20 light years away, in the constellation of Libra, sits a red dwarf star, called Gliese 581. This relatively cool body of hydrogen is orbited by six planets; the newly-discovered fourth planet lies inside the “Goldilocks zone”, where the conditions are such that liquid water could exist on the surface and the planet could potentially support human life.

Said planet is estimated to be around 3 or 4 times the size of Earth. Steve Vogt, a Santa Cruz astrophysicist and its discoverer, named it “Zarmina’s World”, in honour of his wife. Though resting within the habitable “Goldilocks” zone of its solar system, life on Zarmina would be considerably different from life on Earth; the planet has an orbital period of just under 37 days and orbits its red star at about a 1/6th the distance of our Earth to our Sun. What complicates the prospect of inhabiting Zarmina is this close proximity to its star. The gravitational pull exerted by the latter is immense. This results in the planet being “tidally locked” to Gliese 581, so that one side always faces it and would therefore be too hot to live on, while the other faces pitch-black darkness and thus would be too cold.

It is the territory in between these two sides that has scientists excited, as there, theoretically, it would be possible for life to evolve. This territory is in perpetual twilight, always between day and night, and temperatures can vary from 71 degrees Celsius to – 34, depending on the longitudinal position — it is said to get warmer near the equator and colder near the poles. Initially, scientists suspected that the nature of this “tidally locked” planet would result in winds so strong, no human could live on it. Using 3D climate models, Vogt concluded that these winds are in fact only about 30-40 mph on the hot side and 0-10 on the cold side. These models also inferred that the heat from the hot side would be carried to the cold side and thus somewhat even out the temperature.

On Zarmina’s surface, gravity is thought to be around twice as much as on Earth. Vogt, ever the optimist, describes this as a good thing, as it means there is less of a chance of the atmosphere escaping. This is not to say that Zarmina necessarily has water or an atmosphere we could breathe in. The planet was discovered through the Doppler Shift method by which astronomers identify a change in the wavelength of light emitted by a star. From this, only the relative mass of the planet, its orbit and its distance from the star can be determined. No environmental data about the planet is known and any talk about water or atmosphere is pure speculation. The planet Gliese 581d, which lies in the same system, orbits farther out, but if it has a thick enough atmosphere, could also potentially support liquid water on its surface.

Nevertheless, Vogt remains convinced that there is life on the planet; controversially, he has claimed that it would be easier for life to evolve on Zarmina than on Earth.

“The chances for life on this planet are 100 percent”, he says. His co-discover, Paul Butler, though less enthusiastic about the idea of life on Zarmina, acknowledges the fact that anywhere you find water on Earth, you find life, and the same can be said about anywhere in the universe, including the Gliese system.

Sadly, it is unlikely that humans will be visiting Zarmina for a very long time; with our current technology, it would take circa 180,000 years to travel there. Still, the planet’s significance doesn’t lie in whether we can visit it or not, but more in the fact that it was found in our own “stellar backyard”. This provides evidence that earth-like planets in the habitable zones are likely to be very common, and hopefully, that we are not the only living things out there.

Daniel Fine

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