In this image of the Serpens Nebula taken by NASA’s James Webb Space Telescope’s Near-Infrared Camera (NIRCam), astronomers discovered a cluster of aligned protostellar outflows in a small area (upper left corner). In the Webb image, these jets are marked by bright, clumpy streaks that appear red. These are shock waves created when the jet hits surrounding gas and dust. Image credit: NASA, ESA, CSA, STScI, Klaus Pontoppidan (NASA-JPL), Joel Green (STScI)
Alignment of bipolar jets confirms theories of star formation
Some of the greatest and most interesting astronomical discoveries have surprised researchers even when they examined the best-studied areas of the sky.
Often it is new technologies or coincidental timing that lead to these discoveries. In a new study of the Serpens Nebula with NASA‘S James Webb Space Telescopeit is both.
In one area of the nebula, Webb previously resolved blurry patches into sharp protostellar outflows. And to the researchers’ great surprise, these outflows appear to be in a line. This suggests that we have captured this area at a unique time in its history and provides us with information about the basics of star formation.
First discovery of its kind in stunning new image from the Webb Space Telescope
For the first time, a phenomenon that astronomers have long hoped to image 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 lies in the northern portion (seen at upper left) of this young, nearby star-forming region.
Astronomers have discovered a fascinating group of protostellar outflows, formed when jets of gas ejected by newborn stars collide at high speeds with nearby gas and dust. Normally these objects have different orientations within a region, but here they are tilted in the same direction, to the same extent as sleet pouring down during a storm.
The discovery of these aligned objects, made possible by the Webb telescope’s excellent spatial resolution and sensitivity at near-infrared wavelengths, provides information on the fundamentals of star formation.
“Astronomers have long assumed that when clouds collapse and stars form, the stars tend to rotate in the same direction,” said lead investigator Klaus Pontoppidan of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “But this has never been observed so directly. These aligned, elongated structures are a historical record of the fundamental way stars are born.”
This image from NASA’s James Webb Space Telescope shows part of the Serpens Nebula, where astronomers discovered a collection of aligned protostellar outflows. These jets are characterized by bright, clumpy streaks that appear red. These are shock waves created when the jet hits surrounding gas and dust. Here, the red color represents the presence of molecular hydrogen and carbon monoxide. Image credit: NASA, ESA, CSA, STScI, Klaus Pontoppidan (NASA-JPL), Joel Green (STScI)
The mechanics of star formation
So how does the orientation of the star’s jets relate to the star’s rotation? When an interstellar cloud of gas collides to form a star, it spins faster. The gas can only move further inward if some of the spin (called angular momentum) is removed. A disk of matter forms around the young star, carrying the material downward, like a whirlpool around a drain. The swirling magnetic fields in the inner disk hurl some of the material into twin jets that shoot outward in opposite directions, perpendicular to the disk of matter.
In the Webb image, these jets are characterized by bright, clumpy streaks that appear red. These are shock waves created when the jet hits surrounding gas and dust. Here, the red color represents the presence of molecular hydrogen and carbon monoxide.
This image shows the center of the Serpens Nebula as seen by the Near-Infrared Camera (NIRCam) on NASA’s James Webb Space Telescope. In this image, filaments and streaks of various hues throughout the region represent reflected starlight from still-forming protostars within the cloud. In some areas, dust is in front of this reflection, appearing here in an orange, diffuse hue. Image credit: NASA, ESA, CSA, STScI, Klaus Pontoppidan (NASA-JPL), Joel Green (STScI)
Improved imaging techniques
“This area of the Serpens Nebula – Serpens North – is only clearly seen with Webb,” said lead author Joel Green of the Space Telescope Science Institute in Baltimore. “We can now capture these extremely young stars and their outflows, some of which previously appeared only as specks or were completely invisible at optical wavelengths due to the dense dust surrounding them.”
Astronomers say there are some forces that can potentially change the direction of the outflows during this phase of a young star’s life. One possibility is that binary stars rotate around each other and fluctuate their orientation, causing the direction of the outflows to change over time.
This image of the Serpens Nebula, taken with the Near Infrared Camera (NIRCam) on the American Webb Space Telescope, shows compass arrows, scale, and color legend for reference.
The compass arrows for north and east show the orientation of the image in the sky. Note that the relationship between north and east in the sky (seen from below) is reversed compared to the direction arrows on a map of the ground (seen from above).
The scale is given in light years, which is the distance that light travels in one Earth year. One light year is approximately 5.88 trillion miles or 9.46 trillion kilometers.
This image shows invisible near-infrared light wavelengths converted to visible light colors. The color legend shows which NIRCam filters were used in collecting the light. The color of each filter name is the visible light color used to represent the infrared light passing through that filter.
Photo credits: NASA, ESA, CSA, STScI, Klaus Pontoppidan (NASA-JPL), Joel Green (STScI)
Stars of the Serpens Nebula
The Serpens Nebula, 1,300 light-years from Earth, is only one to two million years old, which is very young by cosmic standards. It is also home to a particularly dense cluster of newly forming stars (~100,000 years old), visible in the center of this image. Some of these stars will eventually reach the mass of our Sun.
“Webb is a machine for detecting young stellar objects,” Green said. “In this field, we find evidence of every single young star, down to the lowest mass stars.”
“We now see a very complete picture,” Pontoppidan added.
Throughout the region of this image, filaments and strands of various hues represent reflected starlight from still-forming protostars within the cloud. In some areas, dust lies in front of this reflection, appearing here in an orange, diffuse hue.
Other serendipitous discoveries have also been made in this region, including the fluttering “bat shadow,” which got its name when NASA data from 2020 Hubble Space Telescope showed that the planet-forming disk of a star wobbles or shifts. This phenomenon is visible in the center of the Webb image.
Path to future research
The new image and the serendipitous discovery of the aligned objects are actually just the first step in this science program. The team will now use Webb’s NIRSpec (near-infrared spectrograph) to study the chemical composition of the cloud.
The astronomers want to find out how volatile chemicals survive the formation of stars and planets. Volatiles are compounds that sublimate or change directly from a solid to a gaseous state at relatively low temperatures – including water and carbon monoxide. They will then compare their results with the amounts found in protoplanetary disks of similar stars.
“In their most basic form, we are all made of matter that arose from these volatiles. Most of the water here on Earth was formed when the Sun was a young protostar billions of years ago,” Pontoppidan said. “Looking at the abundance of these important 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 carried out as part of the General Observer program 1611. The team’s first results were submitted for publication in Astrophysical Journal.
The James Webb Space Telescope (JWST) is a large space-based observatory launched in December 2021. It is the scientific successor to the Hubble Space Telescope. Equipped with a 6.5-meter primary mirror, the JWST specializes in observing the Universe in the infrared spectrum, allowing it to look further back in time than ever before. This capability will allow the telescope to study the formation of the first galaxies, the evolution of stars and planetary systems, and the atmospheres of distant exoplanets. Located at the second Lagrange point (L2), about 1.5 million kilometers from Earth, the JWST is designed to offer unprecedented resolutions and sensitivities, opening new windows into the cosmos.