Astronomers Confirm Youngest Known Planet, Still Forming in Its Dusty Cradle

Astronomers have confirmed a planet less than a million years old — the youngest known to science — still moving through the disk of dust and gas from which it formed. Named Elias 2-24 b, the planet was identified using data from NASA-funded archives, the US space agency said.

The planet orbits a star called Elias 2-24, about 450 light-years from Earth, and has a mass roughly similar to Jupiter's. One light-year is the distance light travels in a year, about 9.5 trillion kilometres.

The findings were published on Wednesday in The Astrophysical Journal Letters. The team, led by Andrea Bernardi, a doctoral candidate at the Universidad Diego Portales in Chile, studied archival observations of seven stars. The observations were made using a coronagraph at the W M Keck Observatory in Hawaii, which partners with NASA under a cooperative agreement.

A coronagraph blocks the light of a star so that astronomers can search for fainter planets within the dusty disks around it. These disks contain dust, gas, ice and rock, and show gaps and other structures that can indicate planets are forming.

Bernardi said planets should be found within those gaps because they create them, adding that this is exactly where the team found Elias 2-24 b.

Lucas Cieza, a professor at the Instituto de Estudios Astrofísicos in Chile and a co-author of the study, said existing planet-formation models already struggled to explain the previously youngest known planets, all of which were more than five million years old. He said Elias 2-24 b shows that important processes are still missing from even the best of those models.

Stars form inside swirling clouds of gas and dust. Planets develop from leftover material that gradually clumps together and carves a path around the star. Studying newborn planets is difficult, however, because thick dust can hide them.

Most confirmed exoplanets — planets outside our solar system — have been detected through transits, when a planet passes in front of its star and briefly reduces the light reaching Earth. Transits are hard to detect when planets are buried in dust or orbit far from their stars. As a result, most of the roughly 6,000 confirmed exoplanets are billions of years old and orbit close to their stars.

The work carries wider significance. Understanding how planets form is central to understanding how Earth and the solar system came to be. The disks around young stars are the same kind of environment in which the Sun and its planets are thought to have formed about 4.6 billion years ago.

Scientists use theories, simulations and observations of young stars with disks to understand how planets form. Finding more young planets such as Elias 2-24 b could help astronomers improve these models.

Cieza said the galaxy continuously produces new stars and planets, meaning objects exist at every stage of evolution. He added, however, that there is a large gap in what most telescopes can detect, leaving scientists mostly unable to observe these infant planets.

The discovery rests on archived data rather than new observations, a reminder that existing telescope records can still yield significant findings. Independent confirmation and further study will help establish how Elias 2-24 b fits with other known planetary systems.