Mark Megahan
Not just cool, but amazingly super-frigid. The coldest temperature on record here at the surface of Earth is -128.6 degrees Fahrenheit. That’s where the mercury dropped to on July 21, 1983 in Vostok Station, Antarctica. To our newest remote telescope, even that chilly freeze is too blazing hot to function. Late NASA administrator James Webb would be proud to know his namesake telescope is the “coolest” thing in space.
Deep space precision
The James Webb Space Telescope was launched on Christmas Day 2021. As a replacement for the retiring Hubble, Webb will gaze out on “the formation of the most distant galaxies and exoplanets.” To do that requires ultra-fine precision adjustments to the special gold plated mirror array. All the other instruments on board are just as touchy. Webb specializes in the infrared part of the spectrum.
Carefully crafted detectors inside each of the Webb Space Telescope’s modules “convert infrared heat signals into electrical signals.” Those signals are then “processed to generate the images astronomers see here on Earth.” Because what the gear is observing falls in the “heat” range of the light spectrum, any heat generated by the hardware itself has to be removed. As the experts explain “because its own hardware produces infrared heat energy, any data gathered becomes useless if that energy isn’t suppressed.”
Shadowy places in space are really cold to start with, but not cold enough for Webb. In order to cancel out the heat the equipment produces on it’s own, more refrigeration is needed. It’s not your typical air conditioner. Webb is fully equipped with “an electrically-powered cryogenic cooler.” One of the reasons why there haven’t been any official photos released yet is because Webb is still “chillin.'”
Unimaginably cold
Webb won’t be happy until it’s onboard Mid-Infrared Instrument cools down to a nippy final temperature of 6.4 kelvin. It hit the magic number April 7. To put that in perspective, zero kelvin is absolute zero where “all atomic motion is suppressed.” 6.4 kelvin works out to around -448.15 degrees Fahrenheit. Even the emptiest parts of deep space only get a little colder. Natural temperatures go as low as -455 degrees Fahrenheit.
The equipment has to be that cold in order for the MIRI camera and spectrograph to work accurately. Designers are convinced the minuscule energy differences detected will reveal “the infrared light of distant galaxies, young stars, faint comets, and objects in the Kuiper Belt” Those are the ones like former “planet” Pluto which hang out in space beyond the orbit of Neptune.
By parking the James Webb Space Telescope a good million miles away from Earth, the team avoids the sun’s light and heat. Because they want to look at the big bang itself, if they can, they shade the telescope with a “five-layer, tennis-court sized sunshield.” Using such passive cooling techniques gets the gear down to -396.67 degrees Fahrenheit. To make sure the telescope is really cold enough, they measure “atom vibration speed.” When the atoms stop moving, they can start working.
