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This is QSO1. The James Webb Space Telescope first spotted it in 2023. It’s one of hundreds of similar objects known as “little red dots” that the telescope has seen in the early universe. It's very unusual to find a population of sources where we're just left scratching your head and wondering, what is this thing that we're looking at? We are all working together to try and uncover the mysteries of the early universe, the mysteries of these little red dots.
For the past two years, researchers have trained the Webb telescope on various little red dots, capturing their light across a spectrum of wavelengths. They are characterized by a sort of v-shape in the spectra energy distribution. This is indication that we have gas that is moving at very high velocity around something. In 2025, a team of researchers confirmed the identity of QSO1: a supermassive black hole as heavy as 50 million suns, basically alone in the early cosmos. The exceptional finding here is that we essentially find no trace of a galaxy around this black hole. It’s really extraordinary that the universe managed to make these monsters without much of anything else around them. So this is really a fantastic new discovery.
The first clues about QSO1’s nature arose from a direct measurement of its mass — an unprecedented feat for a black hole in the early universe. The results challenge our understanding of how black holes form and threaten to rewrite our assumptions about the history of the universe. We know that nearly every galaxy has a supermassive black hole at their center. But even if these are supermassive, they still make a tiny fraction of the overall mass of the entire galaxy in which they are hosted. Typically, they are a thousand times less massive than their host galaxy. QSO1 clocked in at nearly two-thirds of the mass of the surrounding material. To see such a black hole that basically dominates the total mass in this way is very unusual – meaning there's very little stuff around it. And so some people say that this is almost naked – although we see, of course, some gas, otherwise you would not be able to observe the black hole at all.
When researchers analyzed the gas orbiting QS01, they found only hydrogen and helium, the elements produced by the Big Bang. So it looks like it's primordial gas – it's not very enriched. Stars forge heavier elements as they live and die. The lack of these elements suggests that QSO1 grew into a supermassive black hole before nearby stars existed — a surprising inversion of the usual story, where galaxies were thought to give rise to the black holes at their centers. So it’s a paradigm shift in terms of our understanding of black holes and galaxies.
These little red dots are the progenitors of today's supermassive black holes. And the question is, where did they originate from? One leading idea, known as the “heavy seed” scenario, suggests that the first black holes in the early universe formed directly from the collapse of enormous gas clouds. But the most exciting possibility dates back to a 1971 proposal from Stephen Hawking: that black holes arose in the primordial soup of the Big Bang itself. And in this case, black holes will be the first things forming the universe well before stars, well before galaxies – and so they wait for some gas to swirl around them to actually be visible. I think none of the theories that we currently have can fully explain these observations. And that's great because it means that there is more for us to learn about this.
In the next few years, Webb will continue to gather data on little red dots. But astronomers are particularly excited about LISA, a future space mission that will use lasers to detect gravitational waves from some of the most massive and distant events in the cosmos. We can go and actually take observations and try to prove or disprove the theories about the little red dots. This is basically the fundamental scientific method at play: we've got something new, folks are putting out proposals about what they think they are, and then observers are going out and testing those predictions. And so it's kind of very fundamental science.
In April 2024, a collaboration of nearly a thousand astrophysicists announced a startling result: dark energy, the mysterious force long credited with driving the expansion of the universe, may be weakening. Using the Dark Energy Spectroscopic Instrument, known as DESI, the team mapped the precise positions and motions of more than six million galaxies. The early results were thrilling, but the researchers were cautious. When it first came out in 2024, there was a lot of skepticism. And of course, it's our job to be skeptical. But in 2025, with three years of DESI observations, a vastly expanded map of fifteen million galaxies, and two additional independent datasets, those hints are hardening into something more conclusive. When we previously were considering the original signal that was observed, it was entirely possible that a newer, bigger data set, especially when that's three times as large, could just result in the signal disappearing. And it hasn't. If dark energy is evolving, it would upend cosmologists’ understanding of the universe. For the first time in 27 years, we have some new numbers, new properties of dark energy to work with. This is like a dream come true for a theorist.
In the late nineties, researchers found that something appeared to be speeding up the expansion of the universe. The observations fit neatly with Albert Einstein’s hypothesis about a cosmological constant, an unchanging dark energy that permeates empty space. This hypothesis is the basis of Lambda-CDM, cosmologists’ current model of the universe. But the DESI results are throwing it into question. DESI measures subtle imprints of ancient sound waves, known as baryon acoustic oscillations, or BAOs, that rippled through the early universe. As the universe expands, the distances marked by these BAOs stretch with it. And that stretching then tells us about how the universe is expanding. DESI’s first survey hinted that the BAO scale wasn’t growing at a constant rate – the cosmic expansion appeared to be slowing. Then, on March 19, 2025, the team released a much larger data set, adding supernova observations and measurements of the cosmic microwave background, the faint afterglow of the Big Bang. Taken together, the evidence made the slowdown even harder to dismiss. It was actually a remarkable effort to process all of that data so rapidly. And what they end up with is about three times as many galaxies as they had in their first data release. And the signal for this evolving or thawing dark energy still seems to hold. The same day, another team of cosmologists, the Dark Energy Survey, backed up DESI’s findings. We're now at the point where we have multiple data sets pointing in the same direction. And so you can poke a hole in one, but you're still left with two others that point us towards this evolving dark energy.
