WASHINGTON — NASA reports that its record-breaking space probe, the New Horizons, has reached another impressive milestone. <br /><br />On 17 April the half-ton craft became only the fifth man-made machine to fly more than 50 astronomical units into deep space. <br /><br />That's 50 times the distance from Earth to the Sun, for a total of 7.5 billion kilometers from Earth. <br /><br />At that distance, it takes commands sent from Earth at the speed of light, a whopping 7 hours to reach the probe; and scientists have to wait another seven hours to hear if the probe received the commands. <br /><br />Launched in 2006, the New Horizons is much newer than Earth's other deep-space probes, the two Voyager and two Pioneer spacecraft launched between 1972 and 1977. <br /><br />At a travelling speed of 58,000 kilometers per hour, it is also the fastest machine ever made. <br /><br />New Horizons became the first probe to study the distant planet of Pluto, and the first to study objects in the Kuiper Belt — a huge disk of mostly ice chunks that ring the outer reaches of our solar system. <br /><br />It also filmed the first video of an off-Earth volcano when it flew by Jupiter's moon, Io.
