SPHEREx is mapping the universe in unprecedented detail

SPHEREx, NASA’s latest space observatory, has officially begun scanning the skies after weeks of careful preparation in orbit. Each day, it captures around 3,600 images to build a vibrant, detailed map of the universe that is unlike anything seen before.

Launched into space on March 11, the observatory was created by scientists from the California Institute of Technology (Caltech), NASA’s Jet Propulsion Laboratory, and other institutions. Over six weeks, the mission team checked and calibrated every part of the observatory to ensure it would perform as planned.

Exploring the origins of the universe

On May 1, SPHEREx entered its full science phase. Over the next two years, it will use its powerful infrared sensors to explore the origins of the universe, trace the history of galaxies, and search for the ingredients of life scattered across our galaxy.

“Thanks to the hard work of teams across NASA, industry, and academia that built this mission, SPHEREx is operating just as we’d expected and will produce maps of the full sky unlike any we’ve had before,” said Shawn Domagal-Goldman, acting director of the Astrophysics Division at NASA Headquarters in Washington.

“This new observatory is adding to the suite of space-based astrophysics survey missions leading up to the launch of NASA’s Nancy Grace Roman Space Telescope. Together with these other missions, SPHEREx will play a key role in answering the big questions about the universe we tackle at NASA every day.”

How SPHEREx sees the universe

SPHEREx, short for Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer, circles Earth roughly 14½ times a day. It follows a polar orbit, passing over the North and South Poles, and captures images in strips that wrap around the planet.

Each day adds another strip. Over six months, the telescope will observe the full sky, and over 25 months, it will do this four times.

To control its movement, the spacecraft doesn’t use thrusters. Instead, it adjusts its orientation using reaction wheels, which are spinning devices inside the observatory.

Unlike some telescopes, SPHEREx doesn’t move its mirrors or detectors to shift its view. Instead, the entire spacecraft tilts slightly to change its pointing direction.

Each image is actually a set of six, with each detector capturing a different part of the infrared spectrum. These are called exposures. SPHEREx takes about 600 exposures every day.

Understanding the beginning of everything

Over two years, the observatory will generate hundreds of thousands of images. These will be woven into four complete maps of the entire sky. Scientists will use them to look for clues about what took place during the earliest moments after the big bang.

One key moment the experts are interested in is called cosmic inflation, which occurred a fraction of a second after the universe began. During this time, the universe expanded faster than the speed of light – to a trillion-trillion times its starting size. This sudden growth left subtle traces in how matter is spread across space.

“We’re going to study what happened on the smallest size scales in the universe’s earliest moments by looking at the modern universe on the largest scales,” said Jim Fanson, the mission’s project manager at NASA’s Jet Propulsion Laboratory in Southern California. “I think there’s a poetic arc to that.”

Echoes of early universe expansion

The positions of galaxies today still carry echoes of early universe expansion. These patterns hold the secrets to what kind of energy triggered inflation. Studying them may reveal something never seen before in nature – the kind of energy that could have powered this vast transformation.

“Some of us have been working toward this goal for 12 years,” said Jamie Bock, the mission’s principal investigator at Caltech and JPL.

“The performance of the instrument is as good as we hoped. That means we’re going to be able to do all the amazing science we planned on and perhaps even get some unexpected discoveries.”

The map has a spectrum of possibilities

While SPHEREx is not the first observatory to chart the entire sky, it is the first to do so in 102 colors of infrared light. That’s far more than previous missions.

Infrared light is invisible to human eyes but carries important information about distant stars, galaxies, and clouds of gas and dust.

The observatory uses a method called spectroscopy to break down light into its component wavelengths, similar to how a prism splits sunlight into a rainbow. Each color tells a different story.

For instance, this method helps determine how far away a galaxy is. That turns a flat map of galaxy locations into a 3D picture of the cosmos. Spectroscopy also lets scientists measure the total light from all galaxies that ever existed and how it has changed over billions of years.

And in our own galaxy, it will help look for key molecules that support life. Water, for example, can be detected in frozen form on dust grains. Scientists believe these icy grains were the source of Earth’s ocean water.

What SPHEREx could reveal next

SPHEREx is expected to make over nine million measurements of interstellar clouds across the Milky Way. These data will help scientists understand how chemistry varies in different space environments. It may even explain how life-friendly molecules found their way to Earth.

With a simple approach and sophisticated tools, this small spacecraft is investigating some of the biggest questions humanity has ever asked. And it’s doing it one image at a time.

Details of SPHEREx and its mission are available in this press release from NASA’s JPL.

Image Credit: NASA/JPL-Caltech

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