Astronomers have created the most detailed view yet of the Sculptor Galaxy, a nearby active spiral galaxy characterized by intense star formation and intricate structures. Using the European Southern Observatory’s Very Large Telescope in Chile, a team of researchers has assembled a massive map of the galaxy by collecting light across thousands of colors. The result is a detailed record of the gas, stars, and dust that make up the galaxy, and the insights are already changing our understanding of the universe.
The data comes from over 50 hours of observation using MUSE, the Multi Unit Spectroscopic Explorer, an instrument capable of capturing both images and spectra from each point in the sky. Instead of just photographing the galaxy, the scientists recorded its light in fine detail, breaking it down to learn what it’s made of, how it moves, and where stars are forming and dying.
“Galaxies are incredibly complex systems that we are still struggling to understand,” said Enrico Congiu, an astronomer at the European Southern Observatory who led the new study published in Astronomy & Astrophysics.
A Galaxy in a Sweet Spot
The Sculptor Galaxy is among the closest massive star-forming galaxies to our own Milky Way, lying just 11 million light-years away in the Southern Hemisphere’s constellation Sculptor. It’s visible even with binoculars. It spans roughly 90,000–100,000 light‑years across—comparable in scale to our Milky Way. Unlike the Milky Way, Sculptor is in a starburst phase, forming new stars every year.
But what makes it truly special, said Congiu, is its size and proximity. “It is close enough that we can resolve its internal structure and study its building blocks with incredible detail,” he said. “But at the same time, big enough that we can still see it as a whole system.”
This balance allowed Congiu’s team to create one of the most detailed and expansive spectroscopic maps ever assembled of a galaxy beyond our own. Over the course of 50 hours of observations and more than 100 separate exposures, they pieced together a 300-gigabyte mosaic that captures nearly 9 million spectra — each one a signature of the elements and activity in a tiny parcel of space.
Galaxies shine in a rainbow of emissions from gas, dust, and stars. Each of these building blocks emits light at specific wavelengths — fingerprints that reveal their age, motion, and chemical makeup. Most telescope images reduce this light to a few visible colors. MUSE records thousands.
The resulting image of Sculptor is a kaleidoscope of stellar birth and death. Bright pinks trace star-forming regions lit by glowing hydrogen. Wisps of blue highlight oxygen-rich shells around dying stars. A white funnel near the galaxy’s center marks a fountain of gas, blown outward by a central black hole.
“We can zoom in to study individual regions where stars form at nearly the scale of individual stars,” said Kathryn Kreckel of Heidelberg University, a co-author of the study. “But we can also zoom out to study the galaxy as a whole.”
A Galactic Census of the Dying Stars
One of the study’s major achievements is its catalog of more than 500 planetary nebulae. These glowing clouds of gas, named for their planet-like appearance in early telescopes, are not planets at all. They’re ephemeral sculptures of stardust expelled by dying stars, lasting tens of thousands of years.
In most galaxies beyond the Milky Way, astronomers are lucky to detect a few dozen of them. “Beyond our galactic neighbourhood, we usually deal with fewer than 100 detections per galaxy,” said Fabian Scheuermann, a doctoral student at Heidelberg University and co-author.
But in Sculptor, the team found hundreds, allowing them to build the most robust planetary nebula luminosity function (PNLF) ever made for this galaxy — a kind of brightness profile that can be used to estimate distance.
“Finding the planetary nebulae allows us to verify the distance to the galaxy — a critical piece of information on which the rest of the studies of the galaxy depend,” said Adam Leroy, an astronomer at Ohio State University and study co-author.
Rethinking the Distance to Sculptor
That measurement also led to a surprise. Based on the planetary nebulae, the researchers found that Sculptor may be farther away than previously thought: about 4.1 million parsecs (roughly 13.4 million light-years), which is 17% more distant than earlier estimates using red giant stars.
Why the discrepancy? Congiu and his team suggest the culprit is dust. Sculptor is viewed almost edge-on from Earth, and its dense spiral arms are laced with dark filaments of interstellar soot. This dust dims the light from stars and planetary nebulae alike, making them appear fainter — and therefore farther — than they really are.
They also found that the galaxy’s central region, which is particularly dusty, yielded even more inflated distance estimates. By isolating the outer disk, the team recovered a distance much closer to consensus values.
Ultimately, what sets this project apart is not just its depth, but its versatility. The map is a dataset that scientists around the world can mine for years.
It will help astronomers trace how gas flows through galaxies, how it cools and condenses to form new stars, and how supernovae and black holes blow material back out — a galactic cycle that fuels cosmic evolution.
“How such small processes can have such a big impact on a galaxy whose entire size is thousands of times bigger is still a mystery,” said Congiu.
The team’s work is part of a growing movement in astronomy to move beyond pretty pictures and build empirical, data-rich atlases of the cosmos. Similar efforts with the MUSE instrument are targeting other nearby galaxies, but few match the scale of the Sculptor mosaic.
For now, Sculptor shines as a cosmic laboratory and the data it’s offering us will shine as bright as its light.
