a planetary system, fully-formed and still-forming planets are scattered out of the system. As planet formation is an inefficient process, meaning that the large majority of the material in a protoplanetary disk is scattered out and does not contribute to the growth of planetary bodies, question...
The role of massive stellar death in the production of free-floating planets remains poorly explored. We model type II supernovae as a rogue planet formation channel through 2.5 million simulations of planetary and stellar companions exposed to homologous mass loss with typical SN II ejecta velocities of 1000–10,000 km/s. Nearly all companions are destabilized, yielding rogue planets with...
Planets are known to ubiquitous around low-mass stars ($M \gtrsim 80$ $M_J$), and in our solar system, moons far outnumber the gas giant planets ($M \lesssim 1$ $M_J$) they orbit. But do rogue worlds, with masses in between our solar system planets and the lowest-mass stars, host orbiting bodies of their own? I will describe our team's work to observationally probe the population of small...
Rogue planets may retain moons after ejection from their host systems. The eccentric orbits of such moons can enable tidal heating sufficient for subsurface oceans to persist even without stellar irradiation. We test this through several thousand N-body simulations of planet–moon systems expelled by type II supernovae. All moons of rogue planets remain bound, with semi-major axes changing by...
While we expect moons outside of our Solar System to be common based on our own Solar System’s moon population and the predictions of satellite formation models, there have been no confirmed exomoon detections to date. JWST is collecting time-series observations of many free floating planets (FFPs) to study their weather, but these light curves are also the ideal datasets to search for...
Disc instability (DI) remains the leading formation pathway for some of the observed giant planets. In particular, this model can more naturally explain giant planets at large separation, giant planets around M stars, and very young giant planets. However, there are still many open questions regarding this formation mechanism, and the expected population of planets is currently unknown. We...
Abstract: Metallicity correlations and other observed statistics indicate that disc fragmentation due to Gravitational Instability (GI) is the likely origin of massive companions to stars, such as giant planets orbiting M-dwarf stars, Brown Dwarf (BD) companions to FGK stars, and binary stars with separations smaller than about 100 au. In paper I of this series, we showed that disc...
Over the past 25 years, observations have uncovered a large population of free-floating planets (FFPs), whose origins remain debated. Massive FFPs (several Jupiter masses or more) may form via gravitational collapse of molecular clouds, similar to stars. Lower-mass FFPs likely originate in planetary systems and are later ejected through dynamical interactions. We show that disc fragmentation...
Multiplanet systems are expected to form in resonance chains as a consequence of disk-driven migration. We investigate the dynamical evolution of cold Neptune systems initially assembled in resonance chains that later interact with planetesimals leftover from planet formation. We find that planetesimal masses comprising only 1–2% of the total planetary mass are sufficient not only to break the...
We have conducted an extremely deep spectroscopic survey of the NGC 1333 young star cluster using NIRISS on the JWST to identify and characterize the lowest-mass free-floating objects in its midst. Our observations cover 19 known brown dwarfs, for most of which we confirm previously assigned spectral types. We discover six new candidates with L-dwarf spectral types that are plausible...
A successful theory of star formation should predict the number of objects as a function of their mass produced through star-forming events. Previous studies in star-forming regions and the solar neighborhood have identified a mass function increasing from the hydrogen-burning limit down to about 10 MJ. Theory predicts a limit to the fragmentation process, providing a natural turnover in the...
Age-benchmark brown dwarfs' and planetary-mass objects' spectroscopy is key to characterize substellar evolution. In this paper we present the JHK medium resolution (R$\sim$3000) spectra of 25 7-76 $\mathrm{M_{Jup}}$ (spectral types L3.0-M6.0) brown dwarfs and planetary-mass objects in the Orion Nebula Cluster obtained with MOSFIRE installed at the W. M. Keck\,I telescope. We obtained the...
We present a new generation of ATMO2020 atmosphere models which is appropriate for application to studies low mass stars, brown dwarfs and rogue planetary-mass objects. The models compute temperature–pressure profiles and emergent spectra for atmospheres in both radiative–convective equilibrium and non-equilibrium chemistry, covering effective temperatures and surface gravities within the...
Starting with the Euclid Early Observations program and continuing with the Quick data release 1 and moving into the Data Release 1, our Independent Legacy Science team is focusing on the study of ultracool dwarfs in nearby star-forming regions, young open clusters and the field. Our first results showcase the power of Euclid to detect rogue planets directly via high spatial resolution...
Primarily designed to explore the dark universe, the Euclid space telescope also opens exciting new opportunities for substellar science. Its Early Release Observations and Quick Data Release include several young star-forming regions in Orion. In this talk, I will present results from Messier 78 (M78) and Lynds 1641 (LDN1641). The M78 data are representative of the Euclid Wide Survey, which...
Because it does not require the flux measurement of the lens, the microlensing technic is sensitive to a wide rage of dark range, from stellar mass black hole to the free-floating regime. Starting in 2027, it is expected that the Roman mission will detect thousands of free-floating planets. This will allow a first estimate of the population of these objects in the Milky Way. However, several...
