It’s a telescope designed to help scientists answer fundamental questions about everything from finding water-bearing sites in the Milky Way to what happened in the first seconds after the Big Bang. Launched this March, NASA’s SPHEREx space observatory has completed its first infrared map of the entire universe in 102 “colors.” However, these cannot be seen with the naked eye (hence the word color in quotes) as they are 102 wavelengths of infrared radiation. Observing the entire sky in this way will allow scientists to find answers to questions, including how the dramatic event that occurred in the first billionth of a trillionth of a trillionth of a second after the Big Bang affected the three-dimensional distribution of the hundreds of millions of galaxies in our universe. In addition, scientists will use the data to study how galaxies have changed over their nearly 14 billion-year history. They can also learn about the spatial distribution of key ingredients for life in our galaxy.
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„It’s incredible how much information SPHEREx was able to collect in just six months – information that will be extremely valuable when used together with data from other missions to better understand the universe,” says Shawn Domagal-Goldman, director of the Astrophysics Division at NASA Headquarters in Washington, adding: “Basically we have 102 new maps of the whole sky. Each one is at a different wavelength and contains unique information about the objects it sees. I think every astronomer will find something of value there, as NASA’s missions allow the world to answer fundamental questions about how the universe began and how it changed to eventually form our home.“
SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer) will orbit the Earth roughly 14.5 times a day from north to south and back again across the poles. Each day, it takes roughly 3,600 images along one circular swath of the sky. As the days pass and the planet moves around the Sun, the field of view of the SPHEREx shifts as well. After six months, the observatory was already looking into space in every direction – capturing the entire sky in a 360° range. The mission, managed by California’s Jet Propulsion Laboratory, began mapping in May, and the first full-sky mosaic was completed in December. It is scheduled to produce three more scans of the entire sky during its two-year primary mission. Combining these maps will increase the sensitivity of the measurement. The entire dataset is freely available to scientists and the public. “SPHEREx is a medium-sized astrophysics mission, but one that delivers big science,” stated Dave Gallagher, director of JPL, adding: “It is a phenomenal example of how we can turn bold ideas into reality, unlocking enormous potential for discovery.“
Each of the 102 “colors” recorded by SPHERex represents one wavelength of infrared radiation. Each wavelet provides unique information about galaxies, stars, planet-forming regions, and other cosmic phenomena. For example, the dense clouds of dust in our galaxy, where stars and planets form, shine brightly at some wavelengths, but hardly shine at all (and are therefore invisible) at others. The process of separating radiation from a source into the wavelengths that make it up is called spectroscopy. Although there have been several previous missions that have also mapped the entire sky (including NASA’s Wide-field Infrared Survey Explorer), none of them have done so in nearly as many “colors” as SPHEREX. In contrast, the James Webb Space Telescope can perform spectroscopy at significantly more wavelengths than SPHEREx, but on a field of view that is several thousand times smaller. It is the combination of the number of “colors” and such a wide field of view that makes SPHEREx so powerful.
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„SPHERex’s superpower is that it captures the entire sky in 102 colors every 6 months. That’s an amazing amount of information collected in a short amount of time,” says Beth Fabinsky, SPHEREx mission project manager at JPL, adding: “I think this makes us the “mantis shrimp” of binoculars because we have an amazing multi-color visual detection system and can also see a very wide swath of our surroundings.” To achieve this exceptionality, SPHEREx uses six detectors, each paired with a specially designed filter containing a transition between 17 “colors”. This means that each image taken by these six detectors contains 102 “colors” (6×17 = 102). This also means that each all-sky map that SPHEREx produces is actually made up of 102 maps – each at a different wavelength.
The observatory will use these “colors” to measure the distances of hundreds of millions of galaxies. Although the positions of most of these galaxies have already been mapped by other observations in two dimensions, SPHEREX’s map will be in 3D, allowing scientists to measure small variations in the way galaxies cluster and how they are dispersed in space. These measurements will offer better insight into the events that occurred in the first billionth of a trillionth of a trillionth of a second after the Big Bang. In this phase, called inflation, the universe expanded a trillion trillion times. Nothing like this has happened in space since, and scientists want to better understand this process. The SPHEREx mission approach is one way to advance these efforts.
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