Comparison of the habitable zone of 40 Eridani with the habitable zone in our solar system.
NASA?s upcoming planet-finding mission SIM PlanetQuest will scan the star system 40 Eridani for signs of a habitable planet.
If found, that planet would be the real-life counterpart of the fictional planet of "Vulcan," well-known in the "Star Trek" universe as the home of Admiral (formerly Mr.) Spock and the entire Vulcan race.
The Space Interferometry Mission (SIM) PlanetQuest, which is overseen by NASA's Jet Propulsion Laboratory in Pasadena, California and slated to launch in 2015, is an orbiting interferometer that will link a pair of telescopes to function as a much larger "virtual telescope."
40 Eridani, a triple-star system 16 light-years from Earth, includes a red-orange K dwarf star slightly smaller and cooler than our Sun. While the planet of Vulcan was not identified with a particular star for many years, "Star Trek" creator Gene Roddenberry endorsed 40 Eridani as Vulcan's sun in a letter published in the July 1991 issue of Sky & Telescope magazine.
Caltech researcher Angelle Tanner, who proposed the idea that SIM might be able to detect Vulcan, had two questions: Can a planet form around 40 Eridani A? Can SIM detect such a planet?
Sean Raymond, a planetary theorist at the University of Colorado, Boulder, had the answer.
"Since the three members of the triple star system are so far away from each other, I see no reason why an Earth-mass planet would not be able to form around the primary star, 40 Eridani A," he said.
The stars of 40 Eridani lie hundreds of astronomical units (AUs) apart. One AU is the distance between the Sun and Earth, or about 93 million miles (149 million kilometers).
If Vulcan life were to exist on the planet, the orbit of the planet would have to lie in a "habitable zone" around the star where liquid water could exist, which would be at a distance of 0.6 astronomical units from 40 Eridani A. The Vulcans would have a year of about six months.
Water is, of course, a necessary ingredient in plomeek soup, Spock's favorite. (He has been known to sometimes throw it across the room at Nurse Chapel when suffering the early effects of the pon farr, the Vulcan mating ritual.)
In determining if SIM could spot such a planet, Tanner used a set of mathematical models based on Newton's Laws. She was thus able to conclude that SIM would be able to definitively determine whether there is an Earth-mass planet orbiting in the habitable zone around 40 Eridani A, and could also determine its orbit. This is because the SIM PlanetQuest instrument will be so accurate, it could measure the thickness of a nickel at a distance from Earth to the moon.
The prospect of spotting this planet is quite exciting, since NASA's Terrestrial Planet Finder mission, planned for launch after SIM, would not only be able to take a rudimentary "picture" of the planet, but could also search for signatures of life such as methane and ozone.
The SIM oservatory will attempt to detect planets by looking for wobble in the positions of nearby stars, which may indicate that orbiting planets are pulling at them. Also, the mission will determine positions and distances to stars several hundred times more accurately than current technology allows. SIM will open an era of what NASA calls "precision astrophysics." It will permit the construction of a "street map" to the Milky Way galaxy.
When asked what life would be like on Vulcan, Tanner speculated that the inhabitants might be pale.
"A K dwarf star emits its light at wavelengths which are a bit redder compared to those from the sun, so I wonder whether it's harder to get a tan there," she said.
Trekkies know that the fictional Vulcan is hot and dry, with large deserts, so the native inhabitants would of necessity spend a great deal of time in the sun. If the Vulcans, with their copper-based blood, did tan, their tans would be, of course, of a dark greenish color.
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