Astronomy Cast · Fraser Cain and Dr. Pamela Gay

Astronomy Cast Ep. 756: SphereX

May 19, 2025·28 min·2 clips

SphereX uses a single rainbow filter to capture 102 wavelengths without swapping filters.

First, a star will not cooperate. Pamela is annoyed that T. coronaborealis still has not produced the recurrent nova they were waiting for. Fair enough. Astronomy can make predictions, but the sky does not care about anyone's schedule. Then Spherax takes over. The problem is simple to ask and hard to solve: how can a mission study early cosmic history when Earth is stuck with one viewpoint? The cosmic microwave background gives one shell of ancient light, from the moment electrons and protons joined up and photons could finally travel freely. From here, we do not get a second shell to compare. So the episode turns to galaxies as the workaround. Their large-scale arrangement may help round out that one background view. This is the wild part. The hot and cold pattern in the cosmic microwave background grew into the large-scale structure we see now. Run that structure backward, and the modern galaxy pattern may still carry clues about inflation very early in the universe. Fraser catches a useful wording snag when Pamela says epoch of inflation. He checks whether she means reionization, and the correction becomes part of the lesson. She means inflation after all, shortly after the Big Bang. The signal they want is not just another galaxy measurement. It is a footprint in the statistical spread of cosmic structures. A Gaussian distribution would fit one epoch of inflation. A non-Gaussian one could suggest multiple waves. Spherax sits beside Roman and JWST in that bigger effort to build a fuller three-dimensional model of cosmic evolution.

As heard by us

A cosmology discussion that turns galaxy maps into clues about the early universe.

Astronomy Cast uses this episode to treat the universe's large scale structure as a clue to what happened very early on. Fraser and Pamela keep returning to the basics: you cannot jump to another era, so you sample different shells of space, count galaxies, and work backward…

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Why you'd press play

You want a mission that treats the universe's large-scale structure like a cosmic fingerprint.

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