NASA has marked the silver anniversary of the Hubble Space Telescope with fireworks of a celestial kind, conveyed by the orbiting observatory itself.
To commemorate Hubble's launch on 24 April 1990, NASA has released images - including a three-dimensional visualisation in video form - of the Westerlund 2 cluster, located about 20,000 light-years away in the constellation Carina.
"This is really an exciting week for astronomers and people who love astronomy all over the world," Hubble scientist Jennifer Wiseman said during an anniversary celebration in Washington, DC.
From its orbital perch 547 kilometres above Earth, Hubble's sharp eye can distinguish individual stars in the cluster, which is teeming with about 3000 newborns.
With its infrared vision, Hubble also can peep inside cocoons of dust and gas where even more stars are forming.
Learning about the lifecycle of stars was one of the reasons Hubble was built.
By operating above distortions and blocking effects of Earth's atmosphere, astronomers hoped to look farther back in time, at generations of stars and galaxies that formed closer to the Big Bang, some 13.7 billion years ago.
NASA administrator and former astronaut Charlie Bolden, who was the pilot on the mission that launched Hubble, said he "never thought it would last this long".
Many of the telescope's most important discoveries turned out to be in areas that did not even exist when it was launched.
Hubble's observations of a particular kind of exploded star helped astronomers realise that the pace of the universe's expansion is ramping up, propelled by some unknown force referred to as "dark energy".
Hubble also has imaged a planet beyond the solar system and scanned other planets' atmospheres for telltale chemical fingerprints. The first so-called exoplanet was discovered in 1992, two years after Hubble's launch.
"Hubble has fundamentally changed our human understanding of our universe," Mr Bolden said.
NASA hopes to keep Hubble operating through 2020 to overlap with its infrared successor, the James Webb Space Telescope, due to launch in October 2018.
- REUTERS