skip to content

Kavli Institute for Cosmology, Cambridge

 

Why are the physical constants of the universe so perfect for life?

Tue, 24/06/2025 - 10:14

Conditions in our little pocket of the universe seem to be just right for life - and the much-debated anthropic principle forces us to wonder why

Cosmic signal from the very early universe will help astronomers detect the first stars

Fri, 20/06/2025 - 11:53

Now, an international group of astronomers led by the University of Cambridge have shown that we will be able to learn about the masses of the earliest stars by studying a specific radio signal – created by hydrogen atoms filling the gaps between star-forming regions – originating just a hundred million years after the Big Bang.

By studying how the first stars and their remnants affected this signal, called the 21-centimetre signal, the researchers have shown that future radio telescopes will help us understand the very early universe, and how it transformed from a nearly homogeneous mass of mostly hydrogen to the incredible complexity we see today. Their results are reported in the journal Nature Astronomy.

“This is a unique opportunity to learn how the universe’s first light emerged from the darkness,” said co-author 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 study of the universe’s most ancient stars hinges on the faint glow of the 21-centimetre signal, a subtle energy signal from over 13 billion years ago. This signal, influenced by the radiation from early stars and black holes, provides a rare window into the universe’s infancy.

Fialkov leads the theory group of REACH (the Radio Experiment for the Analysis of Cosmic Hydrogen). REACH is a radio antenna and is one of two major projects that could help us learn about the Cosmic Dawn and the Epoch of Reionisation, when the first stars reionised neutral hydrogen atoms in the universe.

Although REACH, which captures radio signals, is still in its calibration stage, it promises to reveal data about the early universe. Meanwhile, the Square Kilometre Array (SKA)—a massive array of antennas 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 the current study, Fialkov – who is also a member of the SKA – and her collaborators developed a model that makes predictions for the 21-centimetre signal for both REACH and SKA, and 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-centimetre signal of 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, who is also a member of Cambridge’s Kavli Institute for Cosmology. “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.”

In developing their theoretical model, the researchers studied how the 21-centimetre signal reacts to the mass distribution of the first stars, known as Population III stars. They found that previous studies have underestimated this connection as they did not account for the number and brightness of X-ray binaries – binary systems made of a normal star and a collapsed star – among Population III stars, and how they affect the 21-centimetre signal.

Unlike optical telescopes like the James Webb Space Telescope, which capture vivid images, radio astronomy relies on statistical analysis of faint signals. REACH and SKA will not be able to image individual stars, but will instead 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 we are reporting have huge implications for our understanding of the nature of the very first stars in the Universe,” said co-author Dr Eloy de Lera Acedo, Principal Investigator of the REACH telescope and PI at Cambridge of the SKA development activities. “We show evidence that our 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 we are doing 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). Anastasia Fialkov is a Fellow of Magdalene College, Cambridge. Eloy de Lera Acedo is an STFC Ernest Rutherford Fellow and a Fellow of Selwyn College, Cambridge.

 

Reference:
T. Gessey-Jones et al. ‘Determination of the mass distribution of the first stars from the 21-cm signal.’ Nature Astronomy (2024). DOI: 10.1038/s41550-025-02575-x

Understanding how the universe transitioned from darkness to light with the formation of the first stars and galaxies is a key turning point in the universe’s development, known as the Cosmic Dawn. However, even with the most powerful telescopes, we can’t directly observe these earliest stars, so determining their properties is one of the biggest challenges in astronomy.

This is a unique opportunity to learn how the universe’s first light emerged from the darknessAnastasia FialkovESA/Webb, NASA, ESA, CSAThe image shows a deep galaxy field, featuring thousands of galaxies of various shapes and sizes


The text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright ©University of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

YesLicence type: Attribution

The radical idea that space-time remembers could upend cosmology

Tue, 17/06/2025 - 11:45

There are new hints that the fabric of space-time may be made of "memory cells" that record the whole history of the universe. If true, it could explain the nature of dark matter and much more

Clustering pattern of dwarf galaxies not predicted by models of cosmic structure formation

Thu, 05/06/2025 - 09:53

Nature, Published online: 04 June 2025; doi:10.1038/d41586-025-01699-4

A surprising pattern of spatial distribution was discovered in dwarf galaxies, whereby diffuse ones cluster more strongly than do compact ones — opposite to the trend seen in massive galaxies. This finding challenges standard models of the formation of galactic structures, calling for theories about the assembly of visible- and dark-matter structures to be revised.

