NASA
Data from the Webb Space Telescope has only been in the hands of astronomers for the past few weeks, but they’ve been waiting for it for years and it looks like analyzes are underway. The result was more like a race in time, as new discoveries unearthed objects that formed closer and closer to the Big Bang that produced our universe. Last week, one such search revealed a galaxy that existed less than 400 million years after the Big Bang. A new survey this week identified a galaxy that appeared just 233 million years after the birth of the universe.
This discovery is a happy byproduct of work designed to answer a larger question: How many galaxies should we expect to see at different times after the Big Bang?
in time
As we reported last week, the early universe was opaque to light at all wavelengths carrying more energy than is needed to ionize hydrogen. This energy is in the ultraviolet part of the spectrum, but the redshift caused by the 13 billion years of expansion of the universe has moved this cutoff point to the infrared part of the spectrum. To find galaxies of this age, we need to look for objects that are not visible at shorter infrared wavelengths (meaning the light was once above the hydrogen threshold), but appear at lower energy wavelengths.
The deeper the boundary between the invisible and the visible in infrared, the stronger the redshift and the farther away the object is. The farther away an object is, the closer the time to the Big Bang.
Studies of these galaxies can tell us something about their individual properties. But identifying a large group of early galaxies can help us determine how quickly they formed and identify any changes in galactic dynamics that occurred at a specific time in the universe’s past. This change over time in the frequency of visible objects is called the ‘luminosity function’, and work has been done to characterize the luminosity function of early galaxies. But the infrared wavelengths of the first galaxies are absorbed by the Earth’s atmosphere, and therefore must be imaged from space. This was one of the design goals of the Webb telescope.
The new work focused on examining the luminosity function of galaxies that formed shortly (astronomically speaking) after the Big Bang. But by creating a catalog of early galaxies, researchers have discovered what appears to be the oldest galaxy ever photographed.
Job Definition
The researchers used two data sources to reconstruct the appearances of galaxies at different times. One was produced by analyzing work done with the terrestrial infrared telescope (the Vesta telescope) and the Spitzer Space Telescope, both of which imaged relatively older galaxies when they produced the light that now reaches Earth, some 600 million years or more after the Big Bang. Other embedded data generated by Webb, including the datasets analyzed in the article we report on and the region depicted in our first public image publication. In all cases, the researchers looked for the same thing: objects present at the longer infrared wavelengths but absent at the shorter wavelengths.
In total, the team identified 55 distant galaxies, 44 of which had not been observed before. Thirty-nine of them come from Web data, and this number includes the two ancient galaxies identified last week. The numbers are not particularly accurate for higher redshifts, as they are based on only one or two galaxies. But in general, the trend is for a gradual decrease in visible objects up to a few hundred million years since the Big Bang, without sudden changes or breaks.
But surprisingly, there is data for a galaxy at a very large redshift (z = 16.7, for those who understand this stuff). This places it less than 250 million years after the Big Bang. This distance depends in part on the fact that the first wavelength filter in which the object appears appears to be very faint there, indicating that it is faint at the wavelengths the filter leaves behind. This indicates that the light cutoff from the hydrogen is located near the edge of the filter band.
Like the distant galaxies described last week, it also appears to have the equivalent of a billion suns in the form of stars. Researchers estimate that it could have started forming stars as early as 120 million years after the Big Bang, and certainly did so about 220 million years ago.
The researchers are quite confident that this new galaxy represents a real discovery: “After extensive research, we are currently unable to find a reasonable explanation for this object, other than a new redshift galaxy.” And by adding a second, independent confirmation of previous galactic discoveries, it greatly increases our confidence in those discoveries. All of this suggests that the new telescope lives up to its promise, at least when it comes to early galaxies.
The big question now is what will happen when referring to regions with high lenses, which may be able to zoom in on objects to a point where we can image the structures within these early galaxies. We’ve probably already done this, but we’ll have to wait for the descriptions to appear in the arXiv file.
arXiv file. Abstract number: 2207.12356 (about arXiv).