NASA’s Webb to uncover riches of the early universe
For decades, telescopes have helped us capture light from galaxies that formed as early as 400 million years after the Big Bang — incredibly early in the context of the universe’s 13.8 billion-year history. But what were such galaxies that existed even earlier, when the universe was semi-transparent at the beginning of a period known as the Age of Reionization? NASA’s next flagship observatory, the James Webb Space Telescope, is poised to add new riches to our wealth of knowledge, not only by capturing images of galaxies that existed in the first few hundred million years after the Big Bang, but also known as spectra by us detailed data. With Webb’s observations, researchers can tell us for the first time about the composition and composition of individual galaxies in the early Universe.
The Next Generation Deep Extragalactic Exploratory Public (NGDEEP) Survey, co-led by Steven L. Finkelstein, an associate professor at the University of Texas at Austin, will focus on the same two regions that make up the Hubble Ultra Deep Field sites in the constellation Fornax where Hubble spent more than 11 days shooting deep exposures. To produce its observations, the Hubble Space Telescope simultaneously focused on nearby regions of the sky with two instruments — slightly offset from each other — known as a primary and a parallel field. “We have the same advantage with Webb,” Finkelstein explained. “We are using two scientific instruments at the same time and they will observe continuously.” They will aim Webb’s Near-Infrared Imager and Slitless Spectrograph (NIRISS) at the primary Hubble Ultra Deep Field, and Webb’s Near-Infrared Camera (NIRCam) at the parallel field, giving them twice the value for money in telescope time.
For the imaging with NIRCam, they will observe for more than 125 hours. With each minute that passes, they are extracting more and more information from deeper and deeper in the universe. What are they looking for? Some of the earliest galaxies to form. “We have really good evidence from Hubble that there are galaxies at some point 400 million years after the Big Bang,” Finkelstein said. “The ones we see with Hubble are quite large and very bright. It’s very likely that there are smaller, fainter galaxies that formed even earlier and waiting to be found.”
This program will only use about a third of the time Hubble has spent on similar studies thus far. Why? This is partly because Webb’s instruments are designed to capture infrared light. As light travels toward us through space, it extends into longer, redder wavelengths due to the universe’s expansion. “Webb will help us push all the boundaries,” said Jennifer Lotz, co-investigator of the proposal and director of the Gemini Observatory, part of the National Science Foundation’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory). “And we’re going to release the data immediately to benefit all researchers.”
These researchers will also focus on identifying the metal content in each galaxy, especially in smaller and fainter galaxies that have not yet been thoroughly explored, especially with the spectra provided by Webb’s NIRISS instrument. “One of the fundamental ways we track evolution in cosmic time is through the amount of metals that are in a galaxy,” explains Danielle Berg, an assistant professor at the University of Texas at Austin and a co-investigator of the proposal. When the universe began, there was only hydrogen and helium. New elements were formed by successive generations of stars. By cataloging the contents of each galaxy, the researchers can plot exactly when different elements existed and update models that project how galaxies evolved in the early universe.
Peel off new layers
Another program, led by Michael Maseda, an assistant professor at the University of Wisconsin-Madison, will examine the primary Hubble Ultra Deep Field using the microshutter array within Webb’s Near-Infrared Spectrograph (NIRSpec). This instrument returns spectra for specific objects, depending on which miniature hatches researchers open. “These galaxies existed during the first billion years in the history of the universe, about which we have very little information until now,” explains Maseda. “Webb will provide the first large sample that gives us a chance to understand them in detail.”
We know that these galaxies exist thanks to the extensive observations this team has made – together with an international research team – with the Multi Unit Spectroscopic Explorer (MUSE) instrument of the Very Large Telescope on the ground. While MUSE is the “explorer” identifying smaller, fainter galaxies in this deep field, Webb will be the first telescope to fully characterize their chemical makeup.
These extremely distant galaxies have important implications for our understanding of how galaxies formed in the early Universe. “Webb will open up a new space for discovery,” explains Anna Feltre, a researcher at the National Institute of Astrophysics in Italy and a co-investigator. “The data will help us learn exactly what happens when a galaxy forms, including what metals they contain, how fast they grow, and whether they already have black holes.”
This survey will be conducted as part of Webb’s General Observer (GO) programs, which are competitively selected using a double-anonymous rating, the same system used to allocate time to the Hubble Space Telescope.
The first full-color, scientific images from the Webb telescope are coming in July
Quote: NASA’s Webb to Discover the Riches of the Early Universe (June 2022, June 22) retrieved June 22, 2022 from https://phys.org/news/2022-06-nasa-webb-uncover-riches-early.html
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