How is it possible to know what our Milky Way Galaxy looks like, when we’re inside it?
How could we ever hope to see it from the perspective of a distant observer, when we’re just a tiny speck orbiting a single star in a galaxy of up to 400 billion stars?
The European Space Agency’s Gaia mission has gone a long way to answering these questions, having created the most accurate 3D map of the Milky Way ever made.
Now a new 3D animation using Gaia data enables the viewer to fly through a star-forming region of the Milky Way, and to see what our Galaxy would look like from ‘above’.
How to map the Milky Way
The Gaia mission launched in December 2013 and gathered data on over a billion stars throughout its mission, which ended in January 2025.
This new 3D animated map of a star-forming region in the Milky Way was created using Gaia’s measurements of stellar positions and the so-called ‘extinction’ of stars.
That refers to Gaia’s view of starlight blocked by thick cosmic dust.
Scientists use this information to create 3D maps showing where dust is distributed in the Milky Way, and those maps reveal the location of ionised hydrogen gas, which is a telltale sign that new stars are being born.
The 3D map of a star-forming region of our Galaxy is based on Gaia’s observations of 44 million ‘ordinary’ stars and 87 ‘O-type’ stars
It stretches out to a distance of 4,000 lightyears from our Solar System, with our Sun in the centre.
The 87 O-types are a rare type of star. They’re young, massive, scorchingly hot and very bright.
They glow in ultraviolet light, ionising the hydrogen gas surrounding them and thereby revealing themselves to astronomers in the process.
These regions are well-known to astronomers, but the Gaia data shows what they look like in 3D, and how they would appear from an outside perspective.
Milky Way from above
Gaia’s 3D maps reveal the motions and positions of millions of nearby stars, enabling scientists to map the location of stars and interstellar material near the Sun.
In this way, they can produce illustrations accurately showing what our Milky Way would look like from afar.
It’s effectively impossible for a human-made spacecraft to travel the distance to show us what the Milky Way really looks, so this is the best way of seeing it for ourselves.
“Gaia provides the first accurate view of what our section of the Milky Way would look like from above,” says Lewis McCallum, astronomer at the University of St Andrews, UK, first author of two scientific papers explaining the 3D model.
“There has never been a model of the distribution of the ionised gas in the local Milky Way that matches other telescope’s observations of the sky so well. That’s why we are confident that our top-down view and fly-through movies are a good approximation of what these clouds would look like in 3D.”
The map includes 3D views of the Gum Nebula, the North America Nebula, the California Nebula and the Orion-Eridanus superbubble.
Investigating the interstellar
The 3D map is more than just an interesting view of our Milky Way; it’s giving astronomers the chance to learn more about giant O-type stars and how they energise gas in our Galaxy.
Lewis and the team say they’ve already noticed some of the clouds in star-forming regions have broken open, allowing gas and dust to stream into a huge cavity.
“This map nicely shows how radiation of massive stars ionises the surrounding interstellar medium and how dust and gas interact with this radiation,” says Sasha Zeegers, ESA Research Fellow.
“The 3D model provides a detailed look at the processes that shape our local galactic environment and helps astronomers understand interactions between the warm and cold components of the local Universe.”
What’s more, there are already plans to extend the map to cover an even larger region of our Galaxy.
“It required huge computational power to generate the map out to ‘just’ 4000 lightyears from the Sun in high resolution,” says Lewis.
“We hope that the map can be expanded further out once Gaia has released its new set of data.”
“Gaia’s distance measurements of the nearby hot stars, and the 3D maps of dust – obtained from measuring the extinction and positions of millions of ordinary stars using Gaia data – are both crucial ingredients of this new map,” says Johannes Sahlmann, ESA’s Gaia Project Scientist.
“Gaia’s fourth data release will contain data of even better quality and quantity, making it possible to further advance our knowledge of star-forming regions.”