Attempts to spot the oldest visible objects in the universe have taken an important step forward this week. An instrument that should make it possible to isolate “first light” has been completed and is ready for the James Webb Space Telescope.
The telescope is scheduled for a 2018 launch and is designed to sense images deeper in space (and thus further back in time) than the Hubble telescope. James Webb is a joint project of US, Canadian and European space organizations, with the four main instruments produced on both sides of the Atlantic.
One of the instruments, the Mid-Infrared Instrument (Miri) is now complete and has passed initial testing in the UK, meaning it’s ready to be shipped to Maryland.
It’s made up of three parts: a camera, a coronograph (which will block light from brighter objects to make it easy to see dimmer ones) and a spectograph (which breaks the lights up into different colors.)
Miri will need to be kept at minus 266 degrees Celsius (7 degrees Kelvin) so that it can detect faint infrared light. That means it will require a dedicated cooling mechanism using a flow of helium, separate to the main cooling system used on the telescope. As part of testing, Miri was cooled to those temperatures as well as put in a vacuum chamber.
By detecting light at infrared wavelengths (which are invisible to the human eye), the telescope is expected to be able to detect light from more than 13 billion years ago. The aim is to spot the first generation of stars that emitted light.
The James Webb Space Telescope has proved politically controversial thanks to delays and budget-busting cost increases. There was discussion of abandoning the project completely last year, but it was permitted to go ahead with tight constraints on further spending.
The current plan is to launch the telescope from French Guiana at the main spaceport of the European Space Agency. It will then be sent 1.5 million miles to Lagrangian point L2. That’s the point in space where an object can orbit the Sun in synch with the Earth. This not only minimizes the effects of shadow blocking the view, but also means the telescope can operate with a single radiation shield (albeit the size of a tennis court.)
(Image credit: Science and Technology Facilities Council, European Space Agency)