The Exoplanet Gliese 581d May Support Life

It doesn’t have an exciting name like planets do in Star Wars and Star Trek, but Gliese 581d might be home to life. Heavy emphasis on “might be.”

Gliese 581d is an exoplanet orbiting a red dwarf star called Gliese 581. Gliese 581 is more than 20 light-years from Earth and the 89th closest star to our sun.

The exoplanet (a planet outside our solar system that orbits a star) was discovered in 2007. Then, it was disputed by astronomers, and then, it was not-so disputed by astronomers.

While not 100-percent confirmed, many stargazers now believe Gliese 581d exists.

The Gliese 581 planetary system is quite a mystery. Depending on which astronomer you talk to, Gliese 581 has four or six orbiting planets.

Interestingly, all the aforementioned planets are closer to Gliese 581 then Earth is to the Sun. That’s because Gliese 581 has only 30 percent of the mass of our sun.

Exoplanets are discovered by finding tiny variances in stellar light. It’s an arduous process that involves lengthy and exacting observations.

Astronomers have decided to name exoplanets by using the number of the star they orbit and then adding a lowercase letter. To complicate matters, the letter doesn’t correspond to its order from the celestial body it orbits, but the order in which it was discovered.

The closest planet to Gliese 581 is named “Gliese 581e” while the farthest planet is named “Gliese 581f.” There is no Gliese “581a.”

Gliese 581d may become the first known world, besides Earth, that’s capable of supporting life as we know it.

Astronomers believe the planet lies within the star’s “Goldilocks Zone”—the range of orbits where temperatures are conducive for liquid water. It’s believed that liquid water is key to life.

The atmosphere of Gliese 581d is believed to have plenty of CO2. This creates conditions that are ideal for storing heat. Meanwhile, red light from its sun shines through its atmosphere and keeps surface temperatures optimal for liquid water.

“With a dense carbon dioxide atmosphere—a likely scenario on such a large planet—the climate of Gliese 581d is not only stable against collapse but warm enough to have oceans, clouds, and rainfall,” says France’s National Centre for Scientific Research (CNRS).

Of course, all this talk of atmosphere, liquid water, and life is purely theoretical.

Gliese 581d has been dubbed a “Super Earth.” A fitting name since Gliese 581d is seven times more massive, and its radius is twice that of regular Earth. Super Earth’s year is 67 days.

The exoplanet receives far less sunlight than Earth, around 70 percent less, and its gravity is about twice as strong.

Some scientists believe Gliese 581d might be tidally locked. This means one side of the planet is perpetually stuck in day and the other side is perpetually stuck in night.

Doesn’t sound like a vacation spot? Well, you don’t have to worry about that. With our current space technology, travelers will reach Gliese 581d in about half a million years.

Another planet orbiting Gliese 581, Gliese 581g, also known as “Zarmina,” is a better candidate for liquid water, and therefore life, because its orbit is situated in the middle of the habitable zone. It’s existence, however, is widely disputed.

In 2009, CSIRO, Cosmos magazine, the Australian Government, and NASA teamed to collect goodwill messages and sent them to whomever might be inhabiting Gliese 581d. The messages should arrive around 2030.

Key Astronomy Terms

Exoplanet or Extrasolar Planet – A planet outside of our solar system that’s orbiting a star. 

Gravity – The natural phenomenon where objects with mass are drawn toward each other.

Goldilocks Zone – Planetary orbits that support liquid water if the atmospheric pressure is sufficient.

Light-year – A unit of measurement equal to the distance light travels in a vacuum in a year or 5.9 trillion miles. 

Orbit – The trajectory of an object, curved by gravity, around another object.

Red Dwarf – A small and relatively cool star.  Red Dwarf stars are also the most common type of star in our galaxy. 

Gliese 581 at a Glance

Type: Red Dwarf

Distance from Earth: 20.5 light-years

Constellation: Libra

Mass: 1/3 of the Sun

Discovered: 1886