The universe’s transition from darkness to light was a pivotal moment in its development, known as the Cosmic Dawn. However, despite the most powerful telescopes, we cannot directly observe these earliest stars. This makes determining their properties one of the biggest challenges in astronomy.

An international team of astronomers led by the University of Cambridge has made significant progress in understanding how the first stars and their remnants affected a specific radio signal – the 21-centimeter signal – created by hydrogen atoms filling the gaps between star-forming regions, just a hundred million years after the Big Bang.

By studying this signal, researchers have shown that future radio telescopes will be able to learn about the masses of the earliest stars. Their results were reported in the journal Nature Astronomy.

“This is a unique opportunity to learn how the universe’s first light emerged from the darkness,” said Professor Anastasia Fialkov from Cambridge’s Institute of Astronomy. “The transition from a cold, dark universe to one filled with stars is a story we’re only beginning to understand.”

The 21-centimeter signal provides a rare window into the universe’s infancy. It is influenced by the radiation from early stars and black holes. Researchers have found that this signal is sensitive to the masses of first stars.

Fialkov leads the theory group of REACH (the Radio Experiment for the Analysis of Cosmic Hydrogen). REACH is a radio antenna still in its calibration stage but promises to reveal data about the early universe. The Square Kilometre Array (SKA), under construction, will map fluctuations in cosmic signals across vast regions of the sky.

Both projects are vital in probing the masses, luminosities, and distribution of the universe’s earliest stars. In this study, Fialkov and her collaborators developed a model that makes predictions for the 21-centimeter signal for both REACH and SKA. They found that the signal is sensitive to the masses of first stars.

“We are the first group to consistently model the dependence of the 21-centimeter signal on the masses of the first stars, including the impact of ultraviolet starlight and X-ray emissions from X-ray binaries produced when the first stars die,” said Fialkov. “These insights are derived from simulations that integrate the primordial conditions of the universe, such as the hydrogen-helium composition produced by the Big Bang.”

Radio astronomy relies on statistical analysis of faint signals, unlike optical telescopes like the James Webb Space Telescope, which capture vivid images. REACH and SKA will not be able to image individual stars but will provide information about entire populations of stars, X-ray binary systems, and galaxies.

“It takes a bit of imagination to connect radio data to the story of the first stars, but the implications are profound,” said Fialkov.

The predictions made in this study have huge implications for understanding the nature of the very first stars in the universe. Researchers show evidence that their radio telescopes can tell us details about the mass of those first stars and how these early lights may have been very different from today’s stars.

Radio telescopes like REACH are promising to unlock the mysteries of the infant Universe, and these predictions are essential to guide the radio observations being done from the Karoo in South Africa. The research was supported in part by the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

The recent study by a team of solar physicists has provided unprecedented insight into the fine-scale structure of the Sun’s surface. Using the powerful U.S. National Science Foundation (NSF) Daniel K. Inouye Solar Telescope on Maui, scientists have observed ultra-narrow bright and dark stripes on the solar photosphere for the first time in such high detail. These stripes, called striations, are the result of curtain-like sheets of magnetic fields that ripple and shift like fabric blowing in the wind.

As light from the hot granule walls passes through these magnetic “curtains,” the interaction produces a pattern of alternating brightness and darkness that traces variations in the underlying magnetic field. If the field is weaker in the curtain than in its surroundings, it appears dark; if it’s relatively stronger, it appears bright.

The researchers used the Inouye Solar Telescope’s Visible Broadband Imager (VBI) instrument operating in the G-band, a specific range of visible light that highlights areas with strong magnetic activity. This setup allowed them to observe the solar photosphere at an impressive spatial resolution better than 0.03 arcseconds, which is the sharpest ever achieved in solar astronomy.

The study confirms that these striations are signatures of subtle but powerful magnetic fluctuations – variations of only a hundred gauss – that alter the density and opacity of the plasma, shifting the visible surface by mere kilometers. These shifts, known as Wilson depressions, are detectable thanks to the unique resolving power of the 4-meter primary mirror of the NSF Inouye Solar Telescope.

Studying the magnetic architecture of the solar surface is essential for understanding the most energetic events in the Sun’s outer atmosphere – such as flares, eruptions, and coronal mass ejections – and improving space weather predictions. This discovery not only enhances our understanding of this architecture but also opens the door to studying magnetic structures in other astrophysical contexts – and at small scales once thought unachievable from Earth.

The findings were published in The Astrophysical Journal Letters under the title “The striated solar photosphere observed at 0.03” resolution.”

The Apollo astronauts stumbled upon an unexpected treasure on the lunar surface – tiny, bright orange glass beads that had been frozen in time for billions of years. These minuscule, 1mm-wide capsules hold secrets about the moon’s explosive past, revealing a chapter of volcanic eruptions that shaped the satellite’s history.

Researchers led by Thomas Williams, Stephen Parman, and Alberto Saal from Brown University, in collaboration with WashU scientists, have employed cutting-edge techniques to study these ancient artifacts. Using instruments like NanoSIMS 50, atom probe tomography, scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy, they have gained unprecedented insights into the surface of the beads.

Each glass bead is a testament to the moon’s volcanic activity, where lava droplets solidified instantly in the cold vacuum surrounding the satellite. The colors, shapes, and chemical compositions of these tiny minerals are unlike anything found on Earth, serving as probes into the pressure, temperature, and chemical environment of lunar eruptions 3.5 billion years ago.

The study reveals that the style of volcanic eruptions changed over time, much like reading the journal of an ancient lunar volcanologist. These findings not only shed light on the moon’s past but also demonstrate the importance of preserving samples for future generations, as technology advances and new instruments become available to uncover hidden secrets.