Astronomers have unveiled a captivating view into the birth of solar systems similar to our own, with the discovery of planet-forming ‘pebbles’ around two young stars. These findings, presented at the Royal Astronomical Society’s National Astronomy Meeting 2025 in Durham, mark a significant advancement in understanding how planets, including those in our solar system, come into existence.
The discovery was made around the stars DG Tau and HL Tau, located approximately 450 light-years from Earth. Researchers observed protoplanetary discs extending to at least Neptune-like orbits around these stars. These discs are believed to contain the building blocks of planets, gradually clumping together in a process akin to the formation of Jupiter 4.5 billion years ago, followed by the other planets in our solar system.
The Significance of Protoplanetary Discs
Protoplanetary discs, the cosmic nurseries where planets are born, have long been a subject of fascination for astronomers. The recent observations provide crucial insights into these discs, revealing large reservoirs of planet-forming pebbles. According to Dr. Katie Hesterly of the SKA Observatory, “These observations show that discs like DG Tau and HL Tau already contain large reservoirs of planet-forming pebbles out to at least Neptune-like orbits. This is potentially enough to build planetary systems larger than our own solar system.”
The research is part of the PEBBLeS project (Planet Earth Building-Blocks — a Legacy eMERLIN Survey), led by Professor Jane Greaves of Cardiff University. The project aims to uncover how often and where planets form around stars destined to become future suns like ours.
Innovative Techniques and Tools
The PEBBLeS project utilizes e-MERLIN, an interferometer array of seven radio telescopes spanning 217 km across the UK. This network, connected by a superfast optical fibre to Jodrell Bank Observatory in Cheshire, is currently the only radio telescope capable of studying protoplanetary discs with the necessary resolution and sensitivity.
Professor Greaves explained, “Through these observations, we’re now able to investigate where solid material gathers in these discs, providing insight into one of the earliest stages of planet formation.” Since the 1990s, astronomers have identified disks of gas and dust and nearly 2,000 fully-formed planets, but detecting intermediate stages has proven challenging.
The Role of e-MERLIN
Dr. Anita Richards from the Jodrell Bank Centre for Astrophysics highlighted the importance of e-MERLIN in this research. “Decades ago, young stars were found to be surrounded by orbiting discs of gas and tiny grains like dust or sand,” she said. “Enough grains to make Jupiter could be spread over roughly the same area as the entire orbit of Jupiter, making this easy to detect with optical and infra-red telescopes, or the ALMA submillimeter radio interferometer.”
“But as the grains clump together to make planets, the surface area of a given mass gets smaller and harder to see,” Dr. Richards added.
e-MERLIN’s ability to observe at around 4 cm wavelength makes it ideal for detecting centimetre-sized pebbles, which emit best at wavelengths similar to their size. Recent images of DG Tau’s disc reveal that such pebbles have already formed out to Neptune-like orbits, with similar findings around HL Tau.
Looking Ahead: The Future of Planetary Observation
These discoveries offer a glimpse into what future telescopes, like the Square Kilometre Array (SKA) in South Africa and Australia, will uncover. With its enhanced sensitivity and scale, the SKA will enable astronomers to study protoplanetary discs across the galaxy in unprecedented detail.
“e-MERLIN is showing what’s possible, and the SKA telescope will take it further,” said Dr. Hesterly. “When science verification with the SKA-Mid telescope begins in 2031, we’ll be ready to study hundreds of planetary systems to help understand how planets are formed.”
The ongoing advancements in astronomical technology and research methodologies continue to push the boundaries of our understanding of the universe. As scientists prepare for the next decade of exploration, the mysteries of planet formation are slowly being unveiled, offering new insights into the origins of our own solar system and beyond.
