Today, Feb. 18, the international science community celebrates the 91st anniversary of the discovery of Pluto, which was reclassified from a major planet to a dwarf planet in 2006. 

It was Clyde William Tombaugh, an American astronomer, who discovered Pluto in 1930.

Here are 10 things you need to know about Pluto as contained in United States’ National Aeronautics and Space Administration's (NASA) real time science encyclopedia of deep space exploration called "Science Solar System Exploration.”

1. Pluto is about 1,400 miles (2,380 km) wide. That's about half the width of the United States, or 2/3 the width of Earth's moon.

2. Pluto orbits the Sun about 3.6 billion miles (5.8 billion km) away on average, about 40 times as far as Earth, in a region called the Kuiper Belt.

3. A year on Pluto is 248 Earth years. A day on Pluto lasts 153 hours, or about six Earth days.

4.Pluto is officially reclassified as a dwarf planet.

5.Pluto has a thin atmosphere of nitrogen, methane and carbon monoxide. The atmosphere has a blue tint and distinct layers of haze.

6.Pluto has five moons. The largest, Charon, is so big that Pluto and Charon orbit each other like a double planet.

7.Pluto has no ring system.

8.The only spacecraft to visit Pluto is NASA’s New Horizons, which passed close by in July 2015.

9.Pluto’s surface is far too cold, -378 to -396 degrees F (-228 to -238 C), to sustain life as we know it.

10.The 11-year-old girl from Oxford, England named Venetia Burney suggested the name Pluto in 1930. He proposed to her grandfather that the new discovery be named after the Roman god of the underworld and the latter forwarded her granddaughter’s suggestion to the Lowell Observatory and it was chosen.