For the first time, a phenomenon that astronomers have long hoped to image directly has been captured by NASA’s James Webb Telescope Near Infrared Camera (NIRCam). In this stunning image of the Serpens Nebula, the discovery lies in the northern region (seen in the upper left) of this young region, close to star formation.
Astronomers found an intriguing array 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 different orientations within a region. Here, however, they are sloping in the same direction, at the same rate, as rain falling during a storm.
The discovery of these aligned objects, made possible by Webb’s fine spatial resolution and sensitivity at near-infrared wavelengths, is providing insight into the basics of how stars are born.
“Astronomers have long assumed that as clouds collapse to form stars, the stars will tend to rotate in the same direction,” said principal investigator Klaus Pontoppidan, of NASA’s Jet Propulsion Laboratory in Pasadena, California. “However, this has not been seen so directly before. These elongated, aligned structures are a historical record of the fundamental way stars are born.”
So how does the alignment of the stellar planes relate to the rotation of the star? As a cloud of interstellar gas collides with itself to form a star, it rotates faster. The only way for the gas to continue moving inward is to remove some of the spin (known as angular momentum). A disk of material forms around the young star to transport material downward, like an eddy around a drain. The rotating magnetic fields in the inner disc launch some of the material into twin jets that shoot out in opposite directions, perpendicular to the material disc.
In Webb’s image, these jets are signified by bright clustered streaks 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 area of the Serpens Nebula — Serpens North — comes into sharp view only 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 only as dots or were completely invisible at optical wavelengths due to the thick dust surrounding them.”
Astronomers say there are several forces that could potentially change the direction of outflows during this period of a young star’s life. One way is when binary stars orbit each other and oscillate 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 a million or two years old, which is very young in cosmic terms. It is also home to a particularly dense cluster of newly formed 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 new machine for finding stellar objects,” Green said. “In this field, we get the signatures of every 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 in this image, filaments and filaments of different hues represent reflected starlight from protostars still forming within the cloud. In some areas, there is dust in front of that reflection, which appears here with a diffuse orange tint.
This region has been home to other serendipitous discoveries, including the colliding “Bat Shadow,” which got its name when 2020 data from NASA’s Hubble Space Telescope revealed that the disc of a planet of a the star that formed the planet collided or moved. This feature is visible in the center of Webb’s image.
Future studies
The new image, and the remarkable discovery of aligned objects, is actually just the first step in this scientific program. The team will now use Webb’s NIRSpec (Near Infrared Spectrograph) to probe the chemical composition of the cloud.
Astronomers are interested in determining how unstable chemicals survive the formation of stars and planets. Volatiles are compounds that sublimate, 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 the quantities found in the protoplanetary disks of similar-type stars.
“In the most basic form, we are all made of matter that comes from these volatiles. Most of the water here on Earth originated when the Sun was a baby protostar billions of years ago,” said Pontoppidan. “Looking at the abundance of these critical compounds in protostars just before their protoplanetary disks formed could help us understand how unique the circumstances were when our solar system formed.”
These observations were taken 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 is solving mysteries in our solar system, peering beyond distant worlds around other stars, and investigating 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).