James Webb Space Telesope is now chilling at -266°C, shy of lowest temperature possible

The James Webb Space Telescope has reached its operational temperature, which is just a little more than what matter can possibly reach. Webb's MIRI instrument has attained minus 266 degrees Celsius while it awaits complete awakening at the second Lagrange point- its current location. NASA revealed that the engineers aligning Webb used the cryocooler, the cooling device for MIRI, and the telescope is now operating at 6.4 kelvins, just shy of absolute zero (kelvin) or −273.15 °C.

Webb has three other major instruments- the Near-Infrared Camera (NIRCam), Near-Infrared Spectrograph (NIRSpec), and Fine Guidance Sensor/Near InfraRed Imager and Slitless Spectrograph (FGS/NIRISS) that it will use when fully operational.

Why does MIRI have to be so cold?

Webb's MIRI, and other three instruments for that matter, need to operate at extremely low temperatures because they have been designed to detect infrared light. Infrared light are those which have a wavelength slightly longer than those that human eyes can see- like sunlight.

It has been known that hidden planets, stars and even galaxies emit infrared light but so do Webb's instruments through the heat of their electronics and optics hardware. To ensure that the instruments do not pick each other's heat and mixup the infrared light from actual cosmic objects, they have been cooled down to such low temperatures. As for MIRI, it needs to be coldest because it detects longer infrared wavelengths than the other three instruments.

NASA mentioned another reason for MIRI's low temperature and that is to suppress 'dark current'. Dark current or electric current is created by the vibration of atoms in the detectors of Webb's instruments and they can mimic a true signal in the detectors. These signals can give the false impression that the detectors have been hit by light from planets or stars and drown out the real signals astronomers are looking for. Thus, they to be eliminated.

The Webb telescope, which was launched on December 25 is just weeks away from starting its observations. Data from Webb would be complemented with that of the Hubble Space Telescope to make unprecedented discoveries of our universe. 

Image: Twitter/@NASAExoplanets