This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Analyzing a sample of 300 of the best-characterized planetary systems among the more than 1,000 known in the Milky Way, an international research team led by the Italian National Institute for Astrophysics (INAF) has discovered that the multiplanet systems identified so far belong to two distinct "families." The study, published in Nature Astronomy, demonstrates for the first time a true "genetic link" between the host star and its planets that shapes the birth, dynamical evolution and future stability of the entire planetary system. The first family consists of wide, massive systems, often with total masses between twice and 10 times that of the solar system, orbiting stars more massive and richer in metals (i.e., elements other than hydrogen and helium) than our sun.
The second family includes compact, lower-mass systems consisting of planets with comparable masses and sizes—in a configuration known as "peas-in-a-pod." These planets orbit stars with mass and metallicity equal to or lower than those of the sun, at distances that, in most cases, are much smaller than Mercury's distance from the sun. To distinguish them, the researchers used a series of parameters that allow comparisons of the characteristics of such different systems. For example, systems in the first family have a high "dynamical temperature." Measured by a parameter that quantifies the system's deviation from an unperturbed configuration with all circular orbits in the same plane, this characteristic traces a past marked by violent gravitational instabilities, giant collisions and planetary ejections.
Members of the second family, by contrast, show traces of less violent dynamical histories, closer to that of our solar system. "The fundamental question we started from was: What determines the characteristics of planetary systems as we see them today? Are they established at birth or sculpted by evolution over time?
The truth, in the end, turned out to lie somewhere in the middle," explains Diego Turrini, an INAF researcher and co-first author of the article. "Our results show that there is a genetic link between planetary systems and their stars, and that, depending on the star around which they are born, this link also determines their fate." Even modest variations in the planet formation environment, due to different stellar properties, can radically change the nature of the forming system and its future evolution, determining whether it will be characterized by phases of marked instability and giant impacts. "The main difficulty during the data analysis was determining whether the two families of planetary systems were real or just an illusion created by the technological limits of current observational techniques," adds Camilla Danielski, a researcher at the University of Valencia, former INAF postdoctoral fellow and co-first author of the work.
"In the end, it became clear that selection effects acted as the tip of the iceberg, revealing the existence of much deeper structural differences between these systems." Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. d research that matter—daily or weekly. A series of numerical simulations exploring the evolution of planetary systems with different initial conditions was also essential to proving this hypothesis. "The scenarios that best reproduce the dynamical properties of the family of wide and massive systems are those in which the systems are unstable from birth," emphasizes Danae Polychroni, an INAF researcher who supervised this part of the study.
"The greater abundance of material from which planets form around their host stars causes them to be born too large, preventing the system from remaining stable." The discovery clarifies how the native stellar environment directly affects planetary fates and the survival of worlds potentially capable of hosting life. Understanding this link is essential to guiding the search for planetary architectures similar to the solar system and for potentially habitable planets like Earth. Diego Turrini, Two families of multi-planet systems with distinct architectures and stellar hosts, Nature Astronomy (2026).
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