Dwarf Planet of the Day: We #Flyby Pluto and Learn Lots About the Edge of Our Solar System

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It took nine years and 3 billion miles, but at 7:49 a.m. EST the New Horizons spacecraft passed what was once the furthest planet in our solar system.

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.

But we've learned a lot so far. For instance, now we know how big the dang thing is.

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.

Mars Express Makes a Close Flyby of Phobos

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As the spacecraft passes close to Phobos, it will be pulled slightly off course by the moon's gravity, by a few tens of centimetres. This small deviation will be measured using the spacecraft's radio signals, and then translated into measurements of gravity, mass and density at different locations on the moon.