LOS ANGELES — A NASA spacecraft for the first time has arrived at a dwarf planet to begin a 16-month exploration.

The space agency on Friday confirmed that the Dawn craft entered orbit around Ceres in the asteroid belt between Mars and Jupiter.

Unlike other orbit captures that require thruster firings to slow down, Dawn gradually slipped into place.

The encounter occurred when Dawn was pointed away from Earth so it took some time before flight controllers could confirm the craft was healthy.

Ceres is the second and final stop for Dawn, which previously visited the asteroid Vesta.

Here are six essential facts about Ceres and the Dawn mission:

1

Until Friday, Ceres had been the largest unexplored space rock in the inner solar system.

2

Ceres was spotted on New Year’s Day in 1801 by Italian monk and astronomer Giuseppe Piazzi who was searching for a star. It was the first object discovered in the asteroid belt, a zone littered with rocky debris left over from the formation of the sun and planets 4½ billion years ago.

3

Piazzi named the object “Ceres Ferdinandea” after the Roman goddess of harvest and in honor of King Ferdinand IV of Naples and Sicily. Other astronomers shortened it to Ceres. The word cereal also has its origins in Ceres. The chemical element cerium, discovered in 1803, was named after Ceres.

4

Located about 250 million miles from the sun, Ceres was deemed a comet when it was first discovered. Then it was promoted to a planet and later downgraded to an asteroid. Since 2006, it has been classified as a dwarf planet like Pluto, the one-time ninth planet. Dwarf planets are spherical in shape like planets, but they share the same celestial neighborhood with other similar-sized objects.

5

Ceres — with a diameter of about 600 miles — is thought to have a rocky core surrounded by an icy mantle. Long ago it might have harbored an underground ocean. As Dawn approached Ceres, it spotted a pair of puzzling bright spots inside a crater. Scientists think the shiny dots may be exposed ice or salt.

6

Launched in 2007 and powered by ion propulsion engines, Dawn will make the first close-ups of a dwarf planet. It will study Ceres for 16 months from varying altitudes, getting as close as 235 miles above Ceres’ surface, or the distance of the International Space Station above Earth. The spacecraft will take sharper images of the mysterious spots and use its instruments to confirm whether Ceres’ surface is still active and spewing plumes of water vapor.

This summer, another NASA spacecraft dubbed New Horizons will make the first visit to the dwarf planet Pluto.

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For more on the Dawn mission: Click here.