This animation reveals the trail gentle will observe because it hits the first James Webb Space Telescope (JWST) mirror, and is mirrored to the secondary, after which in by means of the aft optics meeting the place the tertiary and high quality steering mirrors are. The gentle is then mirrored and cut up and directed to the science devices by pick-off mirrors. JWST is a three-mirror anastigmat telescope. Credit: NASA, ESA, and G. Bacon (STScI)
This week the Webb crew continued to make progress in aligning the telescope to the NIRCam instrument. Between taking the info to know the optical elements, we proceed to take a look at the science devices. The NIRSpec instrument features a microshutter array of a quarter-million miniature movable home windows, every 0.1 by 0.2 millimeters in dimension. The microshutter array permits scientists to focus on particular galaxies in fields they’re learning, whereas closing the home windows on the background or different objects which might contaminate the spectra. We have begun testing the mechanism and electronics that management and actuate the microshutters.
In latest weeks, we shared a way for theoretically modeling the early universe. Today, we’ll focus on an observational program to assist us reply a few of these questions. Massimo Stiavelli, the Webb Mission Office head on the Space Telescope Science Institute, tells us about his deliberate investigations of the primary stars and galaxies:
“The chemical composition of the early universe, simply after the large bang, is the product of the nuclear processes that passed off within the first couple of minutes of the universe’s existence. These processes are generally known as ‘primordial nucleosynthesis.’ One of the predictions of this mannequin is that the chemical composition of the early universe is essentially hydrogen and helium. There have been solely traces of heavier components, which shaped later in stars. These predictions are appropriate with observations, and are in reality one of many key items of proof that help the new huge bang mannequin.
“The earliest stars shaped out of fabric with this primordial composition. Finding these stars, generally dubbed because the ‘First Stars’ or ‘Population III stars,’ is a vital verification of our cosmological mannequin, and it’s inside attain 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.”
– Massimo Stiavelli, Webb Mission Office head, Space Telescope Science Institute
Written by:
- Jonathan Gardner, Webb deputy senior project scientist, NASA’s Goddard Space Flight Center
- Alexandra Lockwood, project scientist for Webb science communications, Space Telescope Science Institute
