Webb Telescope Discovers Baby Planets at Various Development Stages

The James Webb Space Telescope has uncovered two large planets at distinct stages of their early development—one featuring a thick atmosphere filled with dusty clouds and the other surrounded by a disk of material—orbiting a youthful sun-like star. This finding sheds light on the intricate process of planetary system formation.

These two gas giants, which are both more massive than Jupiter, were directly imaged by Webb in a planetary system located about 310 light years away from Earth in the Milky Way, in the direction of the constellation Musca. A light year is the distance light travels in a year, equivalent to about 5.9 trillion miles (9.5 trillion kilometers).

Since the 1990s, astronomers have identified over 5,900 exoplanets beyond our solar system, but fewer than 2% have been imaged directly, making it unusual to observe planets in their formative stages.

The development of a planetary system starts with a vast cloud of gas and dust (known as a molecular cloud) that collapses under its own gravity, forming a central star. The leftover material orbiting the star creates a protoplanetary disk from which planets are formed.

This particular system, observed by Webb, is at a very early stage of development. The star, designated YSES-1, has a mass comparable to that of the sun. The two planets revolve around the star at considerable distances, each likely taking thousands of years to complete one orbit.

While the sun is approximately 4.5 billion years old, YSES-1 is merely about 16 million years old, akin to a newborn star. Researchers were intrigued to observe that the two young planets displayed differing stages of development.

The innermost planet has a mass roughly 14 times that of Jupiter, orbiting its star at a distance 160 times that of Earth from the sun—more than five times farther than Neptune, our solar system’s farthest planet. This planet is surrounded by a disk of fine dust, a sign that it may still be in an early stage of formation or possibly a result of recent collisions or the emergence of a moon. Webb’s observations detected water and carbon monoxide in its atmosphere.

The outer planet is around six times the mass of Jupiter and orbits at a distance 320 times that of Earth from the sun. Its atmosphere is rich in silicate clouds, which contrasts sharply with the gas giants in our own solar system. Webb also identified methane, water, carbon monoxide, and carbon dioxide in this planet’s atmosphere, but it lacks any material disk.

The unusual characteristics of these two planets in the same system underscore the complexities of planet formation and highlight how much remains unknown about how various planetary systems—including our own—develop, remarked astrophysicist Kielan Hoch from the Space Telescope Science Institute in Baltimore, who led the study recently published in the journal Nature.

“Theoretically, the planets should be forming around the same time since planet formation occurs relatively quickly, within about a million years,” Hoch stated.

One of the significant mysteries is the exact location where these planets formed, as their distance from the host star is greater than what would typically be expected from a protoplanetary disk.

“Additionally, the reasons behind one planet retaining material while the other boasts distinct silicate clouds are intriguing. Shouldn’t all giant planets formed in similar circumstances exhibit the same traits? These are questions we’ve explored to better understand the formation of our solar system,” Hoch added.

Since its launch in 2022, the James Webb Space Telescope has made tremendous contributions to our understanding of the early universe, particularly in the study of exoplanets, thanks to its observations in the near- and mid-infrared spectrum.

“Webb is uncovering a wealth of atmospheric physics and chemistry in exoplanets that were previously unknown, and it’s currently challenging the atmospheric models we used before Webb,” Hoch remarked.