For the first time, a phenomenon that astronomers had long hoped to capture directly has been captured by the Near Infrared Camera (NIRCam) on NASA’s James Webb Space Telescope. In this stunning image of the Serpens Nebula, the discovery is located in the northern part (seen in the upper left corner) of this young, nearby star-forming region.
Astronomers have discovered an intriguing group of protostellar outflows, formed when jets of gas ejected from newborn stars collide with nearby gas and dust at high speeds. Usually these objects have a different orientation within a region. Here, however, they are inclined in the same direction, to the same degree, like snow falling in a storm.
The discovery of these aligned objects, made possible by Webb’s exceptional spatial resolution and sensitivity at near-infrared wavelengths, provides insights into the fundamentals of how stars are born.
“Astronomers have long assumed that when clouds break up to form stars, the stars will rotate in the same direction,” said lead researcher Klaus Pontoppidan of NASA’s Jet Propulsion Laboratory in Pasadena, California. “However, this has not been seen so directly before. These aligned, elongated structures are a historical record of the basic way stars are born.
So how does the alignment of stellar jets relate to the rotation of the star? As an interstellar gas cloud slams into itself to form a star, it spins faster. The only way for the gas to continue moving inward is for some of the spin (known as angular momentum) to be removed. A disk of material forms around the young star to transport material downward, like an eddy around a drain. Rotating magnetic fields in the inner disk shoot some of the material into twin jets that are shot outward in opposite directions perpendicular to the disk of material.
In Webb’s image, these jets are indicated by bright clumps that appear red, which are shock waves from the jet hitting the surrounding gas and dust. Here, the red color represents the presence of molecular hydrogen and carbon monoxide.
“This region of the Serpens Nebula — Serpens North — is only clearly visible with Webb,” said lead author Joel Green of the Space Telescope Science Institute in Baltimore. “We are now able to capture these extremely young stars and their outflows, some of which previously appeared simply as blobs or were completely invisible at optical wavelengths due to the dense dust surrounding them.”
Astronomers say there are several forces that can potentially change the direction of the outflow during this period of a young star’s life. One way is when binary stars orbit each other and wobble in orientation, distorting the direction of the outflows over time.
The stars of the serpents
The Serpens Nebula, located 1,300 light-years from Earth, is only one or two million years old, which is very young in cosmic terms. It is also home to a particularly dense cluster of newly forming stars (~100,000 years old) seen in the center of this image. Some of these stars will eventually grow to the mass of our Sun.
“Webb is a young stellar object finder,” Green said. “In this region, we collect signatures for every single young star, down to the lowest-mass stars.”
“It’s a very complete picture that we’re seeing now,” Pontoppidan added.
So, throughout the region of this image, the filaments and tufts of different hues represent reflected starlight from still-forming protostars in the cloud. In some areas there is dust in front of this reflection, which here appears with an orange, diffuse tint.
This region has been home to other serendipitous discoveries, including the wobbly “bat shadow,” which earned its name when 2020 data from NASA’s Hubble Space Telescope revealed that a star’s planet-forming disk was wobbling, or shifting. This feature is visible in the center of Webb’s image.
Future research
The new image and chance discovery of the aligned objects is actually just the first step in this scientific program. The team will now use Webb’s NIRSpec (Near-Infrared Spectrograph) to study the chemical composition of the cloud.
Astronomers are interested in determining how volatile chemicals survive the formation of stars and planets. Volatile substances are compounds that sublime or change from a solid directly to a gas at a relatively low temperature – including water and carbon monoxide. They will then compare their findings with amounts found in protoplanetary disks of similar-type stars.
“In the most elemental form, we are all made of matter derived from these volatile substances. Most of the water here on Earth originated when the Sun was a young protostar billions of years ago,” Pontoppidan said. “Looking at the abundance of these critical compounds in protostars just before their protoplanetary disks formed can help us understand how unique the circumstances were when our own solar system formed.”
These observations were made as part of the General Observer 1611 program. The team’s initial results have been accepted for publication in the Astrophysical Journal.
The James Webb Space Telescope is the world’s leading space science observatory. Webb solves mysteries in our solar system, looks beyond distant worlds around other stars, and explores the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners ESA (European Space Agency) and CSA (Canadian Space Agency).
