By Sean O’Kane,The Verge, July 13, 2015 – “Fasten your seat belts — New Horizons has arrived at the Pluto System.” Those were the words of Alan Stern, New Horizons’ principal investigator, at the Monday morning briefing. After more than nine years and 3 billion miles, the spacecraft is inside the dwarf planet’s Hill sphere of influence and ready to take the first detailed measurements and photographs of Pluto.
New Horizons is already well within 1 million miles of Pluto and is rapidly approaching the 31,000 mile per hour flyby that will bring it within 7,800 miles (about 12,500km). Below you’ll find a schedule of what’s happening when, as well as when NASA will be doing live streams of the events here at the Johns Hopkins Applied Physics Laboratory in Columbia, Maryland. But first, if you’re not sure why we’re heading to Pluto in the first place, our sister site Vox has put together a wonderful 3-minute primer:Click Here.
What have we learned so far?
The New Horizons team has already solved one of the biggest mysteries about Pluto: its size. 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.
This morning also brought confirmation that Pluto has an icy polar cap, which is made of a mix of frozen methane and nitrogen gases. And while scientists had theorized that Pluto’s thin atmosphere contained nitrogen, we’ve already learned that the gas is escaping Pluto’s atmosphere much faster than expected.