SPACE/COSMOS
Dark energy seems to be changing, rattling our view of universe
AETHYR BY ANY OTHER NAME
By AFP
March 19, 2025
What if dark energy is not what we thought it was? This strange force could be weakening over time, observations suggest
Bénédicte Rey and Daniel Lawler
Dark energy, the mysterious force thought to be driving the ever-faster expansion of the universe, appears to be changing over time, according to new observations released Wednesday.
If dark energy is in fact weakening, it would likely mean that science’s understanding of how the universe works will need to be rewritten.
The new findings come from the Dark Energy Spectroscopic Instrument (DESI), which sits on a telescope at the Kitt Peak National Observatory in the US state of Arizona.
“What we are seeing is deeply intriguing,” said Alexie Leauthaud-Harnett, a spokesperson for the DESI collaboration which brings together 70 institutions across the world.
“It is exciting to think that we may be on the cusp of a major discovery about dark energy and the fundamental nature of our universe,” she said in a statement.
The DESI instrument’s thin optical fibres can simultaneously observe 5,000 galaxies or quasars — blazing monsters with a black hole at their heart — for 20 minutes.
This allows scientists to calculate the age and distance of these objects, and create a map of the universe so they can detect patterns and trace its history.
– ‘Tensions’ emerging –
Scientists have known for a century that the universe is expanding, because massive clusters of galaxies have been observed moving away from each other.
In the late 1990s, scientists shocked the field by discovering that the universe’s expansion has been speeding up over time.
The name dark energy was given to the phenomenon driving this acceleration, the effects of which seem to be partially offset by ordinary matter — and an also unknown thing called dark matter.
The universe is thought to be made of 70 percent dark energy, 25 percent dark matter — and just five percent normal matter.
Science’s best understanding of how the universe works, which is called the standard cosmological model, refers to dark energy as being constant — meaning it does not change.
The idea was first introduced by Albert Einstein in his theory of relativity.
Arnaud de Mattia, a French physicist involved in analysing the DESI data, told AFP that the standard model is “satisfactory” but some “tensions” are emerging between observations.
There are several different ways of measuring the expansion of the universe, including looking at the lingering radiation from after the Big Bang, exploding stars called supernovae and how gravity distorts the light of galaxies.
When the DESI team combined their new data with other measurements, they found “signs that the impact of dark energy may be weakening over time”, according to a statement.
“When we combine all the cosmological data, it favours that the universe’s expansion was accelerating at a slightly higher rate around seven billion years ago,” de Mattia said.
But for the moment there is “absolutely not certainty” about this, he added.
– ‘Inflection point’ –
French physicist Etienne Burtin was confident that “we should have a clearer picture within five years”.
This is because there is loads of new data expected from DESI, Europe’s Euclid space telescope, NASA’s upcoming Nancy Grace Roman space telescope and the Vera Rubin Observatory in Chile.
“This new generation of surveys — in the next few years — will nail this,” Joshua Frieman, a theoretical astrophysicist at the University of Chicago, told AFP.
But for now, “we’re at this interesting inflection point”, added Frieman, a dark energy expert and former DESI member.
Burtin said confirming the “evolving dark energy” theory would be a “revolution on the level of the discovery of accelerated expansion”, which itself was the subject of a physics Nobel.
“The standard cosmological model would have to be different,” he added.
The DESI research, which involved three years’ worth of observations of 15 million galaxies and quasars, was presented at a conference of the American Physical Society in California.
What is dark energy? One of science’s great mysteries, explained
By AFP
March 20, 2025
The truth is out there: Scientists hope to crack the case of dark energy in the next few years - Copyright AFP/File NICHOLAS KAMM, Handout
Daniel Lawler
Dark energy makes up roughly 70 percent of the universe, yet we know nothing about it.
Around 25 percent of the universe is the equally mysterious dark matter, leaving just five percent for everything that we can see and touch — matter made up of atoms.
Dark energy is the placeholder name scientists have given to the unknown force causing the universe to expand faster and faster over time.
But some recent cosmic clues have been chipping away at the leading theory for this phenomenon, which could eventually mean humanity will have to rethink our understanding of the universe.
And with several new telescopes taking aim at the problem, scientists hope to have some concrete answers soon.
Here is what you need to know about what many scientists have called the greatest mystery in the universe.
– So what is dark energy exactly? –
No one knows. It is invisible and it does not interact with matter or light.
And it may not even exist.
This story begins — like everything else — at the Big Bang around 13.8 billion years ago, when the universe first started expanding.
Since then, there has been “cosmic tug-of-war” between two mysterious forces, Joshua Frieman, a theoretical astrophysicist at the University of Chicago, told AFP.
