A new 3D map allows, for the first time, to 'fly' around, through, and above the clouds of dust and gas where stars are born.

In an unprecedented advance in our understanding of our own galaxy, an international team of scientists has used data from the European Gaia space telescope to create the most accurate three-dimensional map yet of star-forming regions in our region of the Milky Way—vast clouds of dust and gas that obscure the "births" that continually occur within them. The work has just been published in two separate articles in the Monthly Notices of the Royal Astronomical Society ( here and here ).

Until now, the task of mapping and studying these 'stellar hotbeds' was akin to trying to see the shape of a city by looking through a dense fog. And while astronomers have been able to get an idea of ​​what these nebulae look like from our perspective, they completely lacked the third dimension: depth. That is, they didn't know how far away they were, how far they extended, or how they were distributed in space—information without which it's impossible to fully understand the interactions between the stars that are born and their surrounding environment.

But that's what Gaia is for , a mission of the European Space Agency (ESA) that, between December 2013 and March 2025, has been collecting data on the position, motion and speed of more than a billion stars, with the aim of creating a detailed 3D map of our region of the galaxy.

But that's not all. Although Gaia can't directly "see" the clouds where new stars are born, it can accurately measure so-called stellar "extinction," a phenomenon that occurs when a star's light is dimmed or "quenched" by the interstellar material that stands in its way. And that's precisely what the researchers have done this time.

If we drive at night on a foggy road, the city lights in the distance will appear dimmer and sometimes even reddish, as fog scatters blue light from headlights more efficiently than red light. A similar thing happens in space: cosmic dust blocks blue light more than red light, making stars appear redder than they really are. By measuring this attenuation of light, it's possible to determine with relative accuracy how much dust there is in a given direction and distance. And that's exactly what Gaia can do, and with unprecedented precision.

Specifically, the new 3D map of star-forming regions near us was constructed from observations of 44 million "ordinary" stars and 87 O-type stars, which are the true "stars" of the story. These are extremely rare stars in the Universe, young, massive, and so incredibly hot and luminous that they shine brightly in the ultraviolet part of the electromagnetic spectrum. Their light is so energetic that it is capable of ionizing the hydrogen gas surrounding them, that is, stripping electrons from atoms and turning the neutral gas into a soup of charged particles.

This emission of ionized hydrogen is, in itself, an unmistakable sign that a veritable frenzy of star birth is taking place in this region. While other telescopes have allowed us to obtain magnificent two-dimensional images of these nebulae, such as the Barnard's Loop Nebula or the Orion Nebula, we have never before had such a detailed three-dimensional view. The new map extends up to 4,000 light-years from the Sun, covering a significant portion of our galactic neighborhood.

"Gaia," explains Lewis McCallum, an astronomer at the University of St Andrews in the United Kingdom and lead author of both papers, "gives us the first accurate view of what our section of the Milky Way would look like from above."

Thanks to the three-dimensional mapping and stellar motion data provided by Gaia, scientists have been able to create an almost cinematic representation of what these regions would look like from an external perspective—something we could only dream of until now. The model also perfectly matches observations from other telescopes, increasing confidence in its accuracy.

The result is a spectacular map that includes three-dimensional views of iconic nebulae such as the Gum Nebula (a supernova remnant about 1,300 light-years from Earth), the North America Nebula (NGC 7000, 1,800 light-years from Earth and so named because its profile resembles that of that continent), the California Nebula (NGC 1499, home to the enormous 'O'-type star Xi Persei) and the gigantic Orion-Eridanus superbubble.

Now, for the first time, astronomers can fly around, through, and above any of these regions, allowing them to study their structure, their streams of gas and dust, and their relationship to the stars being born within them.

But perhaps the most intriguing finding of this new map is the confirmation of the existence of a gigantic "cavity," a kind of "bubble" of empty space (which can be seen at second 4 of the attached video) and which, according to ESA researcher Sasha Zeegers, could have formed as radiation from very massive stars ionizes the interstellar medium. "The 3D model," says the researcher, "provides a detailed view of the processes that shape our local galactic environment and helps astronomers understand the interactions between the warm and cold components of the local Universe."

But the creation of this map is, according to the researchers, just the beginning. Generating such a high-resolution model out to a distance of 4,000 light-years has already required immense computational power, and scientists hope that future versions of the map, which will include new Gaia data, can extend even further into the Milky Way. “Gaia,” says Johannes Sahlmann, ESA’s Gaia project scientist, “has revolutionized our view of the solar neighborhood, allowing scientists to map stars and interstellar material near the Sun in a way that was previously impossible.”

In fact, Gaia's fourth release of data (Gaia Release 4), scheduled for December 2026, promises even greater quality and quantity, allowing astronomers to further advance their understanding of the regions where stars are born. Later, in 2030, Gaia Release 5 will also be published with the remaining data from the probe that remains to be analyzed. With each new data release, therefore, despite being offline for months, Gaia will continue to provide a detailed and unprecedented view of our region of the Milky Way, helping us unravel the processes that have shaped it over billions of years. In essence, this new 3D map is not just an atlas, but a time machine that allows us to peer into the past and understand the processes that continue to drive the birth and death of stars.