Life Beyond Earth

Are we alone, or is there life beyond Earth? It’s a question we’ve been trying to actively answer for decades now, with increased interest in more recent times. While there almost certainly is life outside of our world, we have yet to find it. Based on our understanding of the spectrum of organisms that live on Earth and the conditions that life needs to thrive, we can hypothesize what other life-bearing planets may look like. Using this basic approach, a newly developed computation method estimates that there may be more than 100 million planets in our Milky Way galaxy that could be home to complex life.

This computation method takes into account several factors that affect whether life can survive on a planet. For example, a planet’s size and temperature are two main ones to consider — a planet should be 0.1 to 10 times the mass of Earth (to support the right type of atmosphere), and not too much hotter or colder than Earth (to allow water to be in a liquid form). The distance of the planet from its central star is also essential and affects the planet’s temperature. (Its similarity in size and likely temperature are reasons why the recently-discovered Earth-sized planet of Kepler-186f attracted much attention as a possible life-bearing planet.)

Planetary density, the planet’s substance (if it is liquid, solid, or gas form) and general chemistry, and the planet’s age were other factors also taken into consideration when developing this new computation method that predicts there to be more than 100 million planets in the Milky Way galaxy capable of supporting complex life.

But while this may seem like a large number of life-bearing planets, the vast, empty space between planets makes meeting and studying such potential life forms virtually impossible in the near future. One of the most promising systems, Gliese 581, has two planets that look like they should be able to support complex life, but even this “close” system is about 20 light years away from us.

So while we should surly continue efforts to detect life on other planets, we must also work to improve our means of traveling through space so that when/if we find other life, we will not lose the opportunity to someday see what it looks like up-close.

For further reading:

• Louis N. Irwin, Abel Mendez, Alberto G. Fairen, and Dirk Schulze-Makuch’s article “Assessing the Possibility of Biological Complexity on Other Worlds, with an Estimate of the Occurrence of Complex Life in the Milky Way Galaxy”
• ScienceDaily’s article “Milky Way may bear 100 million life-giving planets”
• National Geographic’s article “The Hunt for Life Beyond Earth”
• Biology Bytes’ article “Potentially Habitable Earth-Sized Planet Discovered”