Dark matter is thought to pull galaxies together, while dark energy pushes them apart.
During the first nine or so billion years of the universe, “dark matter was winning,” forming galaxies and everything else, Frieman said.
Then dark energy gained the upper hand, starting to speed up the expansion of the universe.
However for most of history, scientists had little idea this almighty tussle was going on. They thought that the expansion of the universe would simply start to slow down because of gravity.
Everything changed in 1998, when two separate groups of astronomers noticed that distant exploding stars called supernovae were farther away than they ought to be.
This led to the discovery that the universe is not just expanding — it is do so faster and faster.
So what could be causing this acceleration? They gave this strange force a name: dark energy.
– What are the main theories? –
The leading theory has long been that empty space itself produces dark energy.
Think of a cup of coffee, Frieman said.
“If I remove all the particles from the cup of coffee, there is still energy in there due to what we call the quantum vacuum,” he said.
This energy of empty space is known as the cosmological constant. It is the theory used in the standard model of cosmology, Lambda-CDM, which is our best guess for how the universe works.
But in recent years, several scientific results have appeared to support a rival theory — called evolving dark energy — which has brought the standard model into question.
On Wednesday, new results from the Dark Energy Spectroscopic Instrument provided the latest signs that dark energy could actually be weakening over time.
However the scientists behind the research emphasise there is not yet definitive proof.
If proven right, this would rule out that dark energy is a cosmological constant.
It could not be “the energy of empty space — because empty space doesn’t change,” explained Frieman, a leading proponent of the theory.
For dark matter to change, it would likely require the existence of some incredibly light, as-yet-unknown particle.
Another possibility is that there is something wrong with our calculations — or our understanding of gravity.
Einstein’s theory of relativity has withstood an incredible amount of scientific scrutiny over the last century, and has been proven right again and again.
There is no evidence that Einstein was wrong, but there is “a little bit of room” to change his theory when it comes to the largest scales of the universe, Frieman said.
– When could we know more? –
Soon. The best way to understand dark energy is to look at a vast swathe of sky, taking in as many galaxies with as much data as possible.
And a bunch of new telescopes are working to do just that.
On Wednesday, Europe’s Euclid space telescope released its first astronomical data since launching in 2023 — but any dark energy results are a couple of years away.
NASA’s Nancy Grace Roman space telescope, planned for launch in 2027, and the under-construction Vera Rubin Observatory in Chile will also take aim at the problem.
It is an exciting time for dark energy, Frieman said, adding that he expected a “definitive answer” in the next couple of years.
There is no time to waste, Frieman said.
“Every minute we wait, galaxies are disappearing from view.”
Oxygen discovered in most distant known galaxy
image:
This image shows the precise location in the night sky of the galaxy JADES-GS-z14-0, an extremely tiny dot in the Fornax constellation. As of today, this is the most distant confirmed galaxy we know of. Its light took 13.4 billion years to reach us and shows the conditions of the Universe when it was only 300 million years old. The inset of the image shows a close-up of this primordial galaxy as seen with the Atacama Large Millimeter/submillimeter Array (ALMA). The inset is overlaid on an image taken with the NASA/ESA/CSA James Webb Space Telescope.
When two research teams studied this galaxy with ALMA, operated by ESO and its international partners, they uncovered something unexpected: the spectrum of the galaxy indicated the presence of oxygen. This is the most distant detection of oxygen ever, and it defies what we knew about galaxy formation in the early Universe. The presence of heavy elements like oxygen suggest that these early galaxies evolved more rapidly than we thought. It is like finding an adolescent where you would only expect babies.
view moreCredit: ALMA (ESO/NAOJ/NRAO)/S. Carniani et al./S. Schouws et al/JWST: NASA, ESA, CSA, STScI, Brant Robertson (UC Santa Cruz), Ben Johnson (CfA), Sandro Tacchella (Cambridge), Phill Cargile (CfA)
Two different teams of astronomers have detected oxygen in the most distant known galaxy, JADES-GS-z14-0. The discovery, reported in two separate studies, was made possible thanks to the Atacama Large Millimeter/submillimeter Array (ALMA), in which the European Southern Observatory (ESO) is a partner. This record-breaking detection is making astronomers rethink how quickly galaxies formed in the early Universe.
Discovered last year, JADES-GS-z14-0 is the most distant confirmed galaxy ever found: it is so far away, its light took 13.4 billion years to reach us, meaning we see it as it was when the Universe was less than 300 million years old, about 2% of its present age. The new oxygen detection with ALMA, a telescope array in Chile’s Atacama Desert, suggests the galaxy is much more chemically mature than expected.
