Buzz
To determine how many planets could sustain life, you need to first establish what 'life' truly means.Key Insights
- Planets capable of supporting life must have liquid water, energy (light or chemical), and essential nutrients. These conditions are surprisingly widespread across the universe.
- Scientists estimate that around 60 billion planets in the Milky Way alone reside within habitable zones that could support life.
- Given the sheer number of galaxies, researchers predict there are approximately 50 sextillion potentially habitable planets in the universe, making Earth just one of many possible hosts for life.
For those unfamiliar, the Drake equation is a tool used to estimate the number of technological civilizations that may exist within the universe.
The issue with the Drake equation is that it doesn’t provide a definitive answer; it merely outlines what might be possible if we identify the correct factors. (Which is unlikely, as these factors are all hypothetical.) While it's fun to imagine a planet inhabited by beings made of putty instead of carbon, that scenario is probably unrealistic. Instead, we need to define the parameters of life on Earth and explore which other planets may meet those criteria.
The criteria are fairly simple. First, we require liquid water. Water dissolves and transports chemicals, enabling critical metabolic reactions. Energy is also necessary to create and sustain life, which can come from light (from a warm sun and atmosphere) or from chemical reactions. Nutrients are essential to form and maintain life. A planet with a water cycle, a habitable atmosphere, or volcanic activity can help replenish and circulate nutrients [source: Lunar Planetary Institute]. While it may seem unlikely to find another life-sustaining planet in the universe, these are fairly specific conditions — maybe there’s one? Two?
Or perhaps there are 60 billion planets in our galaxy alone that could potentially support life.
Yes, that's right — we aren’t as unique as we once thought. In fact, scientists now believe that there are 60 billion planets within the Milky Way located in the habitable zone. The habitable zone is the region where a planet is warm enough to keep water in liquid form without it evaporating into gas [source: Gannon]. These planets must be near a star or have cloud cover to retain moisture. Given the hundreds of billions of stars in the Milky Way, the number of habitable zones is vast.
So, that's the most up-to-date information regarding our own galaxy. But remember, the Milky Way is just one of hundreds of billions of galaxies in the universe. Every galaxy is teeming with stars, each of which could potentially have planets that are neither too hot nor too cold. The best estimate from researchers? 50 sextillion [source: Anthony].
In other words, it’s not entirely feasible for anyone to ‘predict’ how many hospitable planets exist in the universe, considering we're just beginning to understand the planets in our own galaxy. But, at the same time, it’s not out of the question for me to dream that one of them might be made of Play-Doh.
