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  • BBC Sky at Night

    BULLETIN

    Apr 21, 2022 5 minutes

    JWST focused on the job ahead

    The space telescope is nearly ready to begin scanning the infrared Universe

    After weeks of alignment, NASA finished focusing the primary mirror of the James Webb Space Telescope (JWST) on 11 March, achieving a precision that exceeds the original goal.

    The milestone marks the end of a procedure known as ‘fine phasing’. JWST’s main mirror is made up of 18 hexagonal segments; to focus these the team pointed the telescope at a lonely star chosen to be easily identified, with few nearby companions. They then adjusted each panel so that when combined, the 18 separate images were aligned into a single point of light, focused to within an accuracy of 50 nanometres – a fraction of the wavelengths of infrared light it will observe in.

    Next, the team imaged the star with

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