“It is like finding an adolescent where you would only expect babies,” says Sander Schouws, a PhD candidate at Leiden Observatory, the Netherlands, and first author of the Dutch-led study, now accepted for publication in The Astrophysical Journal. “The results show the galaxy has formed very rapidly and is also maturing rapidly, adding to a growing body of evidence that the formation of galaxies happens much faster than was expected."
Galaxies usually start their lives full of young stars, which are made mostly of light elements like hydrogen and helium. As stars evolve, they create heavier elements like oxygen, which get dispersed through their host galaxy after they die. Researchers had thought that, at 300 million years old, the Universe was still too young to have galaxies ripe with heavy elements. However, the two ALMA studies indicate JADES-GS-z14-0 has about 10 times more heavy elements than expected.
“I was astonished by the unexpected results because they opened a new view on the first phases of galaxy evolution,” says Stefano Carniani, of the Scuola Normale Superiore of Pisa, Italy, and lead author on the paper now accepted for publication in Astronomy & Astrophysics. “The evidence that a galaxy is already mature in the infant Universe raises questions about when and how galaxies formed.”
The oxygen detection has also allowed astronomers to make their distance measurements to JADES-GS-z14-0 much more accurate. “The ALMA detection offers an extraordinarily precise measurement of the galaxy’s distance down to an uncertainty of just 0.005 percent. This level of precision — analogous to being accurate within 5 cm over a distance of 1 km — helps refine our understanding of distant galaxy properties,” adds Eleonora Parlanti, a PhD student at the Scuola Normale Superiore of Pisa and author on the Astronomy & Astrophysics study [1].
“While the galaxy was originally discovered with the James Webb Space Telescope, it took ALMA to confirm and precisely determine its enormous distance,” [2] says Associate Professor Rychard Bouwens, a member of the team at Leiden Observatory. “This shows the amazing synergy between ALMA and JWST to reveal the formation and evolution of the first galaxies.”
Gergö Popping, an ESO astronomer at the European ALMA Regional Centre who did not take part in the studies, says: "I was really surprised by this clear detection of oxygen in JADES-GS-z14-0. It suggests galaxies can form more rapidly after the Big Bang than had previously been thought. This result showcases the important role ALMA plays in unraveling the conditions under which the first galaxies in our Universe formed."
Notes
[1] Astronomers use a measurement known as redshift to determine the distance to extremely distant objects. Previous measurements indicated that the galaxy JADES-GS-z-14-0 was at a redshift between about 14.12 and 14.4. With their oxygen detections, both teams have now narrowed this down to a redshift around 14.18.
[2] The James Webb Space Telescope is a joint project of NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA).
More information
This research was presented in two papers to appear in Astronomy & Astrophysics (https://aanda.org/10.1051/0004-6361/202452451) and The Astrophysical Journal.
The teams are composed of:
Italian-led, Astronomy & Astrophysics paper: Stefano Carniani (Scuola Normale Superiore, Pisa, Italy [SNS]), Francesco D’Eugenio (Kavli Institute for Cosmology, University of Cambridge, Cambridge, UK [CAM-KIC]; Cavendish Laboratory, University of Cambridge, Cambridge, UK [CAM-CavL] and INAF – Osservatorio Astronomico di Brera, Milano, Italy), Xihan Ji (CAM-KIC and CAM-CavL), Eleonora Parlanti (SNS), Jan Scholtz (CAM-KIC and CAM-CavL), Fengwu Sun (Center for Astrophysics | Harvard & Smithsonian, Cambridge, USA [CfA]), Giacomo Venturi (SNS), Tom J. L. C. Bakx (Department of Space, Earth, & Environment, Chalmers University of Technology, Gothenburg, Sweden), Mirko Curti (European Southern Observatory, Garching bei München, Germany), Roberto Maiolino (CAM-KIC, CAM-CavL and Department of Physics and Astronomy, University College London, London, UK [UCL]), Sandro Tacchella (CAM-KIC and CAM-CavL), Jorge A. Zavala (National Astronomical Observatory of Japan, Tokyo, Japan), Kevin Hainline (Steward Observatory, University of Arizona, Tucson, USA [UArizona-SO]), Joris Witstok (Cosmic Dawn Center, Copenhagen, Denmark [DAWN] and CAM-CavL), Benjamin D. Johnson [CfA], Stacey Alberts [UArizona-SO], Andrew J. Bunker (Department of Physics, University of Oxford, Oxford, UK [Oxford]), Stéphane Charlot (Sorbonne Université, CNRS, Institut d’Astrophysique de Paris, Paris, France), Daniel J. Eisenstein (CfA), Jakob M. Helton (UArizona-SO), Peter Jakobsen (DAWN and Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark), Nimisha Kumari (Space Telescope Science Institute, Baltimore, USA), Brant Robertson (Department of Astronomy and Astrophysics University of California, Santa Cruz, USA), Aayush Saxena (Oxford and UCL), Hannah Übler (CAM-KIC and CAM-CavL), Christina C. Williams (NSF NOIRLab, Tucson, USA), Christopher N. A. Willmer (UArizona-SO) and Chris Willott (NRC Herzberg, Victoria, Canada).
