The enormous questions guiding astronomy are no bigger than how the first stars and galaxies formed and ultimately revealed our own existence. The solutions lurk in the depths of the Universe, so distant that light from the first galaxies in formation would have to travel billions of years to reach us. Just 200 million years after the Big Bang, this early period is beyond the already surprising limits of earlier telescopes. It is currently visible through the James Webb Space Telescope.
However, even the best space telescope is only as good as the instruments it is attached to. This is where the NIRSpec instrument, one of Europe's contributions to the Webb Space Telescope, comes into play.
“Every device design begins with the wishes of scientists. According to Pierre Ferruit, a former Webb Project Scientist at ESA, NIRSpec was largely shaped by research into the origins of the first stars and galaxies.
Webb's Near Infrared Spectrograph is known as NIRSpec. Its job is to split the infrared light Webb captured into individual wavelengths to create a spectrum. Astronomers can learn a lot about an object's physical properties and chemical makeup by observing how its brightness changes over a range of wavelengths. Before Webb and NIRSpec, this was unthinkable for these most distant galaxies.
“Now that we can do this, a whole new path opens up before us. According to ESA astronomer Giovanna Giardino, we can now study distant galaxies in the same way that we study objects near us.
This information will allow scientists to trace the evolution of galaxies from the beginning of the universe to what we see today.
NIRSpec was created under the management of ESA with Airbus Defense and Space Germany serving as prime contractor. Seventy people were brought together by Airbus in Toulouse, France, Ottobrunn and Friedrichshafen, Germany. They also received help from NASA and 17 European subcontractors.
The team concluded from the start that keeping things simple was the best strategy for success. According to Ralf Ehrenwinkler, Head of the NIRSpec Program at Airbus, “When you look at the design of NIRSpec, it's pretty simple.”
By keeping the device's light guidance system simple, the team was able to focus on the device's breakthrough features. The most important of these was the need to effectively record the spectra of a large number of objects simultaneously, something that has never been done in space before.
The urge to explore the distant Universe, where galaxies are so faint, directly required this special skill. We would have to observe thousands of them to get a complete picture of our interactions with them.
Thanks to the historic Hubble Deep Field, we were able to see this universe for the first time in 1995. Starting on December 18, Hubble looked at a single region of the sky for ten days and took advantage of the unobstructed perspective of the universe. The selected area was just a microscopic point, making up about one millionth of the entire sky. But Hubble has found more than 3000 previously undiscovered objects, mostly baby galaxies billions of light-years away.
Thanks to Webb's massive 6,5-metre mirror, similar deep-field photos can now be taken in hours instead of days, and NIRSpec can capture their spectra. However, it would be absolutely impractical for NIRSpec to be able to get only one spectrum at a time, as there are so many galaxies to record.
Therefore, the group needed to figure out how to handle a large number of items at once. They have had incredible success.
The ability to collect spectrum for up to 200 objects simultaneously is game-changing, according to Maurice Te Plate, an engineer working on ESA's NIRSpec systems.
NIRSpecuses a revolutionary tool called the micro-shutter array to accomplish this amazing multitasking feat. It consists of about a quarter of a million small, autonomous shutters and is supplied by NASA's Goddard Space Flight Center in Greenbelt, Maryland, USA. Each is only 80 by 180 micrometers in size. Each of them can be given a command to open and close when desired.
This solves one of the main problems with obtaining spectra from the far reaches of the Universe: if the spectra of closer objects, such as the spectra of stars and less distant galaxies, are not obscured, the fainter ones will interfere with their spectra.
“All others are closed; we leave open only those above interesting objects. As a result, only light emitted from selected targets enters the spectrograph optics for analysis, according to Maurice.