On Tuesday, NASA launched a new space telescope into orbit to explore the origins of the universe. The mission will use sophisticated software, developed at the Arizona Cosmology Lab at the University of Arizona, to analyze data and help astronomers understand what happened in the first trillionth of a second after the Big Bang. 

SPHEREx – which stands for Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer – is a NASA mission that will use a wide-field telescope to gather optical and infrared data on more than 450 million galaxies, as well as more than 100 million stars in the Milky Way, over the course of two years. The U of A is a mission partner, along with the California Institute of Technology, the Jet Propulsion Laboratory, Ball Aerospace, and the Korea Astronomy and Space Science Institute, among others. 

The mission has three goals. Within the Milky Way, it will search for signs of water ice – a major ingredient in the search for life beyond Earth. It will probe the origin and history of galaxies using a fairly new technique called intensity mapping. And it will explore the deep early history of the universe itself.

SPHEREx researchers are interested in understanding what happened during the inflationary epoch, when the universe expanded exponentially in the first fraction of a second after its birth. In the moment of inflation, tiny quantum fluctuations — little irregularities — were blown up through rapid expansion.

These were the seeds in the early universe that eventually gave rise to galaxy formation. The precise infrared capabilities of SPHEREx will allow the mission to measure the distribution of galaxies in order to understand the nuances behind this inflationary process.

Researchers at the Arizona Cosmology Lab are also interested in what can't be seen. Galaxies trace the presence of dark matter, which is thought to have played a role in the formation of galaxies and the evolution of the universe. 

"We're looking for tracers," said Tim Eifler, an associate professor of astronomy at the U of A Steward Observatory. "Galaxies trace the presence of dark matter. Where there are a lot of galaxies, there is likely a lot of dark matter because of gravity."

SPHEREx is unique in that it will measure the whole sky multiple times during its two-year mission. 

"We hope to see the imprints of the very early universe by making the largest 3D map of galaxies that has ever existed," said Elisabeth Krause, an associate professor of astronomy and physics who leads the U of A team for the mission. 

The SPHEREx map will amount to millions upon millions of stars and galaxies. Krause and her team at the Arizona Cosmology Lab will condense the catalog of galaxies into a few summary statistics – an extraordinarily fine-tuned process that involves counting pairs of galaxies as a function of their separation from each other. 

For the mission, former U of A postdoctoral student Yosuke Kobayashi developed a complex mathematical model to pinpoint relevant information about galaxies and discard unnecessary information. To make use of Kobayashi’s mathematical descriptions for SPHEREx, the Arizona Cosmology Lab needed to be able to put the equations into code and to develop software capable of analyzing data and building accurate models of the universe. The lab has turned to machine learning to accelerate the software. 

The state-of-the-art high-performance computing system on the U of A campus makes this kind of innovation possible, according to the research team. 

"Computational speed has always been a bottleneck when predicting what we see in the universe," said Eifler. "We're training a neural network with some of these equations, and when we later run the analysis, it will be much, much faster." 

Once SPHEREx is in orbit, the next chapter of work at the Arizona Cosmology Lab will begin: taking the vast catalog of data and beginning to constrain cosmological models that will help unveil what happened at the dawn of time.