WASHINGTON - The James Webb space telescope has taken its first image of an exoplanet - a planet outside our solar system - as astronomers hail the device's performance since its launch last year.

Images from the most powerful space telescope ever built have thrilled observers as it orbits the Sun 1.6 million km from Earth.

Its latest pioneering pictures show the exoplanet, called HIP 65426 b, is a gas giant with no rocky surface and could not be habitable. "This is a transformative moment, not only for Webb but also for astronomy generally," said astronomy professor Sasha Hinkley at the University of Exeter, who led the observation team.

Webb's infrared gaze and coronagraphs - telescopic attachments that block out starlight - enable it to take direct images of exoplanets. "It was really impressive how well the Webb coronagraphs worked to suppress the light of the host star," Prof Hinkley said in a Nasa statement on Thursday.

The HIP 65426 b exoplanet is six to 12 times the mass of Jupiter and young - about 15 million to 20 million years old, compared with the 4.5-billion-year-old Earth.

The telescope, which released its first images only in July, has already revealed dazzling new details of the Phantom Galaxy and of the planet Jupiter.

The Hubble space telescope previously captured direct exoplanet images, but in far less detail. "I think what's most exciting is we've only just begun," said University of California astronomer Aarynn Carter. "We may even discover previously unknown planets."

The US$10 billion (S$14 billion) Webb telescope is a collaboration between Nasa, the European Space Agency and the Canadian Space Agency.

It is expected to operate for approximately 20 years.

AFP