NASA’s James Webb Space Telescope has resolved a longstanding mystery by confirming a controversial discovery made by the Hubble Space Telescope over 20 years ago.

Figure 1. NASA’s Webb Uncovers Extended Lifetimes of Planet-Forming Disks in the Early Universe.

In 2003, Hubble detected evidence of a massive planet orbiting an ancient star, nearly as old as the universe itself. These stars contain minimal amounts of heavy elements—the fundamental building blocks of planets. This suggested that planet formation occurred very early in the universe’s history, with planets growing inside primordial disks to enormous sizes, even larger than Jupiter. But how was this possible? Figure 1 shows NASA’s Webb Uncovers Extended Lifetimes of Planet-Forming Disks in the Early Universe.

To investigate, researchers used Webb to study stars in a nearby galaxy that, like the early universe, has very few heavy elements. Webb revealed that some stars in this environment still host planet-forming disks, and remarkably, these disks persist far longer than those around young stars in the Milky Way.

“With Webb, we now have strong evidence supporting what Hubble observed, forcing us to rethink planet formation models and the evolution of the early universe,” said Guido De Marchi, the study’s leader from the European Space Research and Technology Centre in Noordwijk, Netherlands.

A Unique Early Universe Environment

In the early universe, stars primarily formed from hydrogen and helium, with heavier elements like carbon and iron appearing later after supernova explosions.

“Current models suggest that in such metal-poor environments, planet-forming disks should have very short lifetimes—too short for planets to grow,” explained Elena Sabi, co-investigator and chief scientist at the National Science Foundation’s NOIRLab in Tucson. “But Hubble spotted those planets. What if our models are wrong, and disks actually last longer?”

To test this, scientists directed Webb’s attention to the Small Magellanic Cloud, a dwarf galaxy close to the Milky Way. Within it lies NGC 346, a massive star-forming cluster with a low abundance of heavy elements, similar to conditions in the early universe.

Hubble’s mid-2000s observations of NGC 346 identified many stars between 20 and 30 million years old that still appeared to have planet-forming disks. This defied the expectation that such disks would dissipate within 2–3 million years.

“The Hubble findings were controversial because they contradicted both observations in our galaxy and existing models,” said De Marchi. “However, without spectra, we couldn’t confirm whether these disks were genuine or just artifacts.

Webb’s advanced sensitivity and resolution provided the first-ever spectra of Sun-like stars and their surroundings in a nearby galaxy.

“We confirmed that these stars are indeed surrounded by disks and are actively accreting material, even at the relatively old age of 20 to 30 million years,” De Marchi stated. “This means planets have far more time to form and grow than we previously thought.”

Rethinking Planet Formation

The discovery challenges prior theories suggesting that stars with low heavy-element content rapidly disperse their disks via radiation pressure. Without these long-lived disks, planets wouldn’t have enough time to form.

Researchers proposed two potential explanations for the persistence of planet-forming disks in such environments:

1. Reduced Radiation Pressure: For radiation pressure to effectively disperse a disk, heavier elements must exist within the gas. In NGC 346, where heavy elements are only 10% as abundant as those in the Sun, the dispersal process may take longer.
2. Larger Gas Clouds: Stars forming in metal-poor environments may originate from larger gas clouds, leading to more massive disks. These disks contain more material and require more time to disperse, even with the same radiation pressure at play.

“With more mass surrounding these stars, accretion continues for much longer,” said Sabbi. “The disks last about ten times longer than expected, which has profound implications for how planets form and the types of planetary systems that can emerge in different environments. It’s incredibly exciting!”The study’s findings were published in the December 16 issue of The Astrophysical Journal.

Webb and Hubble’s Legacy

The James Webb Space Telescope is the leading observatory for space science, exploring mysteries of our solar system, distant exoplanets, and the origins of the universe. Webb is a collaborative effort led by NASA, alongside ESA (European Space Agency) and CSA (Canadian Space Agency).

Meanwhile, the Hubble Space Telescope continues to redefine our understanding of the cosmos after more than 30 years of groundbreaking discoveries. Operated jointly by NASA and ESA, Hubble’s mission is managed by NASA’s Goddard Space Flight Center, with support from Lockheed Martin Space and science operations conducted by the Space Telescope Science Institute in Baltimore.

Source: EureAlert

Cite this article:

Priyadharshini S (2024), NASA’s Webb Reveals Planet-Forming Disks Lasted Longer in The Early Universe,Anathemas pp. 145