Why is exciting planet discovery called “Goldilocks,” and what is its actual name?

This week, excitement was stoked by the discovery of a “Goldilocks planet” within our astronomical neighborhood. Located about 20 light years away in the constellation of Libra, the exoplanet in question has temperatures ranging from –25 to 160 degrees Fahrenheit , orbits its star from a distance of .146 Astronomical Units (about 14 million miles), and has a mass 3 to 4 times that of the earth. In other words, this planet falls within the zone scientists have determined as “just right” for habitability — not too hot, not too cold, not too far from its sun (or too close.)

Unofficially, the planet has been called Zarmina’s World, after the wife of the astronomy team’s leader Stephen Voigt. However, no official means to name an exoplanet exists. The planet naming protocol to date is to designate the planet’s star and a lower case letter starting with b (the star itself is considered the “a”). In this case, being the sixth planet from the star Gliese 581, the planet is called Gliese 581g.

The star Gliese 581 is a red dwarf that is part of the Gliese Catalogue of Nearby Stars, one of 965 stars within 20 parsecs of earth surveyed in 1957. That means there are 965 stars dubbed Gliese – it does not have a unique designation such as Sirius or Polaris.

Gliese581g is tidally locked to its star, so one side of the planet gets constant light and the other side is constantly in darkness. NASA scientists say the most habitable zone on the planet would be at the terminator, or the line between shadow and light. The planet’s sidereal day equals its orbit of its star, 37 days. Although it is yet to be determined, scientists are hopeful that Gliese 581g has water, an indication that will highly support the possibility of life.

A note about Goldilocks: In the earliest versions of the “Three Bears” story, there was no blond trespasser. The interloper was either an old woman, a “silver-haired” girl, or a fox.