Dutch-led, The Astrophysical Journal paper: Sander Schouws (Leiden Observatory, Leiden University, Leiden, the Netherlands [Leiden]), Rychard J. Bouwens (Leiden), Katherine Ormerod (Astrophysics Research Institute, Liverpool John Moores University, Liverpool, United Kingdom [LJMU]), Renske Smit (LJMU), Hiddo Algera (Hiroshima Astrophysical Science Center, Hiroshima University, Hiroshima, Japan and National Astronomical Observatory of Japan, Tokyo, Japan), Laura Sommovigo (Center for Computational Astrophysics, Flatiron Institute, New York, USA), Jacqueline Hodge (Leiden), Andrea Ferrara (Scuola Normale Superiore, Pisa, Italy), Pascal A. Oesch (Département d’Astronomie, Université de Genève, Versoix, Switzerland; Cosmic Dawn Center, Copenhagen, Denmark and Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark), Lucie E. Rowland (Leiden), Ivana van Leeuwen (Leiden), Mauro Stefanon (Leiden), Thomas Herard-Demanche (Leiden), Yoshinobu Fudamoto (Center for Frontier Science, Chiba University, Chiba, Japan), Huub Rottgering (Leiden) and Paul van der Werf (Leiden).
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration for astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, Czechia, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as survey telescopes such as VISTA. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates ALMA on Chajnantor, a facility that observes the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society.
Links
- Research paper (Carniani et al.)
- Research paper (Schouws et al.)
- Photos of ALMA
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Astronomy and Astrophysics
DOI
NRL's narrow field imager launches on NASA's PUNCH mission
Naval Research Laboratory
WASHINGTON, D.C. — The U.S. Naval Research Laboratory’s (NRL) Narrow Field Imager (NFI) was launched into space aboard a SpaceX Falcon 9 rocket as a part of NASA’s Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission on March 11 and deployed from Falcon 9 on March 12.
PUNCH is a four-satellite constellation, collecting observations in low Earth orbit. It will conduct global, 3D observations of the inner heliosphere to investigate the solar corona's evolution into the solar wind. The mission is scheduled to conduct science for the next two years, following a 90-day commissioning period.
The NRL-developed NFI, sponsored by NASA, is a compact, externally occulted coronagraph. The external occulter blocks direct sunlight from entering the main optical aperture, which views the corona and starfield around the Sun using a compound lens system. Polarization is resolved using a polarizing filter wheel and the image is digitized using a CCD camera with a 2K x 2K active detector area.
NFI will image the transition of the Sun’s atmosphere to the solar wind to understand how the Sun generates the space plasma environment.
"The launch and deployment of NRL's Narrow Field Imager aboard the PUNCH mission marks a significant step forward in our ability to understand the dynamic processes that drive space weather," said NRL Coronal and Heliospheric Physics Section Head Robin Colaninno, Ph.D. "By imaging the transition of the Sun's atmosphere to the solar wind, we're gaining crucial insights that will ultimately improve our ability to predict and mitigate the impacts of these powerful events on Earth and in space."
Predicting the impact of space weather, from minor fluctuations to major coronal mass ejections (CMEs) and corotating interaction regions (CIRs), requires a comprehensive understanding of the solar wind. While originating at the Sun, these events evolve significantly on their journey to Earth, especially within the sparsely imaged region between the solar corona and inner heliosphere, posing a significant scientific challenge.
By capturing the evolution of coronal mass ejections (CMEs), PUNCH will provide scientists new data on their formation and propagation. This is essential for understanding and predicting these events, which can cause significant disruptions on Earth, including satellite damage, radio communication blackouts, and power grid failures. Enhanced predictions will also safeguard robotic explorers operating in interplanetary space.
About the U.S. Naval Research Laboratory
NRL is a scientific and engineering command dedicated to research that drives innovative advances for the U.S. Navy and Marine Corps from the seafloor to space and in the information domain. NRL, located in Washington, D.C. with major field sites in Stennis Space Center, Mississippi; Key West, Florida; Monterey, California, and employs approximately 3,000 civilian scientists, engineers and support personnel.
For more information, contact NRL Corporate Communications at (202) 480-3746 or nrlpao@nrl.navy.mil. Please reference package number at top of press release.
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