The twin Voyager spacecraft, launched in 1977, continue to speed away from Earth at a rate of over 17 km/s (about 38,000 mph). At a distance of almost 125 AU (about 10 billion miles) Voyager 1 is the furthest man-made object and still going!
In-situ measurements suggest
that Voyager 1 has recently passed through the heliopause, the boundary between space connected to the Sun and the interstellar medium, Professor Merav Opher
(a coauthor on the above linked paper) and her research group are actively investigating this boundary, making use of both the Voyager data-set and modelling.
(Image Courtesy NASA.)