Why it's taking a century to pin down the speed of the universe

Wed, 04/06/2025 - 10:09

The Hubble constant, a set number that connects a galaxy’s speed to its distance from Earth and tells us how fast the universe is expanding, was first described more than a hundred years ago – but astronomers have debated it ever since

A photon caught in two places at once could destroy the multiverse

Mon, 26/05/2025 - 17:28

The idea of a multiverse of universes is derived from a particular interpretation of quantum mechanics, but now a new twist on a classic experiment says it is time to put the idea to bed

Physicists are waging a cosmic battle over the nature of dark energy

Mon, 26/05/2025 - 17:28

Results from the Dark Energy Spectroscopic Instrument (DESI) suggest that dark energy, a mysterious force in the universe, is changing over time. This would completely re-write our understanding of the cosmos - but now other physicists are challenging this view

Large gas inflow driven by a matured galactic bar in the early Universe

Thu, 22/05/2025 - 08:34

Nature, Published online: 21 May 2025; doi:10.1038/s41586-025-08914-2

Gas distribution and motion patterns driven by a galactic bar of the J0107a dusty star-forming galaxy have analogues in local bars, indicating that similar processes of active star formation were already operating 11.1 billion years ago.

Earliest galaxy ever seen offers glimpse of the nascent universe

Wed, 21/05/2025 - 09:54

The galaxy MoM-z14 dates back to 280 million years after the big bang, and the prevalence of such early galaxies is puzzling astronomers

How dark energy findings may inspire a new generation of physics nerds

Fri, 16/05/2025 - 10:05

The discovery of the cosmic acceleration problem truly inspired me as a teenage physics nerd. Recent, related revelations about dark energy will hopefully capture the interest of today’s young science geeks, says Chanda Prescod-Weinstein

Scientists in a race to discover why the Universe exists

Tue, 13/05/2025 - 10:07

Researchers in the US and Japan are racing to build new particle detectors that they hope will explain why the Universe exists.

Why physicists keep trying to get rid of space-time entirely

Wed, 07/05/2025 - 10:01

Physicists are trying to ditch the concept of space-time – the supposed fabric of physical reality. Quantum columnist Karmela Padavic-Callaghan explains why

Dark energy bombshell sparks race to find a new model of the universe

Sat, 03/05/2025 - 18:38

‘Shocking’ results from a major astronomical study have raised doubts about the standard model of cosmology, forcing scientists to consider new ways of understanding dark energy and gravity

The 'impossible' particle hinting at the universe's biggest secrets

Tue, 29/04/2025 - 10:23

Neutrinos have always been hard to explain – and now the detection of one so energetic it shouldn't exist may help illuminate the strangest corners of the cosmos

‘Dark matter’, 'Big Bang' and ‘spin’: how physics terms can confuse researchers

Wed, 23/04/2025 - 10:32

Nature, Published online: 22 April 2025; doi:10.1038/d41586-025-01089-w

In episode three of What's in a name we look at how ideas can be lost in translation when physicists try to name the unknown.

Top quarks spotted at mega-detector could reveal clues to early Universe

Fri, 11/04/2025 - 14:25

Nature, Published online: 10 April 2025; doi:10.1038/d41586-025-01075-2

Heaviest known elementary particles and their antimatter counterparts are detected after nuclear smash-ups at the Large Hadron Collider.

FAST Drift Scan Survey for HI Intensity Mapping. II. Stacking-based Beam Construction of the 19-feed Array at $1.4$ GHz

Thu, 10/04/2025 - 10:27
arXiv:2412.02582v2 Announce Type: replace Abstract: Neutral hydrogen (HI) intensity mapping (IM) presents great promise for future cosmological large-scale structure surveys. However, a major challenge for HIIM cosmological studies is to accurately subtract the foreground contamination. An accurate beam model is crucial for improving the quality of foreground subtraction. In this work, we develop a stacking-based beam reconstruction method utilizing the radio continuum point sources within the drift-scan field. Based on the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we employ two sets of drift-scan survey data and merge the measurements to construct the beam patterns of the 19 FAST L-band feeds. To model the beams, we utilize the Zernike polynomial (ZP), which effectively captures asymmetric features of the main beam and the different side lobes. Due to the symmetric location of the beams, the main features of the beams are closely related to the distance from the center of the feed array, e.g., as the distance increases, side lobes become more pronounced. This modeling pipeline leverages the stable drift-scan data to extract beam patterns while accounting for and excluding the reflector's changing effects. It provides a more accurate measurement beam and a more precise model beam for FAST HIIM cosmology surveys.

Space could emerge from time

Wed, 09/04/2025 - 10:29

An investigation of the changing behaviour of a single quantum bit through time has uncovered a tantalising similarity to the geometry of three-dimensional space

How nothing could destroy the universe

Wed, 02/04/2025 - 09:21

The concept of nothing once sparked a 1000-year-long war, today it might explain dark energy and nothingness even has the potential to destroy the universe, explains physicist Antonio Padilla

BBC Inside Science

Fri, 28/03/2025 - 11:52

How a ‘dark energy’ experiment could upend Einstein's theory of the universe.