Posted on 09/17/2025 8:08:10 AM PDT by Red Badger
A rare cosmic configuration: An Einstein Cross with five points of light, instead of the usual four, has been discovered by scientists. (Credit: Nicolás Lira Turpaud (ALMA Observatory) & adapted from Cox et al. 2025)
Brightest Glimpse Yet Of Dark Matter Comes From Rare Cosmic Lens
In A Nutshell
* Astronomers discovered HerS-3 forming a rare Einstein Cross with five images instead of four.
* Computer models required a hidden dark matter halo of 1.6–10 trillion solar masses to explain the pattern.
* The galaxy is magnified 17–19 times, revealing rapid star formation and high-speed gas outflows.
* This is the first Einstein Cross seen at submillimeter wavelengths and the first to include a central fifth image.
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PARIS — A team of international astronomers have identified a cosmic oddity unlike anything seen before: a galaxy bent by gravity into an Einstein Cross with not four but five distinct images. To explain this unusual geometry, researchers concluded that a massive invisible structure — a dark matter halo weighing about a trillion times the Sun — must be present.
What Is an Einstein Cross?
Einstein predicted that massive objects bend space and time, deflecting the light of more distant sources. When the alignment is nearly perfect, the background object may appear as four bright spots arranged in a cross. These so-called Einstein Crosses are rare cosmic events that act like natural magnifying glasses, letting astronomers see distant galaxies in much greater detail than normal telescopes allow.
The case of HerS-3 breaks this pattern entirely. This dusty, star-forming galaxy appears as it was about 11.5 to 12 billion years ago, when the universe was less than a quarter of its present age. Observations with multiple telescopes detected not only the expected four images but also a faint fifth at the center of the cross.
The discovery wasn’t a fluke. Independent measurements with specialized telescopes in France and Chile confirmed the same fivefold pattern. Each image displayed identical chemical signatures in their light spectra, proving they came from the same galaxy.
This system marks the first time an Einstein Cross has been detected at submillimeter wavelengths, and the first time such a cross has included a central fifth image.
How Did Computer Models Reveal a Hidden Halo?
Explaining this arrangement required more than the four visible galaxies in front of HerS-3. Computer models simulate how gravity bends light, essentially creating virtual laboratories to test different scenarios. When researchers fed in only the four visible galaxies, the models consistently failed to match what they observed in the sky.
The solution was to add another massive component southeast of the brightest foreground galaxy. Its location was calculated to be 25–60 kiloparsecs away, or about 80,000 to 200,000 light-years, yet no visible galaxy sits there.
That additional mass has no visible counterpart. Its presence is inferred entirely from how it bends light, like detecting an invisible person by watching their shadow. The best explanation is a dark matter halo, invisible to all telescopes, with a mass estimated between about 1.6 trillion and 10 trillion times the Sun.
With this halo included, the models accurately reproduced the shape, orientation, and brightness of all five images.
A Magnified Cosmic Fireworks Show
HerS-3 itself is putting on quite a show. Thanks to gravitational lensing acting like a cosmic magnifying glass, it appears 17 to 19 times brighter than it would naturally. This boost in brightness lets astronomers resolve details that would otherwise be impossible to detect.
The galaxy is creating stars at hundreds of times the rate of our Milky Way. Gas streams are rushing outward from its center at more than 350 kilometers per second, driven by powerful winds from massive stars that burn bright and die young.
The geometry of this cosmic lens is also unusual. The two brightest images are separated by 7.5 arcseconds, far wider than in most Einstein Crosses, which usually span only a few arcseconds.
Einstein Cross - The European Space Agency’s Faint Object Camera on board NASA’s Hubble Space Telescope provided astronomers with the most detailed image ever taken of the gravitational lens G2237 + 0305, sometimes referred to as the “Einstein Cross,” released on September 13, 1990. The photograph shows four images of a very distant quasar which has been multiple-imaged by a relatively nearby galaxy acting as a gravitational lens. The angular separation between the upper and lower images is 1.6 arcseconds. (Credit: NASA, ESA, and STScI)
Why This Discovery Matters
HerS-3 provides an exceptional natural laboratory. It lets scientists study both a young, dust-rich galaxy from the early universe and the hidden dark matter halo that shapes its lensing pattern. Systems like this help researchers map how dark matter is distributed throughout space, a question that has puzzled scientists for decades.
