On this day, 39 years ago, March 6, 1986 (January 26, 1986, the spacecraft sent back photos of Halley's comet. Halley's comet appears once in 76 years. On March 6, 1986, the Soviet spacecraft "Vega-1" flew within 5500 miles of Halley's comet and sent back the first batch of photos of the comet's ice core. The spacecraft, operating on ground orders, pointed several cameras at the comet, gradually approached, and transmitted about 500 television images over three hours. Scientists from the United States and many other countries were invited to Moscow to watch for themselves the encounter between Vega-1 and Halley's comet, which returns to Earth only once every 76 years. Prediction data from spacecraft and scientific instruments indicate that the comet's core is made of ice and is about 3 miles across, and that the sun's heat causes the comet to melt and release gas so we can see that the comet has a tail. In fact, this tail is two to three times larger than previously thought.