Voyager 1 logs yet another milestone in space history August 17 when it crosses an invisible boundary that marks 100 astronomical units (AU) from the Sun — about 15 billion kilometers (9.3 billion miles) out there — farther away than any human-made object has ever gone in space.
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One AU is approximately the mean distance between the Earth and the Sun or about 93 million miles.
Together, Voyager 1 and Voyager 2 — twin probes launched on September 5, 1977 and August 20, 1977 — represent the most successful planetary exploration mission of all time.