Jul 02, 2013 04:07 PM EDT By Russell Westerholm, UniversityHerald Reporter

The International Astronomical Union (IAU) voted against naming one of Pluto's moons "Vulcan" and named the moons "Kerberos" and "Styx," Space.com reported.

The IAU has always been responsible for deciding the names of celestial objects and ruled that Pluto's moons should be named after mythological characters of the underworld from Roman and Greek mythos. Mythology states that Pluto was the ruler of the underworld.

Click here for images of Pluto and its moons.

Actor William Shatner, who portrayed James T. Kirk, captain of the U.S.S. Enterprise of "Star Trek" TV series, suggested one of the moons be named "Vulcan," the home planet of Kirk's friend Mr. Spock. In an online poll hosted by the Search for Extraterrestrial Intelligence (SETI), the Trek-themed named received more votes than any other name, but the IAU decided against it.

"The IAU gave serious consideration to this name, which happens to be shared by the Roman god of volcanoes," SETI officials wrote in a statement. "However, because that name has already been used in astronomy, and because the Roman god is not closely associated with Pluto, this proposal was rejected."

"Kerberos," is the Greek equivalent to the three-headed dog named "Cerberus" in Roman mythology. "Styx" is a river that separates the living from the dead.

NASA's Hubble Telescope discovered Kerberos in July 2011 and was named P4 until now. Styx, formerly P5, was spotted on year later in July 2012.

Pluto has three other moons named Nix, Hydra and Charon, which is the largest. Both Kerberos and Styx are estimated to be between 15 and 20 miles in diameter.

NASA's New Horizon spacecraft is scheduled to fly by Pluto and its orbiting moons sometime in 2015 and will take close-up shots of the little-explored dwarf planet.

Shatner took to Twitter following the announcement to voice his disappointment with "Vulcan" being overlooked as a name.

"They didn't name the moon Vulcan. I'm sad," he posted Tuesday.

They didn't name the moon Vulcan. I'm sad.

— William Shatner (@WilliamShatner) July 2, 2013

Shatner, who promoted the online vote, joked on Twitter that the IAU are "probably Star Wars fans" and asked what Princess Leia actress Carrie Fisher was up to. Fisher did not respond to Shatner's joke, but also has not posted on her verified account for nearly a month.

I think they used us for promotional purposes! They're probably Star Wars fans! Where's Fisher?!!! She's been too quiet lately. — William Shatner (@WilliamShatner) July 2, 2013

See Now: Covert Team Inside Newsweek Revealed as Key Players in False Human Trafficking Lawsuit