It's official: NASA's New Horizons became the first spacecraft ever to fly by Pluto today, passing within 7,750 miles of the dwarf planet at 7:49 am ET.
This fact was widely celebrated this morning (including on this site), but in reality no one knew whether the probe successfully made it until scientists received a signal this evening. That's because New Horizons was busy collecting data during the flyby — not transmitting it — and once it did send a signal, the transmission took 4.5 hours to reach Earth.
Now, after receiving the signal this evening, mission scientists have confirmed that the probe made it through as planned (there was roughly a 1-in-10,000 chance it could have been hit by a piece of errant space debris). The first photos of the encounter should arrive sometime tomorrow, and over the next weeks and months, we'll see gorgeous, high-resolution photos of Pluto — 10 times sharper than anything taken so far.
New Horizons traveled 3 billion miles to get to Pluto
But even moving at speeds as high as 50,000 miles per hour, it took nearly a decade to reach Pluto because of a simple fact: It's incredibly far away. By analogy, if you imagine the Earth to be a basketball, Pluto would be a little larger than a golf ball — and at the same scale, that golf ball would be 50 to 80 miles away.
This distance also means that the craft had to be fairly light (about 1,000 pounds) to get there in a reasonable amount of time, which precluded it from carrying enough fuel to slow down to enter Pluto's orbit. Consequently, it was moving at about 31,000 miles per hour during the flyby — and traversed the diameter of Pluto in just a few minutes.
New Horizons is about to reveal Pluto for the first time
Until very recently, the best photos we had of Pluto (taken by the Hubble Space Telescope) showed it as a blurry blob:
New Horizons quickly surpassed the quality of those images during the past few weeks of its approach to Pluto, capturing much sharper images of the dwarf planet and its moons. But even this will be outdone by the photos taken today during the actual flyby, which are projected to be 10 times sharper.
We should see the first of these Wednesday afternoon, and the rest should trickle in over the coming weeks because New Horizons is only capable of transmitting data at a very slow rate.
They should reveal a fascinating new landscape, shedding light on the ice caps and plains scientists have spotted in recent images, as well as features we simply haven't seen yet.
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