NASA’s SPHEREx space telescope SPHEREx has completed its first full infrared map of the sky in as many as 102 colors, opening a new chapter in cosmic mapping. In just half a year of operation, this relatively compact but extremely sophisticated observatory has managed to “piece together” a panoramic mosaic of the entire sky – from the nearest stars in our galaxy to hundreds of millions of galaxies scattered across nearly 14 billion years of cosmic history. It is the first such 3D “color” map of the universe, intended not only for top scientists but also for the general public, as the data is available to everyone.

SPHEREx – short for Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer – was launched in March 2025 and placed into low Earth orbit. There, it continuously orbits the planet, collecting infrared radiation that is invisible to the human eye but contains key clues about the origin of the universe, the evolution of galaxies, and the “building blocks” for the formation of planets and life. The first all-sky map, completed in December 2025, is just the beginning of a two-year mission during which the telescope will map the entire sky three more times, with increasing precision and sensitivity.

Map of the Universe in 102 Infrared Colors

Unlike classic astronomical images that show the sky in only a few broad infrared or visible bands, SPHEREx observes each part of the sky in 102 narrowly defined infrared wavelengths. Each of these “channels” carries specific information: some are particularly sensitive to the glow of hot hydrogen in cosmic gas, others best reveal cold interstellar dust, and others highlight the light of stars and galaxies. When all these colors are combined, an extremely rich image is obtained – a kind of cosmic rainbow in three dimensions.

In the first mosaic of the entire sky, regions dominated by hot gas, those where dust prevails, and areas where the light of stars and galaxies is visible are clearly distinguished. Hot hydrogen gas emits characteristic “blue” infrared wavelengths, while cold dust stands out in “redder” infrared colors. Combined, this yields a cosmic map that allows scientists to simultaneously track how matter is distributed on the largest scales and how new stars and planets are born in nebulae within our Milky Way.

It is important to emphasize that SPHEREx does not just produce a beautiful image of the sky, but a real three-dimensional map of the universe. Every observed object – from a distant galaxy to a dust cloud in the Milky Way – “signs” itself in the spectrum with a different arrangement of colors. From this signature, it is possible to determine the distance of many galaxies, and thus their position in the 3D distribution of matter throughout the entire visible universe.

How the SPHEREx Telescope Scans the Entire Sky

SPHEREx orbits the Earth about 14 and a half times a day, in an orbit that takes it from the North to the South Pole. During each orbit, it captures one narrow strip of the sky, much like a band stretching around the entire celestial sphere. Every day, about 3,600 individual images are created, which are then digitally merged into a larger mosaic. As the Earth travels around the Sun, the telescope's view slowly shifts, so after about six months, SPHEREx “sees” every point in the sky.

The first systematic mapping of the sky began in May 2025. In the following six months, until the end of December, a complete set of data was collected and used to create the first comprehensive infrared map of the sky in 102 colors. The mission is designed to perform four such scans of the entire sky over a two-year period. By merging multiple maps, overall sensitivity increases – faint objects that were only vaguely indicated in the first pass become clearer and more measurable after several “passes.”

To move its view across the sky stably and precisely, SPHEREx does not use small rocket engines but a system of so-called reaction wheels – internal flywheels that change the spacecraft's orientation by rotation. This approach reduces vibration and allows the telescope to remain extremely stable during imaging, which is crucial for obtaining sharp infrared images that are later merged into a unique mosaic. In total, more than 11,000 orbits and hundreds of thousands of individual images will be completed during the nominal mission.

Spectroscopy: Turning Colors into Coordinates and Chemical Signatures

The key “superpower” of the SPHEREx telescope is spectroscopy, a technique by which light is decomposed into its constituent wavelengths. At the simplest level, this is analogous to a prism breaking white light into a rainbow, but here it is a much finer and more precisely calibrated decomposition of infrared radiation. Every molecule and every chemical element leaves a recognizable trace in the spectrum – a set of specific lines and colors.

