Breaking news! NASA official announcement: Webb will use spectroscopy to study the composition of distant galaxies

Credit image: NASA
Credit image: NASA

Article by: Andacs Robert Eugen, on 10 March 2022, at 11:32 am Los Angeles time

Breaking news - NASA official announcement: Webb Will Use Spectroscopy to Study Composition of Distant Galaxies. 

NASA recently claimed that the team who lead Webb made great strides this week in aligning the telescope's NIRCam instrument. NASA is working hard to align the telescope's mirrors so that when Webb catches something, it won't show up in the picture, the same thing 18 times (the number of telescope mirrors, each taking a picture), Webb sees the object, only one.

NASA is currently taking data to understand the optical components and is trying to improve the process of aligning the mirrors so that Webb is prepared for major observations. The US space agency has provided details on the NIRSpec instrument. 

It said the instrument has a series of microshutters of a quarter of a million miniature movable windows, each measuring between 0.1 and 0.2 millimeters. This Webb microshutter matrix will allow scientists to target specific galaxies in the fields they study, eliminating other celestial bodies or objects that appear in the background, so that the resulting Webb image is clear and concrete on the main object captured. 

The official announcement from the space agency recently said that the Webb team has begun testing for the mechanism and electronics that control and operate the microshutters.

Massimo Stiavelli, Webb Mission Office head, Space Telescope Science Institute said the following:

"The chemical composition of the early universe, just after the big bang, is the product of the nuclear processes that took place in the first few minutes of the universe's existence. These processes are known as 'primordial nucleosynthesis.' One of the predictions of this model is that the chemical composition of the early universe is largely hydrogen and helium. There were only traces of heavier elements, which formed later in stars. These predictions are compatible with observations, and are in fact one of the key pieces of evidence that support the hot big bang model.

"The earliest stars formed out of material with this primordial composition. Finding these stars, commonly dubbed as the 'First Stars' or 'Population III stars,' is an important verification of our cosmological model, and it is within reach of the James Webb Space Telescope. Webb might not be able to detect individual stars from the beginning of the universe, but it can detect some of the first galaxies containing these stars.

"One way to confirm whether we are finding the first stars is to accurately measure metallicities of very distant galaxies. The astronomical term, metallicity, is a measurement of the amount of material heavier than hydrogen and helium - so a low metallicity galaxy would indicate it was made up of these 'First Stars.' One of the most distant galaxies discovered so far, known as MACS1149-JD1, is confirmed to be at redshift 9.1 and emitted the light we see when the universe was only 600 million years old. The light from this distant galaxy has been traveling ever since then and is just reaching us now.

"In the first year of Webb science, I have an observing program to study this galaxy and determine its metallicity. I will do this by attempting to measure the ratio in the strength of two spectroscopic lines emitted by oxygen ions, originally emitted at violet-blue and blue-green visible light (rest frame wavelengths at 4,363 angstroms and 5,007 angstroms). Thanks to cosmological redshift, these lines are now detectable at the infrared wavelengths that Webb can see. The use of a ratio of two lines of the same ion can provide an exquisite measurement of the gas temperature in this galaxy and, through relatively simple theoretical modeling, will provide a robust measurement of its metallicity.

"The challenge is that one of these lines is usually extremely weak. However, this line tends to get stronger at lower metallicity. So if we failed to detect the line and measure metallicity for MACS1149-JD1, that would likely mean that it has already been enriched by the heavier elements, and we need to look further and harder. Whether using my data or with future programs, I fully expect that during its operational lifetime Webb will be able to find objects with metallicity sufficiently low to hold keys for understanding the first generation of stars."



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