Although not the focus of this research, Einstein Crosses with multiple images also carry potential for measuring cosmic distances. Because the light paths differ slightly, any changes in the brightness of the background galaxy would appear at different times in each image—like watching the same firework explode through multiple mirrors. Measuring such delays could offer an independent method for calculating how fast the universe is expanding.
A First in Its Class
The HerS-3 discovery stands out for two reasons: it’s the first Einstein Cross identified at submillimeter wavelengths, and it’s the first to display a central fifth image. Both features make it a rare opportunity to probe the physics of how gravity bends light and study galaxies during a formative period in cosmic history.
Even a century after Einstein predicted gravitational lensing, the universe continues to deliver surprises. Dark matter has yet to be detected directly on Earth, but in the cosmos, its signature is unmistakable: invisible mass bending the path of light across billions of years. The HerS-3 system offers one of the clearest windows yet into this hidden framework that holds our universe together.
Paper Summary
Methodology
Researchers used multiple radio telescopes to study a distant galaxy called HerS-3, including the Northern Extended Millimeter Array (NOEMA) in France and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. They also used the Very Large Array in New Mexico and the Hubble Space Telescope for additional observations. When they noticed an unusual five-point lensing pattern instead of the expected four-point Einstein Cross, they created detailed computer models to understand what could cause this rare configuration. The team tested various scenarios using only the visible foreground galaxies, then systematically added different types of invisible mass distributions to see what could reproduce their observations.
Results
Analysis revealed that four visible galaxies at a redshift of approximately 1.0 were gravitationally lensing a more distant galaxy (HerS-3) at redshift 3.0607. However, models using only these visible galaxies could not explain the observed lensing pattern. Only by adding a massive dark matter halo—weighing about one trillion solar masses and located 25-60 kiloparsecs southeast of the brightest foreground galaxy—could researchers reproduce all five observed images. The background galaxy HerS-3 appears to be an intensely star-forming system with molecular gas outflows exceeding 350 kilometers per second, magnified by a total factor of 17-19 times by the gravitational lensing effect.
Limitations
The study’s conclusions depend heavily on computer modeling and assumptions about the dark matter halo’s properties, including its shape and internal structure. While the researchers tested both spherical and elliptical halo models with different density profiles, they cannot definitively determine the exact nature of the dark matter based on current observations alone. The team also notes that future higher-resolution observations will be needed to confirm their predictions about gas outflows and to further constrain the dark matter halo’s characteristics.
Funding and Disclosures
The research was supported by multiple international funding agencies, including the French National Research Agency (ANR), the Deutsche Forschungsgemeinschaft (DFG), the National Science Foundation (NSF), NASA, and various European institutions. The observations used data from facilities operated by IRAM, ESO, and NRAO. The authors declared no conflicts of interest related to this research.
Publication Information
This study was published in The Astrophysical Journal, Volume 991, Article 53, on September 20, 2025. The paper was authored by an international team led by Pierre Cox from the Institut d’Astrophysique de Paris, with significant contributions from researchers at institutions including Rutgers University, Chalmers University of Technology, and multiple European observatories. The research was received on March 5, 2025, revised on July 16, 2025, and accepted for publication on July 18, 2025.
Ping!........................
Real nice. Now everybody knows. It was hidden for a reason...
If it’s “Dark Matter”, why can I see it?.................
Uh, its daylight out. Can’t see it at night.
😁😂🤣😁...............................
The computer simulations show a way that an enormous amount of dark matter, shaped in exactly the correct way, could produce the visual effect we see.
Whether the computer simulation is correct, or if another, unknown phenomena is producing the effect, is unknown.
Got the same effect when I used an ointment in the eyes to get rid of dry eye affliction...
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