To achieve this, SPHEREx uses six detectors, and in front of each is a specially designed filter with a gradient of 17 different colors. When the telescope captures one field, six images are obtained simultaneously, each in a series of different infrared wavelengths. Together they make up 102 separate “channels”, from the shortest to the longest wavelengths covered by the instrument. Each complete map of the sky is therefore actually a set of 102 “sub-maps,” where each color highlights different structures in the universe.

Spectroscopy also allows for estimating the distances of many galaxies. As the universe expands, light from distant galaxies “shifts” toward redder wavelengths – a phenomenon known as redshift. By how much the spectrum is shifted, scientists can calculate how far away a galaxy is and how old the light reaching us is. SPHEREx will measure distances for hundreds of millions of galaxies in this way, turning a two-dimensional projection of the sky into a three-dimensional map of cosmic structure.

A particular strength of SPHEREx is the combination of a wide field of view and a large number of colors. Classic space telescopes like Hubble or James Webb (JWST) can study smaller areas of the sky with very high spatial and spectroscopic resolution, but over a limited area. SPHEREx, by contrast, is designed as a “cosmic cartographer” – covering the entire sky, but with moderate spatial resolution and an extremely rich spectrum. Together, such instruments form a powerful system: SPHEREx finds interesting targets and statistical patterns, while Webb, Euclid, Roman, and other telescopes dive into the details.

Inflation: Traces of the Earliest Moments After the Big Bang

One of the main scientific goals of the mission is to research the mysterious period of cosmic inflation. According to today's models, the universe underwent an incredibly rapid expansion in the first fraction of a second after the Big Bang: in the first trillionth of a trillionth of a trillionth of a second, space expanded by a factor of roughly a “trillion trillion.” No other known process in physics involves such an amount of energy and such extreme scales.

Although inflation occurred unimaginably quickly and long ago, its traces can be seen in today's distribution of galaxies on the largest scales in the universe. Small quantum fluctuations in the very early universe were stretched to cosmic proportions by inflation; over time, they became the seeds around which matter began to gather and galaxies, galaxy clusters, and massive cosmic “filaments” were formed. The way galaxies are distributed in space today therefore carries information about what exactly inflation was like.

Thanks to millions of measured galaxies and their distances, SPHEREx will enable very precise statistical measurements of these distributions. By comparing observations with different theoretical models of inflation, scientists will be able to exclude some scenarios and narrow down the possibilities. The goal is not just to confirm that inflation happened, but to understand its physical nature: what kind of field caused the expansion, how it behaved, and what that tells us about the fundamental laws of physics.

Water and Organic Compounds in the Milky Way

The second major scientific task of SPHEREx concerns the building blocks of life. In cold molecular clouds within our galaxy, far from bright stars, there are huge amounts of ice and organic compounds deposited on tiny dust grains. When new stars and planetary systems form from such clouds, this ice is incorporated into protoplanetary disks and later into comets and planets.

It is believed that a significant portion of the water in Earth's oceans originated in precisely this way – as ice in an interstellar cloud from which the Solar System was born. By studying the infrared “signatures” of water, hydrocarbons, and other molecules in spectra, SPHEREx can map where these ingredients are located in the Milky Way and in what quantities. Molecules such as polycyclic aromatic hydrocarbons (PAHs) are particularly interesting, as they behave like “smoke” or soot on cosmic scales – glowing in some wavelengths and completely disappearing in others.

During the mission, SPHEREx will perform millions of individual measurements of such clouds across the entire galaxy. The result will be a map showing where in the Milky Way cold clouds rich in water and organic compounds dominate, and where regions of strong radiation that break these molecules prevail. Such a map will help astrophysicists better understand the conditions under which planetary systems like ours are born and how common scenarios are in which planets receive generous supplies of water early in their formation.

In addition to our galaxy, SPHEREx will also track the total amount of light emitted throughout the history of the universe by all galaxies together – the so-called cosmic infrared background light. This is another way to reconstruct the history of star formation, dust creation, and the spread of complex chemistry over billions of years.

