NASA expects to soon launch a mission to create the most colorful 3D map of the entire sky yet. Known as SPHEREx, it will analyze every pixel to see what’s there, what it’s made of, and how far away it is in an attempt to answer some of the most profound questions ever asked.
The craft is set to launch on Friday 28 February, after which it will scan the whole sky four times over the course of the next two years. By the end of the mission, every point above will have been captured in an infrared rainbow of 102 colors – far more than any other all-sky map.
“We will look at everything in the sky and get a spectrum for every pixel no matter what is there – comets in our Solar System, planets, stars, galaxies,” says Olivier Doré, an astrophysicist at NASA’s Jet Propulsion Laboratory and project scientist for SPHEREx.
“We expect our data set to expand our broad knowledge of the cosmos: Whatever your favorite object in the sky is, we will measure its spectrum.”
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A classic awkward acronym, SPHEREx stands for Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer, which sums up a mission that consists of three main objectives.
First is to study what the Universe looked like in the fractions of a second after the Big Bang. Second, it will attempt to tally up all the light that has ever been emitted from all galaxies. And third, it will try to take stock of water and other vital ingredients for life in the Milky Way galaxy.
These lofty goals will (hopefully) be made possible by collecting data on the spectrum of light that reaches the SPHEREx observatory from throughout the cosmos. By analyzing how stretched or compressed the wavelengths appear, researchers can determine how far away the source is and whether it’s moving towards or away from us.
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The end result will be a gigantic, three-dimensional chart consisting of the relative locations of some 450 million galaxies. This map could then be used to test models of cosmic inflation – the brief period just after the Big Bang, when the Universe inflated to septillions of times its size within fractions of a quectosecond.
The distribution of galaxies in the cosmic web was likely set during this inflationary period, so SPHEREx will measure the density of galaxies throughout the Universe. If it’s roughly the same everywhere, we could have a simple inflation model, perhaps involving a hypothetical particle called the inflaton. If it’s skewed, however, multiple unknown fields and particles could be at work.
Scientists could also use SPHEREx’s 3D map to pull off a feat that sounds impossible: calculate all light that has ever been emitted by galaxies throughout the history of the Universe. The data can indicate how far light has traveled, where it came from, when it was emitted, and how the total light output has changed across cosmic history.
Closer to home, SPHEREx data could help illuminate the likelihood of life elsewhere in our galaxy, by searching for signatures of water ice and other compounds locked away in star-forming molecular clouds.
Each element and compound has its own spectral fingerprint based on how its atoms absorb and emit different wavelengths of light. Scientists can use this to figure out what’s in a molecular cloud by analyzing background light filtering through its particles.
SPHEREx will make more than 9 million observations of these clouds, gathering data in 3D along its line of sight each time to detect water ice, carbon dioxide, carbon monoxide, and other materials that are vital for life. If they’re present in large amounts in these clouds, they’re more likely to infiltrate planets born there, giving any potential life a better foothold.
Whatever it finds, SPHEREx will prove to be a treasure trove of data for scientists well into the future. It could be especially useful when paired with other observatories, like JWST, which has a far narrower but deeper field of vision.
“If SPHEREx discovers a particularly intriguing location, Webb can study that target with higher spectral resolving power and in wavelengths that SPHEREx cannot detect,” says Gary Melnick, an astronomer on the SPHEREx science team.
“These two telescopes could form a highly effective partnership.”
