After months, and for some people decades, the first image from NASA's new space telescope, the James Webb Space Telescope, has taken its first, focused, image.
The James Webb Space telescope has a mirror that is 6.5 metres wide, much bigger than the Hubble Space Telescope's mirror of 2.4 metres. When the Hubble Space Telescope was built, it was designed to fit inside the Space Shuttle, which could fit a telescope with a mirror 2.4 metres wide. Any bigger and it would not have fit.
However, not only is the Space Shuttle retired (and it wouldn't fit anyway), but there really is no rocket big enough to fit something that size.
The James Webb went up on an Ariane 5 rocket, which can fit objects up to 4.57 metres wide. As this was always going to be a problem, NASA built a telescope that could be folded to fit. The mirror itself was folded to fit inside, and once it was launched, it had to start a process over the next few weeks of slowly unfolding in space.
That wasn't the end of it though. The mirror is actually made up of 18 smaller segments, like a honeycomb. This meant this bigger mirror was not just folded into a few sections to fit, but each of these smaller segments moved around as well.
Getting these mirrors into the right alignment has been the majority of work of the James Webb since arriving at its destination. The James Webb Space Telescope is at Lagrange Point 2 or L2, a spot where the gravitational force or pull of two objects, in this case the sun and Earth, is even, meaning you can nominally keep a spacecraft nearly parked in a spot.
It also has the advantage of being far away from the Earth, meaning the Earth doesn't interfere as much. L2 is about 1.5 million kilometres away from Earth, much further than the 540 kilometre orbit of the Hubble Space Telescope.
For the past couple of months, these mirrors have been slowly adjusted, to not only just fit in with the other honeycomb like segments, but get it into the right spot to produce a focus, clear image. The mirrors have to be in position within an accuracy of a few nanometers, that is a billionth of a metre precision.
Seeing this beautiful star is the result of lots of hard work. The star itself is not only beautiful and clear, but you can see the bright lines coming out. This is not a real feature of the star, but one we often seen. Telescopes like the James Webb have a secondary mirror, that focuses the light from the huge mirror. This secondary mirror sits above the main mirror, and in order to be supported, there are structures holding it up. Bright stars can sometimes reflect off of these support structures, creating this feature.
There are also all the galaxies in the background of this image, this is truly amazing, being seen in detail that we only dreamed of. Compared to previous images, it is like upgrading your TV from 1080p to 4k.
A new view of the universe is opening up.
- Brad Tucker is an astrophysicist and cosmologist at Mount Stromlo Observatory, and the National Centre for the Public Awareness of Science at ANU
