Pioneer 10 was the first human-made object to pass the orbit of Neptune (which at the time was further out than Pluto), leaving behind the last planet in the Solar System, and headed toward Aldebaran in Taurus, which it would reach in another 2 million years. Pioneer 10’s last signal arrived on January 22, 2003, when it was 12 billion kilometers from the Sun, or 80 AU: after thirty years, its plutonium generators were exhausted.