The Euclid Galactic Bulge Survey (EGBS), conducted in late March 2025, will play a crucial role in maximizing the number of precise mass and distance measurements for Roman microlensing events. These observations can also be used to constrain the physical parameters of any microlensing event occurring within the survey fields.
An open question remains: can these data help us distinguish...
NASA’s Nancy Grace Roman Space Telescope — launching in late 2026 — will open up unprecedented discovery space in the infrared universe. Combining Hubble-like sensitivity and resolution with a field of view 100 times larger and a sky-mapping speed 1,000 times faster, Roman will conduct panoramic, high-resolution surveys that will transform our understanding of dark energy, exoplanetary...
The identification and modeling of rogue or wide orbit planets has been a challenging task for gravitational microlensing surveys, in part because of difficulties due to systematic errors and false positive detections. Roman will not have the same systematic errors and false positive signals as ground-based microlensing surveys, but the small number of magnified images and large expected rate...
Launching in less than a year, the Nancy Grace Roman Space Telescope is poised to detect hundreds to thousands of free-floating planets at masses ranging from that of Mars to beyond Jupiter. Reconstructing the mass distribution of these worlds would provide key insight into their origins and dynamical history, and as such, is a prime target for the Roman mission. However, due to the inherent...
JASMINE is an infrared space-based telescope mission being planned in Japan. The telescope is expected to orbit around the Earth and to observe microlensing events in parallax with other space-based telescopes located away from the Earth, such as Roman. As of now, the proposed JASMINE's target regime can support one of the Roman's observation fields close to the Galactic center, and...
One of the key questions about microlensing free-floating planet (FFP) events is whether the lenses are bona fide unbound or bound to a star that is not microlensing because of chance alignment. One avenue to verify boundness is to image the FFP events with high angular resolution in order to directly detect the putative host star. The highest resolution is obtained with interferometry. I will...
Circumstellar discs, a natural byproduct of the formation of low-mass stars and substellar objects, are crucial in setting the conditions and timescale for planet formation. These discs have been observed around free-floating planetary-mass objects (FFPMOs) at young ages. We present the near- and mid-infrared spectra of eight young FFPMOs with masses of 5–10 MJup, obtained using the NIRSpec...
A key step in the formation of planetary-mass objects (PMO's, objects <20 M_J) is the disc locking phase, where the object's rotation is regulated by magnetic coupling with its ionized circumplanetary disc. By dumping excess angular momentum into the disc and allowing further accretion, disc locking is responsible for setting both the rotation and mass distribution of PMO's. Due to decreasing...
Emission lines tracing active accretion have been detected in the youngest directly imaged exoplanets (e.g., PDS 70 b and c) and their free-floating counterparts. The profiles of these lines can provide valuable insights into the physics and kinematics of gas accretion, a process believed to determine the final spin of planetary-mass objects, their early physical evolution (hot- vs. cold-start...
The James Webb Space Telescope (JWST) has revealed that free-floating planetary-mass objects (FFPMOs) often host substantial dusty disks. A key unanswered question is whether these objects formed in isolation or were dynamically ejected from planetary systems. We test the ejection hypothesis with 3D hydrodynamical simulations of a giant planet, hosting a circumplanetary disk (CPD), ejected via...
The discovery of transiting planets with orbital periods exceeding 40 days has been exceptionally rare among the 5000+ planets identified to date. This dearth of findings poses a significant challenge to studying planetary demographics, formation, and evolution. In this study, we report detecting and characterizing HD88986 b, a potentially transiting sub-Neptune with the longest orbital period...
The Galaxy has an extremely large number of free-floating planets (ffps), either being bound in star clusters or orbiting freely around the Galaxy. The presence of these objects is common in all large scale objects, whatever we consider brown dwarfs as ffp or not. In my work, I will explain how these objects, with different abundances, remain gravitationally bound or are ejected from star...
Microlensing observations suggest that the mass distribution of free-floating planets (FFPs) follows a declining power-law with increasing mass. The origin of such distribution is unclear. Using apopulation synthesis framework, we investigate the formation channel and properties of FFPs, andcompare the predicted mass function with observations. Assuming FFPs originate from...
The traditional view of planet formation often treats planetary systems as isolated environments. However, dynamical processes are highly stochastic, and the "release" of material—from planetesimals to fully-formed planets—is a common, if not dominant, outcome. Planet-planet scattering, for instance, is a chaotic "release" mechanism that can eject 40-80% of a system's planets, populating the...
Cosmochemical studies have proposed that Earth accreted roughly 5%–10% of its mass from carbonaceous (CC) material, with a large fraction delivered late via its final impactor, Theia (the Moon-forming impactor). Here, we evaluate this idea using dynamical simulations of terrestrial planet formation, starting from a standard setup with a population of planetary embryos and planetesimals laid...
