How do planets like Earth and Jupiter come into existence?
Astronomers are beginning to answer that question thanks to new observations from the European Space Agency’s Gaia space telescope, which is offering an unprecedented look at some of the youngest planetary systems in our galaxy.
Gaia has been studying stars across the Milky Way with extraordinary precision, measuring their positions and motions over time.
In a recent study, astronomers used Gaia’s data to search for signs of hidden companions—such as planets—around stars that are only about a million years old.
These stars have only just formed from huge clouds of gas and dust, making them cosmic infants.
When a cloud of gas collapses under gravity, it begins to spin and flatten into a disk.
The dense, hot center becomes a star, while the surrounding material forms a swirling structure known as a protoplanetary disk.
Over time, dust and gas in these disks clump together and grow into planets. The problem is that these disks are thick and dusty, which makes it extremely difficult to see young planets directly.
That’s where Gaia comes in. Instead of trying to photograph planets, Gaia looks for tiny movements in stars themselves.
As a planet or other object orbits a star, its gravity causes the star to wobble slightly. Gaia can detect these subtle motions with remarkable accuracy.
In a sample of 98 young star systems, Gaia detected unusual motions in 31 of them. For seven systems, the data suggest the presence of objects with masses similar to planets.
In eight others, the signals point to brown dwarfs—objects that are too large to be planets but too small to shine as full stars. The remaining systems likely contain additional stars.
To help visualize these findings, astronomers compared the young systems to what our own solar system might have looked like at the same age.
In this early stage, the Sun would have been surrounded by a disk of material, with Jupiter already forming within it. Gaia’s measurements suggest that some of the newly detected companions orbit their stars at distances similar to Jupiter’s orbit around the Sun.
This is the first time Gaia’s technique has been used to identify planet-sized companions around stars that are still forming. Previous methods worked mainly for older, more settled stars. Because Gaia surveys the entire sky, it allows scientists to study many young systems at once, rather than focusing on just a few targets.
The discoveries are opening a new chapter in the study of how stars and planets grow together. The candidate planets identified by Gaia can now be studied in more detail by powerful telescopes such as the James Webb Space Telescope, which can peer into the dusty inner regions of these systems.
With Gaia’s next major data release on the way, astronomers expect many more hidden worlds to emerge, bringing us closer to understanding how planetary systems—including our own—are born.
