James Webb Telescope Resolves 20-Year Hubble Mystery, Sheds Light on the Universe’s Oldest Planets
The James Webb Space Telescope (JWST) has unraveled a 20-year-old mystery about the formation of massive planets around ancient stars.
In the early 2000s, the Hubble Space Telescope discovered the universe’s oldest known planet — a gas giant 2.5 times the size of Jupiter — that formed 13 billion years ago, just a billion years after the Big Bang. Similar discoveries of ancient planets soon followed, perplexing astronomers. Stars in the early universe, primarily composed of light elements like hydrogen and helium, were thought to lack the heavy elements, such as carbon and iron, necessary to form planets.
Researchers believed radiation from these stars would quickly disperse the surrounding dust and gas, preventing the formation of long-lasting planetary disks. Heavy elements, introduced only later by supernovae, were assumed to be critical for planet formation.
However, new findings from the JWST challenge this assumption. Detailed observations of a modern-day analog to these ancient stars reveal that long-lasting planetary disks are indeed possible in low-metallicity environments. The research, published on December 16 in The Astrophysical Journal, confirms that ancient planetary systems could have formed under these conditions.
“We see that these stars are indeed surrounded by disks and are still in the process of gobbling material, even at the relatively old age of 20 [million] or 30 million years,” said Guido De Marchi, lead author of the study and astronomer at the European Space Research and Technology Centre in the Netherlands. “This also implies that planets have more time to form and grow around these stars than in nearby star-forming regions in our own galaxy.”
James Webb’s Key Observations
The JWST studied stars within NGC 346, a star-forming cluster in the Small Magellanic Cloud, located 199,000 light-years from Earth. Conditions in this cluster mirror the early universe, with stars composed mostly of light elements and sparse heavy metals. By analyzing the light spectra from these stars, researchers found evidence of long-lasting planetary disks around them.
The study proposes two explanations for this phenomenon. First, stars made primarily of light elements may produce less radiation capable of dispersing the surrounding disks, allowing them to persist for millions of years. Alternatively, these stars could form from massive clouds of dust and gas, leaving behind substantial disks that take much longer to dissipate, even in the presence of radiation.
“This has implications for how planets form and the types of planetary systems that can emerge in different environments,” said study co-author Elena Sabbi, chief scientist at the Gemini Observatory. “This is so exciting.”
The JWST’s groundbreaking observations provide new insights into the conditions under which planets can form, reshaping our understanding of planetary system evolution in the early universe.
