Air Showers Ruin Astrophotos, but They Could be a New Method for Studying the Universe

An example of a cosmic-ray extensive air shower recorded by the Subaru Telescope. The highlighted tracks, which are mostly aligned in similar directions, show the shower particles induced from a high-energy cosmic ray. Credit: NAOJ/Hyper Suprime-Cam (HSC) Collaboration

Cosmic rays are a fascinating and potentially hazardous phenomenon. These high-energy particles typically consist of protons that have been stripped of their electrons and accelerated to nearly the speed of light. When these rays collide with Earth’s atmosphere, an enormous amount of secondary particles known as an “air shower” results. Ordinarily, these showers are a source of frustration for astronomers since they leave “tracks” on telescope images that obscure the celestial objects (asteroids, stars, galaxies, exoplanets, etc.) being observed.

However, a research team from the National Astronomical Observatory of Japan (NAOJ) and Osaka Metropolitan University has found a new application for these energetic particles. Using a novel method, they could observe these extensive cosmic-ray air showers with unprecedented precision. The key to their method is the Subaru Prime Focus Camera (Suprime-Cam) mounted on the Subaru Telescope atop the Mauna Kea volcano in Hawaii. This method and the team’s findings could provide a new method for studying the Universe’s most energetic particles.

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Star Birth and Death Seen Near the Beginning of Time

An artist's illustration of the Universe's first stars, called Population 3 stars. Pop 3 stars would have been much more massive than most stars today, and would have burned hot and blue. Their lifetimes would've been much shorter than stars like our Sun. Credit: Wikimedia Commons

Until recently, astronomers could not observe the first stars and galaxies that formed in the Universe. This occurred during what is known as the “Cosmic Dark Ages,” a period that took place between 380,000 and 1 billion years after the Big Bang. Thanks to next-generation instruments like the James Webb Space Telescope (JWST), improved methods and software, and updates to existing observatories, astronomers are finally piercing the veil of this era and getting a look at how the Universe as we know it began.

This includes new observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, which obtained images of a stellar nursery inside a galaxy roughly 13.2 billion light-years away in the constellation Eridanus. This galaxy has a redshift value of more than 8.3, corresponding to when the Universe was less than 1 billion years old. The images discerned the sites of star formation and possible star death inside a nebula (MACS0416_Y1) located within this galaxy. This represents a major milestone for astronomy as this is the farthest distance such structures have been observed in our Universe.

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