Cambridge, UK – July 20, 2025 – In a monumental achievement for astrophysics, an international team of astronomers, led by researchers at the University of Cambridge, has effectively “caught in the act” a giant exoplanet in the early stages of formation, hidden within the thick disk of gas and dust surrounding a young star. The groundbreaking discovery, initially reported on July 14th and gaining widespread attention this week, offers unprecedented insights into how planets are born and could revolutionize our understanding of solar system evolution.

The nascent giant, estimated to be between three and ten times the mass of Jupiter, was found orbiting the star MP Mus, which was previously believed to be a solitary star with no signs of orbiting planets or distinct features in its surrounding protoplanetary disk.

Hiding in Plain Sight: A Combination of Observational Prowess

For years, observations of MP Mus’s protoplanetary disk – the pancake-like cloud of gas, dust, and ice where planets begin to form – showed it to be surprisingly flat and featureless, devoid of the telltale gaps or spiral arms often associated with nascent planets.

However, the international team combined precise star movement data from the European Space Agency’s (ESA) Gaia mission with deeper observations from the Atacama Large Millimeter/submillimeter Array (ALMA). This innovative dual approach proved crucial. Gaia’s astrometry, which meticulously measures the positions and motions of stars, revealed a subtle “wobble” in MP Mus – a gravitational tug that hinted at an unseen orbiting companion.

“Our earlier observations showed a boring, flat disc,” said Dr. Anna Ribas, a lead researcher on the project from the University of Cambridge. “But when we paired the Gaia data with longer ALMA wavelengths, we could probe deeper into the disc.”

The longer ALMA wavelengths allowed the astronomers to pierce through the “stellar fog,” revealing a cavity in the disk close to the young star and two further “holes” or gaps further out, which were entirely absent in previous, shallower observations. “Our modeling work showed that if you put a giant planet inside the newfound cavity, you can also explain the Gaia signal,” Ribas added.

This marks the first time that an exoplanet embedded in a protoplanetary disk has been indirectly discovered by combining precise stellar movement data from Gaia with deep observations of the disk from ALMA.

A Glimpse into Our Own Solar System’s Past

The process of planet formation, known as core accretion, involves particles within the protoplanetary disk gradually sticking together via gravity, forming larger bodies that eventually grow into planets. As these young planets accumulate material, their gravitational pull carves out channels or “grooves” in the disk, similar to a vinyl record. The newly observed features in MP Mus’s disk match theoretical predictions for how a forming giant planet should shape its surrounding environment.

“This is incredibly exciting because it provides us with a rare, direct glimpse into the very earliest stages of planet formation,” commented another team member. “It’s like looking at a picture of our own solar system when it was just beginning to coalesce.”

The discovery suggests that many more “hidden planets” might exist in other protoplanetary disks, camouflaged by the dense gas and dust, just waiting for advanced observational techniques to reveal them. By studying how planets form in these distant stellar nurseries, astronomers can gain invaluable insights into the chaotic and dynamic processes that shaped our own solar system billions of years ago. The research is expected to pave the way for future observations with next-generation telescopes, potentially allowing for direct imaging of these nascent giants.