In the far reaches of the solar system, beyond Neptune, there is a minor planet orbiting the sun in a sea of icy debris.
Humans have known about the reddish, round object for more than a decade. Since 2007, scientists have estimated that it has a diameter of 775 miles — about half the size of Pluto — and most likely has methane on its surface.
But they still don’t know what to call it.
This week, the astronomers who discovered the minor planet said they wanted the public to weigh in on the chosen name. Offering up three options to choose from, they invited anyone to vote on the name that they will eventually submit to the International Astronomical Union, which must approve the official name.
Using data from the union’s Minor Planet Center, the astronomers who discovered the minor planet, which is currently referred to as 2007 OR10, estimate that it is the largest unnamed world in our solar system. The group has designated a total of nearly 525,000 minor planets in our solar system.
Meg Schwamb, an astronomer who first set eyes on the minor planet as a graduate student in her 20s, said she felt that she and other astronomers finally knew enough about the minor planet to give it a name.
Dr. Schwamb, 34, was working on her thesis at Caltech in 2007 when she and two other astronomers, Mike Brown and David Rabinowitz, conducted a survey to find small bodies far out in the solar system with a robotic telescope. The telescope took images of the same patch of sky over time, allowing the scientists to discern any moving objects.
Dr. Schwamb said that 2007 OR10 started out as just a point of light on her computer. Over the years, she and other scientists learned more about it: that the planet was icy, that it had a moon to call its own and that it rotated slowly compared with other objects in the Kuiper belt, the far-out ring of icy debris.
The team of astronomers believe that it is mostly likely a dwarf planet, but the astronomical union has not yet designated it as such. A dwarf planet is a celestial body that orbits around the Sun, has enough mass for gravity to make it round and has not cleared the neighborhood around its orbit.
“We know enough about it now where we think we can give it a fitting name,” Dr. Schwamb said in a phone interview.
Dr. Schwamb likened the process to parents naming a baby after they meet it. Except that this planetary get-to-know-you process took more than a decade.
The astronomers’ caution is understandable, considering that their first attempt at giving 2007 OR10 an informal nickname didn’t go so well. In 2011, Dr. Brown wrote in a blog post that they nicknamed the minor planet Snow White, assuming that it would have a bright white, icy surface.
“But when we went to the telescope and measured it, Snow White was not white,” Dr. Brown wrote. “In fact, Snow White is one of the reddest objects ever found in the Kuiper belt.”
In choosing the three possibilities for 2007 OR10’s formal name, the astronomers had to adhere to the astronomical union’s rule that minor planets in the Kuiper belt that have similar orbits must be named after mythological figures associated with creation.
The first choice listed is Gonggong, a Chinese water god with red hair and the tail of a serpent. The second, Holle, is the name of a European winter goddess associated with yuletide. And the third, Vili, is a Nordic deity who, according to folklore, helped kill a giant to create the universe.
The scientist who discovers a minor planet is typically given the opportunity to name it, but Dr. Schwamb said this particular christening felt momentous enough to involve outside observers.
“I wanted a piece of that naming, and I wanted to share it with the rest of the world,” she said.
The voting, which opened Tuesday, will close on May 10.
Emily Lakdawalla, a senior editor for the Planetary Society, which helped publicize the naming contest, said there was a long list of rules that planetary names must follow in order to be approved.
Naming minor planets after pets, for example, is frowned upon. And the names of people or events associated with political or military history are unsuitable until a century after the person died or the event occurred.
Ms. Lakdawalla said that involving the public in astronomers’ work gives the public the rare chance to be a part of space exploration. It has happened during space shuttle launches and when NASA releases images or sound taken from its spacecrafts, but those moments are relatively rare.
“It doesn’t impact most people’s everyday lives,” she said, “but when it does come across their lives, it tends to excite and inspire people.”