NASA's New Horizons probe performed its closest flyby of Pluto today at 7:49 AM EST traveling 49,600 km/hr (30,800 mi/hr). Data from this flyby will reach Earth at around 8:50 PM tonight. At the time while I was writing this article, New Horizons has been traveling for 3,463 days, which is about 9.5 years. During this near decade span the probe has traveled 2,965,290,250 miles. In fact New Horizons has traveled so far that scientists don't even keep track of the distance in miles or kilometers anymore, they keep track of distance in astronomical units, abbreviated AU. An AU is the distance from the Earth to the Sun, 93 million miles. New Horizons is 32.91 AU from earth now. I don't think anyone can disagree that is a really far distance from home. New Horizons is so far from home that it takes light 8 hours 50 minutes and 41 seconds to travel the round trip from Earth to the probe. This is important because when NASA communicates with he probe it takes more than one work day for the probe to answer back.
This video shows how fast light travels through our solar system, just to give you an idea of how complicated it is for NASA engineers to communicate with New Horizons.
Why should we care? Well this is the first time in human history that humans have explored every planet in the solar system. This was not an easy task. This exploration mission had its roots in the 1960s when humans first landed on the moon. New Horizons is not only exploring Pluto, but also its five moons: Charon (the largest), Styx, Nix, Kerberos, and Hydra.
The first high-resolution images of Pluto should arrive on Earth at some point tomorrow. New Horizons will send to data to Earth and be picked up by a satellite dish in Madrid, Spain. As for now, preliminary data is trickling in, with a recent false-color image of Pluto and its largest moon, Charon, being made public earlier today.