For the first time, a phenomenon that astronomers long hoped could be directly imaged has been captured by the Near-Infrared Camera (NIRCam) on NASA’s James Webb Space Telescope. In this stunning image of the Serpent Nebula, the discovery lies in the northern region (visible above left) of this young, nearby star-forming region.
Astronomers have discovered an intriguing group of protostellar outflows, which form when jets of gas spewing from newborn stars collide at high speed with nearby gas and dust. Usually these objects have different orientations within one area. Here, however, they run in the same direction and to the same extent, like sleet during a storm.
The discovery of these aligned objects, made possible by Webb’s exquisite spatial resolution and sensitivity in near-infrared wavelengths, provides information about the basic principles of how stars are born.
“Astronomers have long believed that as clouds collapse to form stars, the stars will tend to spin in the same direction,” said lead researcher Klaus Pontoppidan of NASA’s Jet Propulsion Laboratory in Pasadena, California. “However, this has never been seen so directly before. These aligned, elongated structures provide a historical record of the fundamental way stars are born.”
How does the alignment of the stellar jets relate to the star’s rotation? When an interstellar gas cloud collides with itself and forms a star, it spins faster. The only way for the gas to continue moving in 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 a vortex around a drain. The swirling magnetic fields in the inner disk launch some of the material into twin jets that shoot out in opposite directions, perpendicular to the material disk.
In the Webb image, these jets are indicated by bright clumpy streaks that appear red, which are shock waves from the jet hitting 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 – really comes into focus 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 looked like just blobs or were completely invisible in optical wavelengths due to the thick dust surrounding them.”
Astronomers say there are a number of forces that could 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, changing the direction of the outflow over time.
Stars of the Serpens
The Serpent Nebula, located 1,300 light-years from Earth, is only one to two million years old, which is very young cosmically. 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 young, great object search engine,” Green said. “In this field we pick up signposts from every young star, down to the lowest-mass stars.”
“It’s a very complete picture that we see now,” Pontoppidan added.
Throughout the region in this image, filaments and strings of varying hues represent reflected starlight from still-forming protostars in the cloud. In some places there is dust for that reflection, which appears here with an orange, diffuse tint.
This region was home to other accidental discoveries, including the fluttering “Bat Shadow,” which got its name when 2020 data from NASA’s Hubble Space Telescope revealed that a star’s planet-forming disk was flapping or shifting. This feature is visible in the center of the Webb image.
Future studies
The new image and the accidental 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 investigate the chemical composition of the cloud.
The astronomers are interested in determining how volatile chemicals survive the formation of stars and planets. Volatile substances are compounds that sublimate, or change directly from a solid to a gas, at a relatively low temperature, including water and carbon monoxide. They then compare their findings with the quantities found in protoplanetary disks of stars of the same type.
“At its most basic level, we are all made of matter that comes from these volatiles. Most of the water here on Earth was formed when the sun was still a young protostar billions of years ago,” says Pontoppidan. “Looking at the abundance of these crucial compounds in protostars just before their protoplanetary disks formed can help us understand how unique the conditions were when our own solar system formed.”
These observations were made as part of the General Observer program 1611. The team’s initial results have been accepted for publication in the Astrophysical Journal.
The James Webb Space Telescope is the world’s premier observatory for space science. Webb solves mysteries in our solar system, looks beyond to distant worlds around other stars and investigates 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).