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New Horizons makes historic flyby of Pluto

Paul Sutherland, Feature writer
Jul 14, 2015, 17:35 UTC, Updated Jul 14, 2015, 22:31 UTC

Sen—NASA's New Horizons probe reached the climax of its nine-year, five billion km journey today when it made its closest approach to Pluto, racing past the dwarf planet and through its system of five moons.

The spacecraft was little more than 12,500 km from Pluto's surface at 11.49 UTC before shooting away again at a speed of nearly 14 km (8.7 miles) per second.

As the mission team cheered the moment, NASA released the latest incredible image taken of Pluto, showing its bright heart-shaped feature and other landmarks in unprecedented detail.

New Horizons has already been sending back increasingly clear pictures of Pluto and its largest moon, Charon, in the days before the flyby. But the images it is taking today will show features on these worlds' landscapes as never before. As he prepared for New Horizons' big moment yesterday, the mission's principal investigator Alan Stern told Sen: "Pluto is simply amazing!"


Cheers from the New Horizons team at mission control as they see the latest image from the probe. Image credit: NASA/Bill Ingalls

NASA Administrator Charles Bolden said in a statement: "The exploration of Pluto and its moons by New Horizons represents the capstone event to 50 years of planetary exploration by NASA and the United States. Once again we have achieved a historic first. The United States is the first nation to reach Pluto, and with this mission has completed the initial survey of our Solar System, a remarkable accomplishment that no other nation can match."

Excited followers of the mission will need to be patient as they wait to see today's glorious close-up views from the flyby for themselves. New Horizons is focusing all its efforts on gathering data today, and this will only be radioed back to Earth after the encounter. First pictures are expected tomorrow, Wednesday July 15. The craft's instruments will be swivelling to gather pictures and take other measurements of Pluto, Charon, and the other four, much smaller satellites, Styx, Nix, Kerberos, and Hydra.


A diagram showing how New Horizons will fly through the Pluto system. Image credit:NASA-JHUAPL-SWRI

During the flyby and the rest of today, events can be followed on NASA TV. Special coverage of the flyby, with the release of the last image received before it began, started at 11.30 UTC (7.30am EDT) and continues until 13.00 UTC (9am EDT).

Then from 00.30 UTC tomorrow (8.30pm EDT tonight) a special programme, Phone Home, will be broadcast from Mission Control at Johns Hopkins Applied Physics Laboratory in Maryland. It will include a preprogrammed signal that New Horizons is due to transmit after its closest approach. The space probe is so distant that this signal, travelling at the speed of light, will not be received until about 13.02 UTC tomorrow (9.02pm EDT tonight).


Pluto and Charon imaged on July 11. Color from the probe's Ralph instrument has been added to the black-and-white LORRI images. Image credit: NASA-JHUAPL-SWRI

Before the flyby, New Horizons has already answered one long-standing riddle over Pluto—just how big it is. From images captured by its Long Range Reconnaissance Imager (LORRI), mission scientists found that the dwarf planet is 2,370 km (1,473 miles) in diameter, which is somewhat larger than previous estimates. The result suggests that Pluto is bigger than all other objects known in the Solar System beyond Neptune, including rival Eris in the Kuiper Belt.

The images also allowed the team to get a fix on Charon's size, confirming it to be 1,208 km (751 miles) wide. Two other satellites, Nix and Hydra, which were only discovered using the Hubble Space Telescope in 2005, are about 35 km (20 miles) and 45 km (30 miles) across, respectively. The sizes of the smallest moons, Kerberos and Styx, are still not clear.