Searching the entire sky for the secrets to our universe

As soon as the end of February, NASA and the Jet Propulsion Laboratory will launch a new telescope into orbit around the Earth called SPHEREx. Its goal is to examine nothing less than the essential ingredients of life in our galaxy and the origin of the universe itself.

SPHEREx will join the ranks of other space telescopes, filling in a crucial gap by detecting infrared light with wavelengths too long to see with the naked eye. It’s an important addition because no single instrument can fully perceive the universe and its contents.

The new telescope’s infrared detectors have to be kept super cold, so the instrument is housed inside three concentric cones atop a set of mirrors that protect it from the sun’s energy and the spacecraft’s own heat. The whole thing looks like a giant funnel.

“It weighs a little less than a grand piano and uses about 270, 300 watts of power — less than a refrigerator,” said Beth Fabinsky, SPHEREx’s deputy project manager, at a press conference in late January.

Other telescopes like Hubble and the James Webb Space Telescope can see celestial objects in exquisite detail but have a fairly limited field of view. SPHEREx, by contrast, “has a very large field of view and we see the entire sky twice each year,” said Fabinsky.

Such a vast view of the sky is intended to allow astronomers to answer some of the biggest questions of all — like how we got here.

“I expect the unexpected to come out of the data for this mission,” said James Fanson, the project manager of SPHEREx.

Everything in no time at all

A mere billionth of a trillionth of a trillionth of a second after the Big Bang, our universe expanded dramatically — a trillion-trillion fold.

“And that expansion expanded tiny fluctuations smaller than an atom to enormous cosmological scales that we see today traced out by galaxies,” said Jamie Bock, SPHEREx’s principal investor based at CalTech, who also spoke at the press conference.

Astronomers agree on this general picture of what happened in the earliest moments of the universe, but they still don’t know what propelled the expansion or why it happened in the first place. The goal of the new telescope is to help answer those questions by mapping the position of several hundred million galaxies across the entire sky.

“We won’t see the Big Bang itself,” said Bock, “but we’ll see the aftermath from it and learn about the beginning of the universe that way. We can use [infrared] to determine the distance to galaxies to build up that three-dimensional map.”

A few hundred million years after the Big Bang came a period known as the cosmic dawn when the first stars and galaxies were born. Star formation peaked some five billion years later and it’s been on a slow decline ever since, according to Bock. But astronomers worry they may not be accounting for all the light inside galaxies that may be too tiny, too diffuse, or too far away for other telescopes to have detected.

“SPHEREx is going to address this subject in a novel way,” said Bock. “It’s going to look at the total glow produced by all galaxies. And by looking this way, we can see if we’ve missed any sources of light.” This could allow Bock and others to find galaxies that, until now, have been hidden.

Finding the fingerprints of life

Infrared can also be used to detect the unique fingerprints of particular molecules in the universe, including the basic components of life — water and organic materials frozen in the ices of interstellar dust clouds where stars are born.

“This is a topic of some interest for us on Earth,” said Bock, “because the water we see here on Earth’s oceans — astronomers believe that initially came from these interstellar reservoirs of ices.”

All the data the telescope collects will be freely accessible to scientists, including those not involved in the development of SPHEREx like Stephanie Jarmak, a planetary scientist at the Harvard and Smithsonian Center for Astrophysics.

“The way it’s designed,” she says, “it’s going to be really useful to a whole host of different science questions and opportunities.”

For Jarmak, that includes examining objects within our own solar system, like asteroids. She says that SPHEREx’s infrared detectors will help her identify particular asteroids of interest, which she can then look at in more detail using other telescopes like James Webb.

“It’s always exciting to have a new suite of observations available,” says Jarmak.

Fabinsky is also excited. “If Hamlet is right and there are more things in heaven and Earth than are dreamt of in our philosophies, SPHEREx may capture that in its all-sky spectral survey,” she said at the close of her press conference remarks.