An international collaboration of astronomers has identified a unique planetary configuration that challenges current models of the formation of celestial bodies. The focus of the study is the star LHS 1903, a red dwarf located about 116 light-years from Terra, which hosts a system made up of four planets. The peculiarity lies in the arrangement of these worlds: an inner rocky planet, followed by two gaseous ones and, surprisingly, a fourth rocky planet in the outermost orbit. Essa architecture contradicts the pattern observed in Sistema Solar and in most known systems, where gas giants tend to occupy the most distant regions.

The research, which involved more than 170 scientists from different global institutions, had its results published in the magazine Science on February 12, 2026. The detection and detailed characterization of these celestial bodies were possible thanks to the combination of data from terrestrial and space observatories. The Cheops satellite, from Agência Espacial Europeia (ESA), played a key role in capturing the variations in light needed to confirm the nature of the most distant planet.

The data shows that the outer planet, named LHS 1903 e, maintains a rocky composition despite its remote location in relation to the host star. The Essa feature is considered an anomaly by theorists, as the outer regions of protoplanetary disks often contain enough volatile materials to form gas giants. The discovery suggests that complex dynamical mechanisms acted during the evolution of this stellar system.

Experts indicate that this finding not only expands the catalog of exoplanets, but forces the scientific community to review traditional theories of planetary formation. The existence of a solid world orbiting beyond planets with dense atmospheres raises questions about planetary migration and the distribution of materials in the disks of dust and gas that give rise to stellar systems.

Detailed architecture of the LHS 1903 system

The planet closest to the star, identified as LHS 1903 b, completes its orbit in an extremely short period of approximately 2.2 days. Sua rock composition is consistent with that expected for worlds subjected to intense stellar radiation, which tends to dissipate any primordial gaseous envelopes, leaving only the solid core exposed. Este pattern is often observed on exoplanets that orbit very close to their host stars.

Just after the first planet, there are LHS 1903 c and LHS 1903 d. Ambos present characteristics typical of mini-Neptunes, with longer radii and lower densities, indicating the presence of thick atmospheres. The formation of these bodies generally occurs in colder regions of the protoplanetary disk, where gas can be gravitationally captured around the forming nuclei, creating the observed dense atmospheric layers.

The big surprise of the system lies in the fourth component, the LHS 1903 e. Diferente of its immediate neighbors, this celestial body has not retained a significant gaseous atmosphere, presenting itself as a rocky planet. Sua detection required extreme precision, as signals from smaller and distant planets are often obscured or confused with stellar noise in conventional astronomical surveys.

All four planets orbit the red dwarf in a compact arrangement, with periods ranging from 2.2 to 29.3 days. The proximity between the orbits facilitates the study of gravitational interactions and frequent transits, transforming the LHS 1903 system into an ideal natural laboratory for testing hypotheses about orbital dynamics in red dwarf systems.

The role of technology in identification

The Cheops satellite mission focuses specifically on the characterization of already known exoplanets, refining radius and mass measurements to determine the density and, consequently, the composition of the planets. In the case of LHS 1903, the space telescope was able to detect the subtle transit of the outer planet, which had gone unnoticed in previous observations carried out by other instruments.

The sensitivity of Cheops allowed astronomers to isolate the signal from the fourth planet and confirm its rocky nature. The combined analysis of photometric transits and radial velocity measurements provided a complete picture of the masses and sizes of the four worlds, solidifying the evidence for an inverted architecture from what is considered standard.

Hypotheses about atypical formation

Classic models of planetary formation establish that rocky planets arise in the inner regions, where stellar heat prevents the condensation of ice and gases, while gas giants form in the outer regions, rich in volatile material. The LHS 1903 system contradicts this logic, requiring alternative explanations for the genesis of the outer rocky planet.

The researchers work with three main scenarios to explain this anomaly:

– Late Formação: The planet may have formed when the protoplanetary disk was already low on gas, preventing the accumulation of a thick atmosphere.

– Migração planetary: Interações violent gravitational forces may have altered the original positions of the planets, pushing a rocky body to the periphery.

– Cosmic Colisões: Gigantic Impactos could have removed the gaseous envelope of a planet that was originally a mini-Neptune, leaving only the rocky core.

Each of these hypotheses requires advanced computational simulations to verify their viability within the physical parameters observed in the system. Determining the exact mechanism will help refine planetary evolution models applicable to red dwarfs.

Relevance to modern astronomy

The discovery at LHS 1903 is significant because red dwarfs are the most common stellar type in Via Láctea, representing about 75% of the stellar population. Compreender How planetary systems organize themselves around these stars is crucial to estimating the prevalence of rocky and potentially habitable planets in the galaxy.

The system also offers a unique opportunity to study the “radius valley,” an observed gap in the size distribution of exoplanets that separates super-Earths from sub-Neptunes. Ter examples of both types of planets in the same system eliminate variables such as the age and composition of the star, allowing direct and more accurate comparisons.

Future observations using equipment such as Telescópio Espacial James Webb could investigate the presence or absence of tenuous atmospheres on the outer planet. Esses data will be decisive in validating formation theories and understanding whether the architecture of LHS 1903 is a rare exception or a common configuration not yet detected on a large scale.