In March 2025, Australia's new SKA-Low telescope photographed 85 galaxies using just 1,024 of its planned 131,072 antennas — less than one percent of its full power, and the image was already beyond what scientists hoped for

In March 2025, Australia’s new SKA-Low telescope took a picture of the sky dotted with 85 galaxies. It did so using just 1,024 of the 131,072 antennas it will eventually have, less than one per cent of the finished instrument. And even at that tiny fraction of its planned power, the image came out better than the scientists behind it had hoped.

That combination, a scrap of the telescope producing a clean, useful picture, is exactly why the result mattered. It was less a discovery about the universe than a sign of what this machine will be able to do once it is whole.

A telescope made of thousands of antennas

SKA-Low is not a single dish. It is a vast array of simple antennas, each a spindly metal structure a bit like a Christmas tree, spread across the remote Western Australian outback at a site known as Inyarrimanha Ilgari Bundara, on Wajarri Yamaji Country. Their signals are combined electronically so that the whole field of antennas behaves as one enormous radio telescope tuned to low-frequency radio waves.

It is one half of the Square Kilometre Array Observatory, an international effort building the largest radio telescope facility ever attempted. The low-frequency half sits in Australia, while a sister array of dish antennas, SKA-Mid, is being built in South Africa.

The first image

The March 2025 picture was made with 1,024 antennas grouped into four stations, an early sliver of an array that will eventually run to hundreds of stations. It covered a patch of sky about 25 square degrees across, roughly the area a hundred full Moons would cover, and in it sat about 85 well-known galaxies, each one a distant system harbouring a supermassive black hole that shines brightly at radio wavelengths.

Eighty-five galaxies is not, on its own, a headline number. The significance is the ratio behind it. This was under one per cent of the eventual telescope, and it already delivered a crisp, scientifically usable image. The team said plainly that the quality exceeded what they had expected from such an early version of the instrument.

Why less than one per cent already impresses

Building a telescope from scratch out of tens of thousands of separate antennas is as much a software and engineering problem as an astronomical one. Every antenna’s signal has to be captured, timed and combined with all the others precisely enough that they add up into a single coherent view of the sky. Getting that to work at all, and getting it to work well, is the hard part.

The first image is proof that the design does work. A handful of stations, combined correctly, produced a clean result, which means the same approach should scale. As more antennas and stations are switched on, the telescope’s sensitivity and sharpness will climb steeply, and the same patch of sky will reveal far more than 85 galaxies. By the time roughly 68 stations are operating, expected around the end of 2026, that same field is projected to reveal something on the order of hundreds of thousands of galaxies.

What SKA-Low is built to do

The reason for building a telescope this large at low frequencies is that those wavelengths open a window onto the early universe that is very hard to see any other way. SKA-Low is designed, among other goals, to probe the cosmic dawn and the epoch of reionisation, the era when the first stars and galaxies switched on and burned away the fog of neutral hydrogen that filled the young cosmos.

It is worth being clear that the first image is not that science yet. Mapping bright radio galaxies is a demonstration of capability, a commissioning step. The faint, subtle signal from the early universe will demand the far larger, fully built array and years of careful observation. The March image is the machine clearing its throat, not yet singing.

The scale of the finished array

When complete, SKA-Low will comprise 131,072 antennas arranged in hundreds of stations scattered across many kilometres of the Australian desert. Together with its South African counterpart, it will form an observatory of a scale radio astronomy has never had before, able to survey the sky faster and see fainter objects than any predecessor.

Construction is a multi-year undertaking stretching across the rest of the decade, with the array growing station by station and its capabilities rising as it goes. Each expansion is both a construction milestone and a scientific upgrade.

What to watch

The near-term thing to watch is simply the array getting bigger, and the images getting deeper and sharper as more stations come online through 2026 and beyond. Each step will push the number of detectable galaxies upward and bring the instrument closer to the sensitivity its headline science requires.

The longer game is the cosmic-dawn signal, the faint whisper from the universe’s first light that SKA-Low was largely built to catch. For now, a picture assembled from less than one per cent of the telescope has already outrun expectations, which is a promising way for the largest radio telescope ever built to begin.