NASA's New Horizons mission has revealed the exact size of Pluto for the first time, and it's slightly larger than we thought it was.
The findings confirm past suspicions that Pluto is the largest object in our solar system beyond the orbit of Neptune, NASA reported. New Horizons revealed the dwarf planet is 1,473 miles in diameter.
"The size of Pluto has been debated since its discovery in 1930. We are excited to finally lay this question to rest," said mission scientist Bill McKinnon, Washington University, St. Louis.
Pluto's newly measured size suggests its density is lower than what was previously estimated and its ice content is slightly higher. The findings also suggest the lowest layer of Pluto's atmosphere, called the troposphere, is shallower than what was previously believed.
In the past, measuring Pluto's size has been a challenge because of its troublesome atmosphere. Now, new images acquired with the Long Range Reconnaissance Imager (LORRI) has made sizing up the dwarf planet possible.
Pluto's largest moon Charon lacks a substantial atmosphere, so it has generally been easier to measure using ground-based telescopes. The New Horizons observations have confirmed the moon's previously estimated size of 751 miles across. LORRI has also turned its eye on two of Pluto's smaller moons, Nix and Hydra.
"We knew from the time we designed our flyby that we would only be able to study the small moons in detail for just a few days before closest approach," said New Horizons Principal Investigator Alan Stern of the Southwest Research Institute, Boulder, Colorado. "Now, deep inside Pluto's sphere of influence, that time has come."
The New Horizons images suggest Nix is about 20 miles across and Hydra is roughly 30 miles across. The images reveal bright surfaces on the moons that may indicate ice cover. Pluto's two smaller moons, Kerberos and Styx, are fainter and more difficult to measure. The scientists believe they will be able to gain more insight into their size during the upcoming flyby.
