For the first time, a phenomenon that astronomers had long hoped to photograph directly has been captured by the James Webb Space Telescope’s Near Infrared Camera (NIRCam). In this stunning image of the Serpent Nebula, the discovery is located in the northern region (visible in the upper left) of this young nearby star-forming region.
Astronomers have discovered an interesting group of protostellar outflows, created when jets of gas spewing from newborn stars collide at high speed with nearby gas and dust. Typically, these objects have different orientations within a single area. Here, however, they are tilted in the same direction, to the same extent as the sleet that rolls in thunderstorms.
The discovery of these aligned objects, made possible by Webb’s superior 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 collapse to form stars, the stars tend to rotate in the same direction,” said lead researcher Klaus Pontoppidan of NASA’s Jet Propulsion Laboratory in Pasadena, California. “However, it has not yet been seen so directly. These aligned, elongated structures are a historical record of the fundamental way stars are born.”
So how does the alignment of star jets relate to the star’s rotation? When an interstellar cloud of gas collapses in on itself to form a star, it spins 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, which transports material downward, like an outflow vortex. Swirling magnetic fields in the inner disk shoot some of the material into two jets that shoot out in opposite directions, perpendicular to the material disk.
In the Webb image, these jets are marked by bright clumpy 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 region of the Serpens Nebula — Serpens North — is clearly visible 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 as mere blobs or were completely invisible at optical wavelengths due to the dense dust surrounding them.”
Astronomers say there are several forces that can potentially shift the direction of outflows during this period of a young star’s life. One way is when binaries rotate around each other and fluctuate in orientation, twisting the direction of the outflows over time.
Snake stars
Located 1,300 light-years from Earth, the Serpent Nebula 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 search engine,” Green said. “In this field, we collect the signatures of 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 area in this image, the filaments and tufts of different hues represent reflected starlight from the still-forming protostars in the cloud. In some areas there is dust in front of this reflection, which appears here with an orange, diffuse hue.
The area has been home to other serendipitous discoveries, including a fluttering “bat shadow,” which earned its name when 2020 data from NASA’s Hubble Space Telescope revealed that the disk of the planet-forming star was wobbly, or drifting. This feature is visible in the center of the Webb image.
Future studies
The new image and the serendipitous 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 investigate the cloud’s chemical composition.
Astronomers are interested in how volatile chemicals survive the formation of stars and planets. Volatiles are compounds that sublime or change from a solid directly to a gas at a relatively low temperature – including water and carbon monoxide. They then compare their findings with the abundances found in protoplanetary disks of similar-type stars.
“In our most basic form, we are all made of matter that comes from these volatiles.” Most of the water here on Earth formed when the Sun was a newborn protostar billions of years ago,” Pontoppidan said. “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 own 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 observatory for space science. Webb solves mysteries in our solar system, looks further to 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).