SPHEREx is building the most colorful map of the universe ever created

In March of this year, a refrigerator-sized spacecraft unfurled its solar panels 435 miles above Earth and pointed a wide-field space telescope toward the Milky Way’s glittering plane.

Its name is SPHEREx, short for Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer. The scientific appetite of the spacecraft is as sweeping as its title.

Every six months, the observatory will scan the sky in 102 infrared channels – far beyond just a few colors. Unlike most earlier space missions, SPHEREx is already placing those observations into the hands of anyone who wants them.

Rachel Akeson is the head of the mission’s Science Data Center at IPAC, the NASA-funded astrophysics hub on the Caltech campus in Pasadena.

“Because we’re looking at everything – from nearby asteroids to the edge of the observable universe – almost every area of astronomy can be addressed by SPHEREx data,” said Akeson.

Extraordinary power of SPHEREx

The “spectro-photometer” in the spacecraft’s name hints at its extraordinary power. Most survey telescopes capture broadband images – think red, green, and blue filters – then move on.

SPHEREx instead slices incoming infrared light into 102 ultra-narrow bands between 0.75 and 5 microns. Unlike tinted imaging, SPHEREx works like a prism, splitting light into a finely detailed spectrum.

That spectral finesse allows astronomers to identify the telltale fingerprints of specific molecules.

The mission’s core team will use it to map deposits of frozen water, carbon monoxide, methane, and other prebiotic ices. These raw ingredients are scattered through interstellar clouds and can seed newborn planetary systems.

From ice to inflation

On a grander scale, the same data will chronicle the total starlight emitted by galaxies across cosmic time. It will also probe the inflationary physics that rapidly expanded the infant universe just moments after the Big Bang.

The mission follows in the footsteps of NASA’s WISE spacecraft, which delivered four-band infrared maps between 2009 and 2011. SPHEREx’s 102-band upgrade provides roughly eight times the spectral resolution and can detect objects 100 times fainter.

This is a transformative leap for studies of meteoroids in our solar system, stellar nurseries in the Milky Way, and galaxies so distant their light has been traveling for more than 10 billion years.

Telemetry becomes public science

NASA policy mandates that mission data become public, but the speed at which SPHEREx is releasing its archive is unusual. Down-linked telemetry first lands on secure servers at NASA’s Jet Propulsion Laboratory, then heads to IPAC for two months of refinements.

Engineers remove cosmic-ray “snow,” correct subtle detector noise, and stitch overlapping frames to proper celestial coordinates. The final products – calibrated images, spectra, and a catalog of hundreds of millions of objects – arrive at the Infrared Science Archive (IRSA) in weekly batches.

“We want enough information in those files that people can do their own research,” noted Akeson. Detailed processing “cookbooks,” error maps, and metadata tables accompany every release. This allows users to reproduce or refine the data for their own projects.

By mid-mission, the team expects to release the first complete sky atlas mapped in 102 distinct infrared colors.

Three follow-up maps, spaced six months apart, will let scientists track how comets brighten as they near the Sun. They’ll also track brown dwarf motion and quasar flickers as matter spirals into supermassive black holes.

Boosting other space missions

SPHEREx’s value grows even further when scientists combine its data with observations from other spacecraft. Astronomers can mine the catalog to flag unusual targets – say, galaxies magnified by intervening clusters – for the James Webb Space Telescope.

Light curves from NASA’s TESS mission can be cross-checked against SPHEREx spectra to refine the radii and temperatures of newly discovered exoplanets.

Upcoming dark-energy surveys from ESA’s Euclid satellite and NASA’s Nancy Grace Roman Space Telescope will overlay SPHEREx maps to improve distance estimates to millions of galaxies.

Because IRSA already hosts decades of heritage data – from the 2MASS near-infrared survey to Spitzer Space Telescope pointings – researchers can layer SPHEREx results atop mixed-wavelength images with a few clicks.

“SPHEREx is part of the entire legacy of NASA space surveys,” said IRSA science lead Vandana Desai. “People are going to use the data in all kinds of ways that we can’t imagine.”

Weekly SPHEREx data releases

Over its lifetime, the small, relatively inexpensive spacecraft will observe roughly 500 million galaxies, 100 million stars, and thousands of near-Earth asteroids.

It will transform raw bits in a telemetry stream into valuable data. That information will become an open scientific commons for all to explore.

Whether scientists are investigating the cosmic dark ages or hobbyists are hunting for comets in backyard telescopes, the weekly SPHEREx data releases invite everyone to explore.

This infrared rainbow now streaming down from space offers a 102-color guidebook to our cosmic origins. It’s delivered free of charge and ready for the next discovery.

Image Credit: NASA/JPL-Caltech

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