High in the dry air of Chile, a telescope has glimpsed a faint icy world drifting in the deep cold past Pluto, a place where the solar system thins into scattered remnants of its own making. Designated 2026 ED138, the body may one day be counted among the dwarf planets, but for now it hangs in a kind of suspended question, its size still a matter of honest uncertainty. Its discovery reminds us how much of the outer sky remains unread, and how patience and a second, differently attuned instrument may be what finally give it a name.
Scientists Spot Icy Object Beyond Pluto That Could Become the Solar System's Newest Dwarf Planet
A smaller, shinier object looks just like a larger, darker one.
Mark
Why does a number like 600 to 1,500 kilometres matter so much? That's a big spread.
Mimi
It's the whole question. The size decides how it ranks and feeds into whether it counts as a dwarf planet at all. Right now the spread comes from how it's being observed.
Luke
Right, and that spread is an estimate, not a measurement. Rubin sees reflected sunlight, so a small shiny object and a large dark one look the same.
Mark
So how do they break the tie?
Mimi
By looking at longer wavelengths with something like ALMA, which picks up the light the object gives off itself. That helps measure size.
Mark
And the roundness requirement?
Mimi
It needs enough mass for its own gravity to make it round. The object appears to have that, according to the researchers.
Luke
Note the word appears. The reporting says more observations are needed, so it's not confirmed. I'd also say the report doesn't tell us when those follow-ups will happen.
Mark
Who decides in the end?
Mimi
The International Astronomical Union, which has five recognised dwarf planets: Pluto, Eris, Haumea, Makemake and Ceres.
Luke
The source doesn't say how long a formal decision would take, or whether one has been requested. Only that it would be among the largest if confirmed.
Mark
Pluto's history hangs over this.
Mimi
It does. It was reclassified in 2006, and this object sits in the same cold region where Pluto lives.
El Pulso
- A newly found icy body beyond Pluto has stirred the astronomy world with the possibility of a new dwarf planet.
- Its size is stubbornly unclear, estimated anywhere from 600 to 1,500 kilometres because reflected light alone cannot tell a small bright body from a large dark one.
- Researchers are preparing to turn to ALMA in Chile, hunting for the heat-like light the object emits itself to pin down its true dimensions.
- The classification hangs in the balance, with confirmation of size and roundness still needed before 2026 ED138 can join the IAU's list of five dwarf planets.
High in the dry air of Chile, a telescope has glimpsed a faint icy world drifting in the deep cold past Pluto, a place where the solar system thins into scattered remnants of its own making. Designated 2026 ED138, the body may one day be counted among the dwarf planets, but for now it hangs in a kind of suspended question, its size still a matter of honest uncertainty. Its discovery reminds us how much of the outer sky remains unread, and how patience and a second, differently attuned instrument may be what finally give it a name.
A telescope on a mountaintop in central Chile has found an icy body circling in the dark far beyond Pluto. The Vera C. Rubin Observatory, perched on Cerro Pachón and run by the US National Science Foundation and Department of Energy, caught the object, now designated 2026 ED138. Astrophysicist Matt Holman of the Center for Astrophysics, Harvard & Smithsonian, who first spotted it, announced the find in Spokane, Washington, calling it a sign of the discoveries still waiting in the outer solar system.
The object orbits about 46 times farther from the sun than Earth, close to Pluto's distance, and may measure between 600 and 1,500 kilometres across. That wide range is the puzzle. Rubin sees only sunlight bounced off the body, and a small reflective rock can look identical to a large dark one. Confirming that 2026 ED138 is a dwarf planet means establishing its size and showing that its gravity has pulled it into a round shape, which its mass appears to allow.
The path forward runs through longer wavelengths. ALMA, the Atacama Large Millimeter/submillimeter Array, can detect the light the object gives off on its own, offering a clearer measure of its physical size. Those follow-up observations will decide whether this distant wanderer joins Pluto, Eris, Haumea, Makemake and Ceres on the list of recognised dwarf planets.
A telescope on a mountaintop in central Chile has turned up an icy body orbiting in the cold dark beyond Pluto, and it may end up on the short list of the solar system's dwarf planets. The object carries the designation 2026 ED138. It was found with the Vera C. Rubin Observatory, which sits on the summit of Cerro Pachón and is a joint initiative of the US National Science Foundation and the US Department of Energy.
The numbers so far are wide-ranging. Researchers estimate the object's diameter at somewhere between 370 and 930 miles, or 600 to 1,500 kilometres. It orbits about 46 times farther from the sun than Earth does. Pluto, by comparison, averages about 40 times Earth's distance. Both live in the same frigid region of the solar system, populated by assorted icy bodies.
The person who first spotted it is astrophysicist Matt Holman of the Center for Astrophysics, Harvard & Smithsonian. The discovery was announced at a scientific meeting in Spokane, Washington. Holman framed it as a sign of what is still to come, saying it shows that many exciting discoveries remain to be made with Rubin and other telescopes.
Whether 2026 ED138 earns the label is not settled. Further observations are needed. If it is confirmed, it would join five dwarf planets recognised by the International Astronomical Union, the global authority on classifying celestial bodies. Four of them, Pluto, Eris, Haumea and Makemake, orbit beyond Neptune, the outermost planet. The fifth, Ceres, sits in the main asteroid belt between Mars and Jupiter. On current data, 2026 ED138 would rank among the largest of them.
The classification itself has a history. Pluto was long counted as the ninth and outermost planet, until the IAU reclassified it as a dwarf planet in 2006 because it did not meet the organisation's formal definition of a planet. For dwarf planet status, an object needs enough mass for its own gravity to pull it into a round shape. 2026 ED138 appears to have enough mass to do that, but that, too, awaits more observation.
The central unknown is size. Holman said the main thing to do is establish the object's physical size. The difficulty is in how Rubin sees it: the telescope captures sunlight reflected off the object. A smaller, more reflective body would show the same amount of light as a larger, less reflective one, so brightness alone cannot separate the two cases. That helps explain the broad range in the diameter estimate.
The remedy, Holman said, is to look at longer wavelengths, where an observatory can detect light emitted by the object itself, which helps in measuring its size. He pointed to ALMA, the Atacama Large Millimeter/submillimeter Array, another powerful telescope based in Chile. The next step is follow-up observations of that kind, which would narrow the size estimate and bear on whether the object is formally recognised.
Citas Notables
The main thing we need to do is to establish the physical size of 2026 ED138.— Matt Holman, Center for Astrophysics, Harvard & Smithsonian
Many exciting discoveries remain to be made with the Rubin Observatory and other telescopes.— Matt Holman, astrophysicist
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