Pioneer 10 was the first spacecraft ever to cross the asteroid belt. Before this, astronomers did not have a clear idea whether the density of tiny asteroids in the belt would be too great for a ship to go through it without being smashed. (The nearest Pioneer 10 came to a known asteroid was 5.5 million miles [8.8 million kilometers].) In 1973 Pioneer 10 flew by Jupiter and took the first close-up pictures of the largest planet in our solar system. It then kept traveling, crossed the orbits of Neptune and Pluto, and left the major planet region of the solar system in 1983. The last successful contact with Pioneer 10 was made on January 23, 2003. At its current rate and direction of travel, it will reach the star Aldebaran in the constellation Orion in about two million years.