SPHEREx in the Company of Other Space Telescopes

SPHEREx is not the only telescope to have mapped the entire sky in the infrared range – it was preceded, for example, by NASA's WISE (Wide-field Infrared Survey Explorer), which also produced a full-sky map in the 2010s. However, WISE operated in only four broad infrared bands, while SPHEREx covers more than a hundred narrow wavelengths. The result is much finer “color” information, ideal for spectroscopic analysis and precise determination of distances and chemical composition.

On the other side of the spectrum is the James Webb Space Telescope, specialized for detailed, deep observations of small areas of the sky. Webb can study the atmospheres of exoplanets or the structure of individual galaxies with incredible precision, but it cannot quickly collect data for the entire sky. SPHEREx fills precisely that niche: it creates a context in which individual deep observations can be better understood, because it shows how a specific object fits into the bigger picture.

Alongside Webb, SPHEREx will collaborate with missions such as the European telescope Euclid, specialized in studying dark matter and dark energy, and NASA's future Nancy Grace Roman telescope. SPHEREx can, for example, help in selecting targets for more detailed imaging or provide additional data on galaxies already in the catalogs of those missions. This creates a network of complementary observatories where each instrument performs what it is best suited for.

A Small Mission with a Large International Team

Although in NASA's hierarchy SPHEREx is classified among the so-called medium-sized (MIDEX) astrophysical missions, the amount of science it will produce is proportional to much larger and more expensive projects. The telescope and spacecraft were built by BAE Systems, while the installation of the instrument and system was coordinated by the California Institute of Technology (Caltech), an institution that also manages NASA's Jet Propulsion Laboratory (JPL).

The scientific team brings together researchers from ten institutions in the United States and partner groups in South Korea and Taiwan. Such international cooperation has become standard in modern astrophysics: building a space telescope requires industrial experience, the development of advanced detectors, and complex software tools, while data analysis involves entire generations of PhD students and postdocs who will base their papers and careers on SPHEREx.

For the leadership of NASA's Astrophysics Division, SPHEREx is an example of how bold ideas can be realized in a medium-sized mission. With a carefully designed instrument and clearly defined scientific goals, it is possible to obtain data relevant to fundamental questions of cosmology and astrophysics – from inflation to the distribution of water in the galaxy – for a relatively limited budget.

Open Science: Data Available to Everyone

One of the most important features of the mission is its commitment to open science. Since the beginning of scientific operations, SPHEREx has regularly sent data to NASA's infrared observation archive, managed by the IPAC center at Caltech. After the scientific team removes instrumental artifacts, calibrates images, and checks quality, the data is released as public sets. The first complete infrared map of the sky is now available to professional astronomers as well as advanced amateurs or curious users.

During the two-year nominal mission, SPHEREx is planned to rescan the entire sky four times. After about one year of operation, NASA announced the release of a complete map in all 102 infrared colors as a reference catalog. Each subsequent pass will further improve sensitivity and enable the detection of increasingly faint sources. As the archive fills, the potential for unexpected discoveries will grow – from rare types of galaxies to unusual dust clouds and new clues about the formation of planetary systems.

For astronomers planning observations with other telescopes, SPHEREx offers a valuable “preview” of the sky. Researchers can search the archive for areas of interest, check for unusual spectroscopic signatures or high concentrations of dust and gas, and adjust their detailed observations accordingly. At the same time, the reverse scenario is equally possible: objects accidentally discovered by other missions can be analyzed in a broader context in SPHEREx maps and linked to the environment surrounding them.

As the mission progresses, the amount of data will grow exponentially, and SPHEREx's first sky map will serve as a reference point for the next decade of research. It serves as a reminder that even a relatively compact telescope, placed in a low orbit around the Earth, can open a window to the earliest moments of the universe and simultaneously track the path of water and organic molecules that might one day, somewhere, end up in the oceans of another world.