Milky Way Not Alone in Habitable Planets
This research suggests that the type of galaxy significantly impacts the age of alien worlds.
Galactic Habitability: A Cosmic Question
New research indicates that up to 0.8 percent of stars in large galaxies might host planets capable of supporting life.
Astronomers R. Gobat and S.E. Hong investigated how suitable different types of galaxies are for hosting life-supporting planets and how this has evolved over time.
The Model and Its Scope
They utilized a detailed computer model simulating galaxy evolution, from energetic "star-forming" to quieter "passive" galaxies.
Model Parameters:
Galaxies ranging from 100 million to 300 billion times the mass of our Sun.
Key Findings on Habitability
The study focused on star formation, chemical composition, and the conditions for a "circumstellar habitable zone" – the region around a star where a planet could sustain liquid water on its surface.
Habitability Trends
- A galaxy's habitability changes only slightly with its mass.
- Galaxies approximately 40 billion times the Sun's mass showed the highest potential today.
Between 0.65 percent and 0.8 percent of all stars in galaxies more massive than 1 billion Suns are expected to host planets in their habitable zone.
Galaxy Type and Planet Age
Passive galaxies, which are no longer actively forming new stars, tend to have slightly higher habitability than star-forming galaxies.
Median Age of Potentially Life-Supporting Planets
- Star-forming galaxies: Around 6 billion years.
- Passive galaxies: A more ancient 10 billion years.
The study also suggests that if Earth is not unique, the probability for intelligent life to evolve on a suitable planet should be lower than "7 × 10^-10."
"The habitability of galaxies has not changed significantly in the last ~8 Gyr," the authors state, meaning most habitable planets in disk galaxies formed long before our solar system.
Limitations and Future Research
The study acknowledges limitations, including simplified galaxy structures and limited consideration of galaxy mergers. Future research could explore these complexities and uncertainties regarding planet distribution.
This research provides a framework for understanding where and when life might emerge across the vast universe.
Source:
R. Gobat and S.E. Hong "Evolution of galaxy habitability" Astronomy & Astrophysics, 2018.