"This is the first mission to view the entire sky in so many colors," said Jamie Bock, principal investigator of SPHEREx, which operates jointly at NASA's Jet Propulsion Laboratory (JPL) and Caltech.
NASA's SPHEREx instrument, scheduled for launch by April 2025, will survey hundreds of millions of galaxies in 102 infrared colors to examine the expansion of the universe, light emissions from galaxies and molecules essential to life, thereby improving our cosmic understanding.
NASA's SPHEREx mission
Although it won't be the first telescope to study hundreds of millions of stars and galaxies, SPHEREx will be the first mission to do so in 102 infrared colors. These colors are not visible to the human eye, but scientists will use SPHEREx's infrared data to investigate diverse questions, from the physics that shaped the universe in its first moments to the sources of water on planets such as Earth.
"This is the first mission to view the entire sky in so many colors," said Jamie Bock, principal investigator of SPHEREx, which operates jointly at NASA's Jet Propulsion Laboratory (JPL) and Caltech in Southern California. Looking at the sky in a new way, one can expect discoveries."
Integration and testing of the SPHEREx observatory
SPHEREx, an acronym for Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer, will collect infrared light at wavelengths slightly longer than those visible to the human eye. The telescope will use spectroscopy to break down the light from stars and galaxies into millions of separate colors, similar to how a prism breaks up sunlight into a rainbow. This detailed color analysis can reveal the object's composition, its distance from Earth, and other important features.
The study of cosmic origins
What the human eye perceives as colors are separate wavelengths of light. The only difference between colors is the distance between the peaks of the wave. If a star or galaxy moves, their light waves are stretched or compressed, which changes the colors they emit. Astronomers can measure how much light is stretched or compressed and use that to infer the distance to the object.
SPHEREx applied this principle to map the location of hundreds of millions of galaxies in 3D. In this way, scientists will be able to study the physics of inflation, the event that caused the universe to expand trillion-trillion times in less than a second after the Big Bang. This rapid expansion amplified small differences in the material distribution. Since these differences remain embedded in the distribution of galaxies today, measuring the distribution can tell scientists more about how inflation works.
The origins of galaxies
SPHEREx will also measure the total luminosity produced by all nearby and distant galaxies – that is, the total amount of light that the galaxies have emitted during cosmic history. Scientists have tried to estimate the total light output by observing individual galaxies and extrapolating to the billions of galaxies in the universe. But these estimates may miss faint or hidden light sources, such as galaxies too small or too far away for telescopes to easily detect.
Using spectroscopy, SPHEREx will be able to show astronomers how the total light output has changed over time. For example, it may reveal that the first generations of galaxies produced more light than previously thought, either because they were more numerous or larger and brighter than current estimates. Since light takes time to travel through space, we see distant objects as they were in the past. And during the light's journey, the expansion of the universe stretches it, changing its wavelength and color. Scientists can therefore use the SPHEREx data to determine how far the light traveled and at what point in time in cosmic history it was emitted.
the water sources
SPHEREx will measure the abundance of frozen water, carbon dioxide and other molecules essential to life as we know it along more than 9 million unique directions in the Milky Way galaxy. This information will help scientists better understand how available these important molecules are for planet formation. Studies indicate that most of the water in our galaxy is in the form of ice rather than gas, frozen on the surface of small dust grains. In dense star-forming clouds, these frozen dust grains may become part of new planets, with the potential to create oceans like those on Earth.
The mission's colorful view will allow scientists to identify these substances, because chemical elements and molecules leave a unique signature in the colors they absorb and emit.
The big picture
Many space telescopes, such as the Hubble and NASA's James Webb Space Telescope, can provide high-resolution and in-depth spectroscopy of single objects or small regions of space. Other telescopes, such as NASA's (now defunct) WISE Space Telescope, were designed to image Pictures of the whole sky. SPHEREx combines these capabilities to apply all-sky spectroscopy.
By combining observations from telescopes targeting specific regions of the sky with SPHEREx's overall view, scientists will gain a more complete—and more colorful—perspective of the universe.
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