In December, NASA is scheduled to launch the huge $10 billion James Webb Space Telescope, which is sometimes billed as the successor to the aging Hubble Space Telescope. NPR correspondents Rhitu Chatterjee and Nell Greenfieldboyce talk about this powerful new instrument and why building it took two decades. For more of Nell's reporting on the telescope, check out "NASA Is Launching A New Telescope That Could Offer Some Cosmic Eye Candy." (https://www.npr.org/2021/09/16/1036600340/nasa-is-launching-a-new-telescope-that-could-offer-some-cosmic-eye-candy)You can follow Rhitu on Twitter @RhituC and Nell @Nell_Sci_NPR. Email Short Wave at ShortWave@NPR.org.