"We are the first mission to look at the whole sky in so many colors," said SPHEREx Principal Investigator Jamie Bock from NASA's Jet Propulsion Laboratory and Caltech. "Whenever astronomers look at the sky in a new way, we can expect discoveries."

SPHEREx, which stands for Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer, will capture infrared light-beyond the visible range of human sight. Using spectroscopy, it will separate light from stars and galaxies into hundreds of individual colors, revealing information about their properties, including their composition and distance from Earth.

The mission will address three main questions about the cosmos:

Exploring Cosmic Origins

The colors we perceive are actually different wavelengths of light. When a star or galaxy moves, the light waves stretch or compress, changing the perceived color-a phenomenon similar to the changing pitch of a passing siren. By analyzing the change in color, SPHEREx will map the positions of millions of galaxies in 3D, helping researchers explore cosmic inflation, the rapid expansion that occurred immediately after the big bang. The current arrangement of galaxies preserves information about this early event, offering insights into the forces that drove it.

Studying Galactic Light History

SPHEREx will also measure the cumulative glow of all galaxies across the universe, revealing how the total light emitted by galaxies has evolved over cosmic history. This total, known as the "cosmic light budget," can provide hints about the first generations of stars and galaxies, including the possibility that they were more numerous or brighter than previously estimated. Since observing distant light also means looking back in time, SPHEREx will allow scientists to understand how these early celestial bodies contributed to the universe's light as they existed billions of years ago.

Tracing the Origins of Water

In the Milky Way, SPHEREx will examine frozen water, carbon dioxide, and other essential molecules for life. Measuring these compounds in millions of different locations will help researchers understand how they might be incorporated into planets. Most water in the Milky Way is believed to be in ice form, clinging to dust grains. These grains can eventually become part of new planets, potentially bringing with them the ingredients for oceans like those found on Earth. By breaking down light into its components, SPHEREx will identify the unique signatures of these key molecules.

The Broader View

Previous space telescopes like NASA's Hubble and James Webb have focused on high-resolution studies of individual objects or small sky regions, while others like the Wide-field Infrared Survey Explorer (WISE) provided wide-angle imaging of the whole sky. SPHEREx will bridge these capabilities by applying spectroscopy across the entire sky, offering a comprehensive and colorful view of the cosmos.

Combining SPHEREx's observations with those from other space telescopes will yield a richer, broader understanding of the universe.