The New Horizons spacecraft made its closest approach to the dwarf planet just before 8 a.m. (ET) Tuesday morning, to the hollering, cheering delight of scientists and researchers cheering it on at headquarters. It’s been a heckuva voyage. NASA received a transmission just before 9 p.m., telling the crew on Earth that it is doing fine; it will take several more hours to transmit the massive amount of data gathered. But before the flyby, New Horizons was already sending back images of Pluto and its largest moon, Charon, during its final approach. A photo taken on July 13 was the clearest image of Pluto that anyone has ever seen.
“Once again the United States leads the world in space.” — John Holdren
Now we can see a large, bright feature on Pluto informally named the “heart,” which measures approximately 1,000 miles across, and nearby darker equatorial and mottled terrain. Much of the heart’s interior appears remarkably featureless – possibly a sign of ongoing geologic processes, NASA says. Scientists know that the frigid region around Pluto’s south pole hasn’t seen the sun for 20 years – and won’t for another 80 years – but New Horizons detected what’s possibly ice caps made from frozen molecular nitrogen.
“I’m delighted at this latest accomplishment by NASA, another first that demonstrates once again how the United States leads the world in space,” says John Holdren, assistant to the President for Science and Technology and director of the White House Office of Science and Technology Policy. “New Horizons is the latest in a long line of scientific accomplishments at NASA … As New Horizons completes its flyby of Pluto and continues deeper into the Kuiper Belt, NASA’s multifaceted journey of discovery continues.”
Pluto was discovered just 85 years ago by Clyde Tombaugh, who peered through a telescope at the faintest smudge at the far end of the solar system and realized it was more than a mere blot on his lens. The nearby planets are far more codified in our minds, and easier to reach — a trip to Mars takes about 9 months, for example. New Horizons’ flyby of the dwarf planet and its five known moons took the space agency almost ten years. It was launched in January of 2006, and traveled at speeds of up to 36,373 mph. And, right after it reached Pluto, it was already leaving, speeding away at 31,000 miles per hour.
It’s not alone out there in the inky blackness at the edge of our little quadrant of space. Pluto lives in a region of our solar system called the Kuiper Belt, an outer region populated by icy objects ranging in size from boulders to dwarf planets. Kuiper Belt objects, such as Pluto, preserve evidence about the early formation of the solar system, NASA says.
Despite what we know about Pluto, there’s much we don’t know. In fact, the basic size of the planetoid (or whatever you choose to call it) was a topic of debate until recently.
“The size of Pluto has been debated since its discovery in 1930. We are excited to finally lay this question to rest,” says mission scientist Bill McKinnon, Washington University, St. Louis.
Pluto is 1,473 miles in diameter, somewhat larger than many prior estimates. Images acquired with the Long Range Reconnaissance Imager (LORRI) were used to make this determination in the days leading up to the flyby. This result confirms what was already suspected: Pluto is larger than all other known solar system objects beyond the orbit of Neptune.
Will it regain its status as a planet? Only time will tell.