When NASA announced in 2004 that it was canceling a final mission to repair the then-ailing Hubble Space Telescope — effectively a death sentence — the agency received a letter from a 9-year-old girl who wanted to donate her lunch money to save Hubble. That letter, among countless others, exemplifies the public’s love affair with the observatory, which turns 20 years old this month.
Since its launch on April 24, 1990, Hubble has repeatedly risen from the ashes to produce pictures of unparalleled clarity and beauty. The observatory has recorded nearly a million images and spectra in about 110,000 trips around the Earth. Among its cosmic postcards — some of the best in the pages to follow — Hubble has caught bruises left on Jupiter by fragments of a comet, elderly stars gift-wrapped in shells of glowing gas, the slender arms of spiral galaxies and nebulae ablaze with the light of newborn stars.
Not bad for a telescope initially dubbed a techno-turkey for its flawed primary mirror. Soon after astronauts fixed that problem during a series of space walks in late 1993, Hubble began living up to its promise as the first major visible-light telescope to fly above Earth’s image-distorting atmosphere. The telescope has several times rewritten the textbooks on astronomy. Perhaps most dramatically, Hubble’s study of remote stellar explosions (inset) provided key evidence for an acceleration in the rate of cosmic expansion, leading scientists to surmise the existence of dark energy. Hubble also delivered compelling confirmation that the universe has evolved in a way predicted by the Big Bang theory. Closer to home, Hubble recorded one of the first images of a planet beyond the solar system.
Yet for all of Hubble’s scientific breakthroughs, the beauty of its images ranks high among its most lauded achievements. Hubble’s pictures hang in museums, adorn album covers and have appeared in major motion pictures. Its online image gallery receives about 200 million hits a month.Last May, astronauts did indeed perform a final servicing mission, transforming Hubble into a spanking new observatory that has become the ultimate galactic time machine. Hubble’s new infrared camera has already spotted galaxies believed to be the most distant ever recorded. Because peering deep into space is the same as peering far back in time, the pictures reveal what the galaxies looked like just a few hundred million years after the Big Bang. If the servicing mission was an early birthday present from Earth, then Hubble has more than returned the favor. Taking us back to our cosmic beginnings may be the observatory’s ultimate gift.