Queen’s Belfast team finds two elusive asteroids trailing Neptune

A team led by Queen’s University Belfast has discovered two asteroids in long-lived orbits trailing Neptune, along with a further candidate. The researchers used early observations from the Vera C. Rubin Observatory in Chile to track down the faint, distant objects.

Dr Meg Schwamb, an astronomer and lecturer at Queen’s Astrophysics Research Center, led the international collaboration. Its findings have been published in The Astrophysical Journal Letters.

The objects belong to Neptune’s trailing Trojan population: bodies that share the planet’s journey around the Sun while following behind it. Schwamb said the discoveries doubled the known number of objects in this population with long-lived orbits.

Why they were hard to find

For the past 10 years, these faint objects have appeared against the bright, crowded centre of the Milky Way when viewed from Earth. That backdrop made them difficult for astronomers to pick out.

The trailing group has begun moving away from that region of the sky. Combined with Rubin’s ability to detect faint objects across a wide area, that shift allowed the team to identify the asteroids in data from early test observations in 2025.

Images taken through different filters also showed that the objects ahead of Neptune and those behind it have similar surfaces.

Rubin began operations in June 2025. Over the next nine years, its survey is expected to identify tens to hundreds of Neptune Trojans across the leading and trailing groups, as well as tens of thousands of icy bodies beyond Neptune and in the Kuiper Belt.