Traveling at a speed of 30,800 miles per hour, New Horizons zoomed by Pluto a scant 7,800 miles away. This is the closest we have ever got to Pluto and it will send back some of the best images of the maligned dwarf planet we have ever seen. Maybe this will convince those scientists to let it back into the club and give us the nine planets that we deserve.
This morning, NASA announced that Pluto is 2,370km (about 1,473 miles) in diameter, give or take 20m. That makes it ever so slightly bigger than Eris, a much darker and denser object that lives farther out in the Kuiper Belt. (Eris measures 2,336km in diameter.) Measurements of Pluto's size before today were estimates at best, their accuracy skewed by the dwarf planet's hazy atmosphere.
We've also learned that Pluto has a pretty big ice cap, filled with lots of nitrogen and frozen methane. (I could've told you the place was cold nine years ago.)
Since this mission happened billions of miles away and it takes four hours for the radio waves New Horizon sends us to be uploaded, we shouldn't expect to see any pictures filled with happy, waving aliens until tonight.
Also, by the way, the download speed on that information is 1 Kb/s. Dialup hell.
Here's a video explaining the delicacy and scale of this Pluto flyby:
As we got closer to the dwarf planet, however, all anyone could see was the image of Mickey Mouse's dog, carefully hidden within the terrain.
Pluto, a distant icy dwarf planet, orbits the Sun 29 times farther out than the Earth and has estimated surface temperatures of -380 degrees Fahrenheit (-229 degrees Celsius). These frigid temperatures are far too cold to allow liquid water on Pluto's surface. Its location and small size make it very difficult to observe; however, with NASA's New Horizons mission slated to reach the distant world next year, scientists hope to map Pluto and its moons in great detail.
Current models predict one moon in particular, Charon, is of great interest to study. The models indicate Charon has surface fractures, indicative of a possible subsurface ocean. Further analysis is needed to determine in the moon's interior is warm enough to support liquid water.