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KATHERINE COLE: The Hubble Space Telescope continues to make valuable discoveries after more than twenty years in orbit around Earth. Hubble recently showed a fourth moon orbiting Pluto. Astronomers temporarily named it P4. The moon is the smallest to be discovered around the icy dwarf planet.

Pluto's new moon, P4

Astronomers estimate that the moon is from thirteen to thirty-four kilometers across. They first saw it in a Hubble photo taken on June twenty-eighth.

The American space agency launched the Hubble Space Telescope in nineteen ninety. Reaching that day took years of work. Ed Weiler is the space agency’s chief astronomer.

ED WEILER: “The Hubble, when it was launched, represented an increase in capability of other telescopes on the ground by a factor of ten. The last time in human history in astronomy that we leaped a factor of ten, in one step, was when Galileo stopped using his eye and put the first telescope to his eye.”

JIM TEDDER: Nancy Grace Roman was the space agency's first chief of astronomy. She led the effort that led to the creation of the Hubble Space Telescope.

NANCY GRACE ROMAN: “Astronomers had been wanting to get observations from above the atmosphere for a long time. Looking through the atmosphere is somewhat like looking through a piece of old, stained glass. The glass has defects in it, so the image is blurred from that.”