NASA is preparing to launch its best space telescope yet, and it will gaze at the stars through a golden mirror.
It’s not a single piece, but an array of 18 segments made of beryllium — a rare metal that is both strong and light — and coated with a microscopically thin layer of pure gold for maximum reflectivity.
Expected to launch in 2020, the James Webb Space Telescope spans a whopping 21 feet (6.5 meters) across and cost $8.8 billion.
Each of the mirror’s 18 segments weighs 46 pounds (20 kilos) and spans 4.3 feet (1.3 meters), forming an array that will dwarf Hubble’s 7.9-ft primary mirror.
And a larger mirror means better performance.
But, to make it fit into the rocket that will send it into space, the mirror needed to be folded, which explains why it’s made of hexagons.
... each one needs to be aligned to 1/10,000th the thickness of a human hair. What’s even more amazing is that the engineers and scientists working on the Webb telescope literally had to invent how to do this.
Optical Telescope Element Manager for the James Webb Space Telescope at NASA
Once in space, getting these mirrors to focus correctly on faraway galaxies will be a challenge.
The Webb is designed to be a more capable successor to the Hubble Space Telescope, launched in 1990.
While Hubble orbits the Earth at about 340 miles of altitude, Webb will be sent almost a million miles into space, at a specific location called “L2.”
It’s very cold out there, which is oddly what NASA wants.
The telescope will be able to see deeper into space by looking at the universe not through visible light, but through infrared radiation, which we normally think of as heat.
That means that the mirror itself needs to be super cold, to avoid emitting any heat that could interfere with its own observations.
The James Webb telescope, was named after the NASA administrator who oversaw the birth of the Apollo program in the 1960s.
It was announced in 1996, and a full-size model has been on a world tour that has touched over a dozen cities, building anticipation in the general public.