Astronomers find that a surprising number of exoplanets could host life
A new study suggests some stars could host up to seven habitable planets, far more than Earth’s solar system. Could life exist in such systems?
Astronomers have discovered that some stars could support up to seven Earth-like planets. (CREDIT: CC BY-SA 4.0)
For years, astronomers have searched the cosmos for planets capable of supporting life. Most efforts focus on the "habitable zone," the region around a star where a planet could have liquid water. But new research suggests that some stars may host far more habitable planets than our own Sun.
A recent study led by Stephen Kane, an astrobiologist at UC Riverside, challenges the idea that planetary systems are limited to a single habitable world. According to Kane, under the right conditions, a star could support up to seven Earth-like planets—far more than the one habitable planet found in our solar system.
The Role of Planetary Arrangements
The study, published in the Astronomical Journal, examines planetary system stability using complex computer models. These simulations tested how planets of different sizes interact over millions of years. The results reveal that a solar system’s layout is key to its habitability.
In compact planetary systems, multiple planets can coexist in habitable zones without disrupting each other’s orbits. However, as more planets are added, their gravitational influence can cause instability.
"More than seven, and the planets become too close to each other and destabilize each other's orbits," Kane explained. To maintain habitability, planets must follow nearly circular orbits to avoid catastrophic collisions.
The Influence of Giant Planets
The study also highlights a major limiting factor in planetary habitability: gas giants. Planets like Jupiter have a profound impact on a solar system’s structure. Jupiter, with a mass more than two-and-a-half times that of all other planets in our solar system combined, plays a disruptive role. "It has a big effect on the habitability of our solar system because it's massive and disturbs other orbits," Kane said.
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Gas giants introduce gravitational perturbations that can eject smaller planets from the habitable zone. This may explain why our solar system, despite having a habitable zone that could support up to six planets, only has one Earth-like world.
Research has shown that M-dwarf stars, which are smaller than the Sun, are less likely to have giant planets, potentially making them ideal hosts for multiple habitable planets.
Searching for Multi-Habitable Star Systems
Astronomers are now turning their attention to nearby star systems that lack a Jupiter-like planet. One promising candidate is Beta Canum Venaticorum (Beta CVn), a star just 27 light-years away. "Because it doesn’t have a Jupiter-like planet, it will be included as one of the stars checked for multiple habitable zone planets," Kane noted.
Beta CVn is of particular interest due to its similarity to the Sun and the lack of known gas giants that could disrupt potential habitable planets.
Observations using NASA’s upcoming Habitable Exoplanet Observatory will allow researchers to directly image any planets in its habitable zone. Scientists are also exploring atmospheric compositions of these worlds, which could provide crucial clues about their potential for life.
Implications for Understanding Earth’s Evolution
Beyond the search for extraterrestrial life, this research offers insight into our own planet's past and future. Studying exoplanets with similar evolutionary pathways to Earth can reveal how environmental conditions change over time.
"By measuring the properties of exoplanets whose evolutionary pathways may be similar to our own, we gain a preview into the past and future of this planet—and what we must do to maintain its habitability," Kane said.
The discovery of systems with multiple habitable planets would reshape our understanding of planetary formation and habitability. It also raises intriguing questions: If other star systems can support several Earth-like worlds, could life exist in multiple places within a single system?
Future missions will continue to explore these possibilities, bringing us closer to answering one of humanity’s greatest questions—are we alone in the universe?
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