The odds of finding such an event are less than one in a million.
For decades, humanity has held two incompatible answers to one of its deepest questions — how fast is the universe expanding? — and neither answer has yielded to the other. Now, a supernova ten billion light-years away, its light bent into five ghostly copies by the gravity of intervening matter, offers a third path: an independent measurement that owes nothing to the assumptions burdening either side. The cosmos, it seems, has quietly arranged a rare arbitration of its own.
- Two competing methods for measuring cosmic expansion have produced irreconcilable numbers for years, and the gap is too large for statisticians to dismiss as noise.
- Each method carries its own hidden fragility — one compounds small early errors across billions of light-years, the other rests on untestable assumptions about the universe's first moments.
- A supernova ten billion light-years away defied odds of less than one in a million by appearing as five distinct images, its light split by a gravitational lens into separate paths that each took a different amount of time to arrive.
- Those time delays between the five images can be used to calculate the Hubble constant through a method entirely independent of both existing approaches — no accumulated errors, no Big Bang assumptions.
- Astronomers have not yet completed the calculation, but the scientific community is energized: this single rare observation could break a deadlock that has unsettled cosmology for a generation.
Cosmologists have spent years wrestling with a stubborn contradiction at the heart of their field. Two well-established methods for measuring how fast the universe is expanding keep returning incompatible answers. The first, the cosmic distance ladder, uses the known brightness of nearby stars to build outward across ever-greater distances, arriving at a Hubble constant between 70 and 76 kilometers per second per megaparsec. The second reads the ancient microwave radiation left over from the Big Bang and calculates a value of 67 to 68. The gap is small in absolute terms but statistically impossible to dismiss — and both methods have genuine weaknesses that make the disagreement difficult to resolve from within.
In 2025, an extraordinary object entered the picture. Supernova SN 2025wny, located ten billion light-years away, is a superluminous explosion shining with the combined force of up to a hundred ordinary supernovas. More remarkably, its light passed through a massive gravitational lens on the way to Earth, bending spacetime and splitting the supernova's image into five separate copies — an event with odds of less than one in a million.
Each of those five images traveled a slightly different path through space, arriving at Earth at slightly different times. Those time delays are the key. By measuring them precisely, astronomers can calculate the Hubble constant through a method that neither builds on a chain of compounding measurements nor depends on assumptions about the universe's infancy. It stands alone. The calculation is still underway, but the potential is clear: this accidental alignment of a dying star and a cosmic lens may finally resolve one of the most consequential disagreements in modern science — and in doing so, sharpen our picture of the universe's age, composition, and fate.
Cosmologists have been stuck on a stubborn disagreement for years now, one that cuts to the heart of how we understand the universe itself. Two different ways of measuring how fast the cosmos is expanding keep producing incompatible answers, and neither side is wrong in any obvious way. The tension has become known simply as the Hubble tension, named after Edwin Hubble, who in the early twentieth century realized that galaxies were not stationary but racing away from each other at speeds that increased with distance.
The first measurement method, called the cosmic distance ladder, works by comparing nearby stars of known brightness with how bright they appear from Earth. By establishing distances to closer galaxies with confidence, astronomers then use that foundation to measure progressively more distant ones, using supernovas and variable stars as cosmic mile markers. This approach yields a Hubble constant between 70 and 76 kilometers per second per megaparsec—a unit of distance spanning about 3.26 million light-years. The second method analyzes the cosmic microwave background, the ancient radiation left over from the Big Bang itself that fills all of space. Using this radiation and our best theories about how the early universe behaved, scientists calculate a Hubble constant of 67 to 68 kilometers per second per megaparsec. The gap between these numbers is small in absolute terms but large enough that statisticians cannot explain it away as random error. Both methods have vulnerabilities. The cosmic distance ladder compounds any small mistakes made at the beginning, amplifying them across billions of light-years. The CMB method depends entirely on assumptions about the universe's infancy—assumptions that are difficult or impossible to test.
Then, in 2025, astronomers spotted something extraordinary: a supernova designated SN 2025wny, located 10 billion light-years away. This was no ordinary stellar explosion. It was a superluminous supernova, meaning it shines with the brightness of up to 100 typical supernovas combined. But the truly remarkable feature was that its light, traveling toward Earth, passed through a gravitational lens—a massive concentration of matter that bent spacetime itself, splitting the supernova's image into five separate copies. The odds of finding such an event are less than one in a million. Yet there it was.
What makes this discovery potentially transformative is the geometry of the situation. Each of the five images took a slightly different path through space to reach us, which means each one arrived at a different time. By measuring those time delays, astronomers can calculate the Hubble constant using a method that avoids the pitfalls of both existing approaches. It is a single, independent measurement rather than a chain of measurements that could accumulate errors. And it requires no assumptions about what happened in the first moments after the Big Bang. The calculation has not yet been completed, but the possibility of finally breaking the deadlock has energized the field. What emerges from this rare cosmic accident could reshape our understanding of how fast the universe is expanding and, by extension, how old it is and what it is made of.
Citações Notáveis
The measurement makes no assumptions about the early universe, avoiding weaknesses of both existing methods— Source material on the gravitational lens method
A Conversa do Hearth Outra perspectiva sobre a história
Why does it matter so much whether the Hubble constant is 70 or 68? Isn't that close enough?
The difference seems small, but it compounds across the entire history of the universe. It changes how old we think the cosmos is, what fraction of it is dark matter versus dark energy, and whether our best theories actually work. When two independent methods disagree this persistently, it usually means something fundamental is wrong with one of them—or both.
And this supernova with five images solves that problem how?
It gives us a third way to measure, one that doesn't inherit the weaknesses of the other two. The time delays between the images are like a cosmic clock. You measure them, you do the math, and out comes the Hubble constant. No chain of assumptions, no accumulated errors from measuring nearby galaxies first.
How rare is this, really?
Less than one in a million. Supernovas are already uncommon. Gravitational lenses are uncommon. The odds of both happening to the same explosion, at a distance where we can measure it, are vanishingly small. The fact that it happened at all feels almost like luck.
So what happens next?
Astronomers finish the calculation. They publish the result. And then we find out whether the universe has been telling us the truth all along, or whether we've been misunderstanding something fundamental about how it works.