FTT World
Nov 19, 20225 min
Astronomy is motivated by great questions, and none are bigger than how the first stars and galaxies formed, eventually giving rise to our own existence. The answers are buried in a faraway cosmos, so far away that light traveled billions of years to reach us, delivering images of the earliest galaxies forming. This early epoch, only 200 million years after the Big Bang, is beyond the reach of prior telescopes, which were already amazing. It is currently visible thanks to the NASA/ESA/CSA James Webb Space Telescope. Even the best space telescope is only as good as the instruments attached to it, which is where the NIRSpec instrument, one of Europe's contributions to the Webb project, comes in.
According to Pierre Ferruit, former ESA Webb Project Scientist, the ambition of the scientists comes first in any instrument design. NIRSpec was formed by studying the development of the earliest stars and galaxies.
Webb's Near-Infrared Spectrograph is abbreviated as NIRSpec. Its duty is to separate the infrared light captured by Webb into its constituent wavelengths in order to create a spectrum. Astronomers may learn a lot about an object's physical features and chemical makeup by observing how its brightness fluctuates across different wavelengths. This was difficult to achieve before Webb and NIRSpec for the most distant galaxies.
According to ESA astronomer Giovanna Giardino, "now that we can accomplish this, a tremendous avenue is opening up for us." We can now examine distant galaxies, in the same manner, we study nearby things.
The data will allow scientists to trace the evolution of galaxies from the very early phases of the universe to the things we see around us today. NIRSpec has evolved under the direction of ESA, with Airbus Defense and Space Germany serving as the main contractor. Airbus organized a team of seventy workers from its Ottobrunn and Friedrichshafen, Germany, and Toulouse, France, facilities. They were also helped by NASA and 17 European subcontractors. Early on, the team determined that the best approach to achieve success was to simplify everything.
According to Ralf Ehrenwinkler, Head of the NIRSpec Program at Airbus, the design of NIRSpec is rather straightforward.
By keeping things basic in terms of how light is channeled through the instrument, the team was able to focus on the groundbreaking elements of the instrument. Among these was the requirement to efficiently record spectra from several objects at the same time, which had never been done in space previously. The ambition to investigate the far cosmos, where galaxies are so faint, immediately demanded this one-of-a-kind capacity. To piece together a complete picture of our early origins, we would need to witness thousands of them.
The iconic Hubble Deep Field provided our first sight of this area in 1995. Hubble took advantage of its unobstructed vision of the universe by staring at a single area of sky for 10 days starting on December 18. The chosen spot was hardly larger than a speck, around one-fourth of the size of the entire sky. Nonetheless, Hubble discovered over 3000 previously unknown objects, the majority of which were infant galaxies billions of light-years away. Similar deep-field photos may now be collected in hours rather than days, thanks to Webb's enormous 6.5-meter mirror, and NIRSpec can capture their spectra. However, with so many galaxies to record, it would be absolutely unworkable if NIRSpec could only acquire one spectrum at a time. So the team had to figure out how to accomplish it for several items at the same time. They were a huge success.
According to Maurice Te Plate, ESA's NIRSpec Systems Engineer, "we're able to gather spectra for up to 200 objects at a moment, it's a game changer."
NIRSpec employs a revolutionary gadget known as a micro-shutter array to accomplish this astounding feat of multitasking. It is made and provided by NASA's Goddard Space Flight Center in Greenbelt, Maryland, USA, and is made up of around a quarter million small autonomous shutters. Each one measures only 80 by 180 micrometers. They may be operated independently to open and close as needed.
This tackles one of the most difficult challenges in obtaining spectra from the far universe: if the spectra of nearby objects, stars, and less distant galaxies are not masked, they interfere with the fainter ones.
According to Maurice, we only leave the ones that are over fascinating items open, while the others are all closed. As a result, only light from the specified targets enters the spectrograph optics to be evaluated.
NIRSpec is meant to look at celestial objects considerably closer to home, such as exoplanets, as well as the distant universe. The atmospheres of these worlds absorb part of the infrared light that flows through them from their parent star. NIRSpec searches for the minuscule quantities of light that are absent at certain wavelengths by gathering the star's radiation and separating it into a spectrum. They can then determine which compounds are present in the planet's atmosphere and extract more information about physical conditions.
According to Giovanna, "we can now observe the signatures of several critical chemicals in the atmospheres of exoplanets that were not visible from the ground or with space instruments prior to NIRSpec."
NIRSpec expands astronomers' skills. It may, for example, break bigger objects like galaxies and nebulae into 30 slices and detect a spectrum for each slice in a single shot. The resultant maps of physical circumstances and chemistry are critical to understanding the birth and death of stars, as well as the operation of galaxies.
To work in the near-infrared, NIRSpec and much of Webb must operate at a temperature of 40 Kelvin (-233°C), which is maintained by Webb's characteristic sun cover. When it comes to developing exact scientific instruments, this creates a significant obstacle. When cooled, different materials shrink at varying rates, causing minor distortions in the instrument that impact its accuracy.
According to Ralf, this was the most difficult aspect, which is why Airbus opted to manufacture this instrument mostly out of silicon carbide. Silicon carbide is used for the base plate, the majority of the structures, and the mirrors.
Silicon carbide is a ceramic substance that is exceptionally stable at low temperatures while being difficult to deal with. Thermal distortions might be minimized by creating the majority of the instrument out of it. However, it necessitated being totally confident of the design before beginning production. NIRSpec originated as a block of silicon carbide in the so-called green state, which is soft and workable. NIRSpec was then machined into shape in the same manner that a sculptor shapes stone. All of the holes and channels were drilled, and once completed, it was placed in a furnace to be "sintered." This hardens the material and makes it incredibly difficult to manufacture. As a result, the team had to be absolutely convinced of the design before beginning production.
Working in silicon carbide was a challenge, according to Maurice, and I'm quite happy that we were able to complete it.
Working with the material has now become something of a European specialty, thanks in part to their success. The success of NIRSpec was brought home to the crew when the first photographs and data were returned to Earth.
Ralf stated, "I'm an engineer, not a scientist." So I'm relieved to see that all of the telemetries is green and NIRSpec is operational. But I will say that when the initial photographs were released, I was in Baltimore with around 200 other individuals. We were all overcome with emotion.
And now that the evidence is pouring in, many others are feeling the same way.
Pierre stated, "I am astounded by the quality of the spectra that we are obtaining." I can tell that the observers are pleased with the data as well. That, in my opinion, is why we created NIRSpec. I believe this is shared by the entire crew. It feels amazing now that NIRSpec is delivering.
Once the painstaking data analyses are completed, we will have new answers to those extraordinary questions that are so important to understanding our own existence: how the first galaxies and stars formed in our universe, and how frequently planets orbiting other stars offer conditions conducive to life as we know it. It is exactly what NIRSpec was designed to do: provide multiple windows to examine huge topics.