To claim a discovery, physicists must prove a five-sigma level of confidence – about a one-in-a-million probability that the findings are a result of random chance. The previous data sets had achieved a probability of 3.5 sigma – about a one-in-300 chance that it's a statistical fluke. With DESI’s newest data set, that probability has ticked up to 4.2 sigma – a one-in-30,000 chance. Great claims require great evidence, and we're just not there yet because we’re not at the holy grail of five sigma. Researchers across the collaborations are reexamining the data to test whether any assumptions in their analysis could be skewing the results. But if indeed dark energy is evolving, the next step is to figure out exactly, “why is it evolving?” And then, “what exactly is it?” It could be also that it has nothing to do with the form of energy, but it's rather a modification to general relativity of Einstein at cosmological scales. But my personal thought is that this might be an indication that we are putting the pieces together not in the right way. It could be something completely new. Researchers agree: it’s a thrilling time to be a cosmologist. And the best hope for pinning down whether dark energy is evolving may come from the next generation of powerful telescopes, especially the Vera Rubin Observatory. It’s absolutely incredible. It’s a whole new observatory. We’re gonna get hundreds of thousands of supernovae, which is orders of magnitude more than we’ve had up until this point. And that is just going to be a firehose of new data. Pandora's box is open to try to understand the universe. This might change completely cosmology. Like, in the same way that it happened 100 years before, at the time of Einstein. This is incredibly exciting. It is tantalizingly close to a paradigm shift in cosmology, and that's something that we feel may be necessary for us to really get to the bottom of what dark energy and dark matter are.
Plate tectonics was one of the great scientific revolutions of the 20th century, transforming our understanding of Earth from a solid rock into an active engine. This was an enormous revelation. Earth is an incredibly dynamic place. Just under the Earth’s surface, the mantle slowly churns rock, driving volcanoes and the motion of continents. Below it, the outer core forms a molten metal ocean. For decades, many scientists believed a sharp boundary separated these realms. But in 2025, independent investigations into volcanic rocks and vast, blob-like structures deep within Earth suggest that the core and mantle may be interacting. Earth's core is full of mysteries. These results have raised all sorts of questions about the core-mantle boundary. These questions point to the immense structures 3,000 kilometers below Earth’s surface. We see them very clearly in seismic images. There are these two massive regions the size of continents at the base of the mantle. What we know is that these two regions have low velocity. Scientists use seismic waves from earthquakes to probe Earth’s interior. Because waves slow down in the blob-like regions, scientists call them Large Low Shear Velocity Provinces, or LLSVPs. We are puzzled by what they are. We only know that seismic waves slow down there.
Arwen Deuss and her team at Utrecht University pored through seismic data from more than 100 earthquakes strong enough to reverberate through the LLSVPs and the surrounding mantle. We wanted to look at how much energy the waves lose when they travel through these regions. As a wave passes through rock, it can lose energy, or dampen, because the rock is hotter than the surrounding material. Scientists long assumed the heat of LLSVPs would dampen seismic waves. And so we started measuring that. And to our surprise, we actually found that these two LLSVP regions had very little damping. So waves didn't lose any energy when they travel through these regions. So, totally opposite to what we were expecting. Instead of damping as they passed through the blobs, the waves retained their strength. This told the researchers about the size of the crystalline grains in the LLSVPs. Small grains weaken waves, while large grains let them pass more easily. When we did some calculations, we realized that if those LLSVPs have really big grain sizes, even though they're hot, the waves will not lose much energy. And when we realized that, actually, stuff fell into place. How can you get a bigger grain size? Well, that happens over time. If you leave material in the mantle, then over time, the grain size will grow and grow and grow. So this also means that because the LLSVPs have a bigger grain size, they must be really old.
In January 2025, the group published their findings, suggesting that the LLSVPs are ancient reservoirs that preserve material from Earth’s formation. Just months later, more clues about Earth's interior emerged from a group studying the isotopes, or distinct forms, of the elements in volcanic rocks. Every process these rocks go through, they leave sort of like an isotopic fingerprint. And then by measuring these isotopes, you can partly resolve the history of these rocks. The team focused on ruthenium, a rare metal with a strong preference for bonding with iron rather than rock. We have one big iron reservoir – one big iron blob in our Earth – which is the Earth's core. During Earth’s formation, the ruthenium-100 isotope would have followed iron to the core, leaving the mantle depleted. Any ruthenium added later would have a different isotopic makeup. If the researchers found ruthenium-100 in volcanic rocks, it would point to material leaked from the core – likely rising through the LLSVPs. That would basically be the eureka moment. We actually got it. It is almost like a smoking-gun evidence.
Together, the two discoveries hint at a more connected deep Earth, where the core and mantle interact and the LLSVPs help shape mantle convection, the engine of plate tectonics. So I think these blobs are like big stable anchors. And we have the plates moving around and we have mantle convection, but it's all being organized around these kind of two big anchors that are sitting at the base of the mantle. Understanding plate tectonics is key to understanding why Earth is geologically alive – and why that matters for life itself. Why do we have life on Earth and not on Mars? Mars has very ancient parts everywhere, and a mantle that just hasn't been moving. And when you don't move the mantle and you don't have the plates, it's really difficult to keep the temperature stable and to make a planet stable enough for life to appear. So Mars is basically a dead planet, but Earth is very much alive. This geologically active planet actually helps us to live here.