About 4,000 astronomers from all over the world have used the telescope to probe the universe. Astronomers using Hubble data have published nearly 7,000 scientific papers, making it one of the most productive scientific instruments ever built.

The telescope's observations have produced more than 30 terabytes of data, equal to about 25 percent of the information stored in the Library of Congress.

During its lifetime Hubble has made about 800,000 observations and snapped about 500,000 images of more than 25,000 celestial objects.

Hubble does not travel to stars, planets and galaxies. It snaps pictures of them as it whirls around Earth at 17,500 mph. The telescope has made just more than 100,000 trips around our planet, racking up about 2.4 billion miles. That mileage is slightly more than a round-trip between Earth and Saturn.

Among Hubble's greatest discoveries are determining the age of the universe (13.7 billion years), finding that virtually all major galaxies have black holes at their center, discovering that the process of planetary formation is relatively common, detecting first ever organic molecule in the atmosphere of a planet orbiting another star, and providing evidence that the speed at which the universe is expanding is accelerating -- caused by an unknown force that makes up more than 75 percent of the universe.

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Editor:Yang Jie