While celebrating 25 years of the Hubble Space Telescope and its discoveries, NASA says it is moving forward with work on its successor, a powerful instrument designed to gaze even more deeply into the universe and farther back in time.

The James Webb Space Telescope, on track for an October 2018 launch, will be around 100 times as powerful as Hubble, the space agency says, due in large part to a larger mirror than has ever gone into space before.

The Hubble telescope, with its 7.9-foot diameter light-collecting mirror, was a state-of-the-art astronomical instrument when it was created in the 1970s.

The James Webb telescope, when it is launched, will unfold its mirror to an impressive 21 feet across.

Using that massive light collector, it should provide a glimpse back in time to when the first stars and galaxies began to form in a young universe.

"JWST will be able to see back to about 200 million years after the Big Bang," NASA said on its website, serving as a "powerful time machine with infrared vision that will peer back over 13.5 billion years to see the first stars and galaxies forming out of the darkness of the early universe."

By using infrared light, which the human eye cannot see but which can be sensed as heat, the Webb instrument will be able to see deep into the universe despite any obscuring dust, providing direct observations of cosmic targets of interest to astronomers and cosmologists.

"What the Webb will really be doing is looking at the first galaxies of the universe," says Mark Clampin, Webb project scientist at the space agency's Goddard Space Flight Center in Maryland.

"We will also be able, with these capabilities, to look in very dark parts of the universe where stars are being born."

A joint project of NASA, the European Space Agency and the Canadian Space Agency, the James Webb Space Telescope, although still three years away from launch, is being eagerly awaited by astronomers around the world.

"JWST can make a huge contribution," said astronomer Rupali Chandar of the University of Toledo, who is attending a Hubble 2020 symposium this week in Baltimore.

With its all-seeing infrared eyes, the Webb telescope can peer closely into nearby galaxy clusters as well as those dating back to the earliest infancy of the universe, she said.

It is expected to continue the dramatic successes of the Hubble telescope, says Matt Greenhouse, a researcher working on the telescope's science instruments.

"Just as Hubble rewrote all the textbooks, Webb will rewrite it again," he says.