For the first time, the Near Infrared Camera (NIRCam) on NASA’s James Webb Space Telescope has captured a phenomenon that astronomers have long hoped to observe directly. In this stunning image of the Serpens Nebula, the discovery is in the northern zone (seen at top left) of this young, nearby star-forming region.
Astronomers found an intriguing group of protostellar jets, which form when gas jets erupting from newborn stars collide at high speed with nearby gas and dust. Normally, these objects have varied orientations within the same region. Here, however, they are tilted in the same direction, to the same degree, like sleet that falls during a storm.
The discovery of these aligned objects, made possible by Webb’s exquisite spatial resolution and sensitivity at near-infrared wavelengths, is providing insights into the fundamentals of how stars are born.
“Astronomers have long assumed that when clouds collapse to form stars, they tend to spin in the same direction,” explains Klaus Pontoppidan, principal investigator at 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 fundamental way stars are born.”
What is the relationship between the alignment of the stellar jets and the rotation of the star? When a cloud of interstellar gas crashes into itself to form a star, it rotates more rapidly. 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 the material downward, like a whirlpool around a drain. Swirling magnetic fields in the inner disk launch some of the material in twin jets that shoot outward in opposite directions, perpendicular to the disk of material.
In the Webb image, these jets are characterized by bright, lumpy red streaks, which are shock waves from the jet against the surrounding gas and dust. In this case, the color red represents the presence of molecular hydrogen and carbon monoxide.
“This area of the Serpens Nebula – North Serpens – is only seen clearly with the Webb,” explains Joel Green, lead author 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 thick dust surrounding them.”
Astronomers say there are some forces that can change the direction of the outflows during this period of a young star’s life. One is when binary stars rotate around each other and wobble in their orientation, twisting the direction of the outflows over time.
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 an especially dense cluster of newly formed stars (about 100,000 years old), seen in the center of this image. Some of these stars will eventually reach the mass of our Sun.
Thus, throughout the region of this image, filaments and spirals of different hues represent the reflected starlight from protostars still forming within the cloud. In some areas, there is dust in front of that reflection, which here appears with a diffuse orange tone.
This region has been the scene of other serendipitous discoveries, such as the “bat shadow” flutter, which earned its name when 2020 data from NASA’s Hubble Space Telescope revealed that a star’s planetary-forming disk was waved, or moved. This feature is visible in the center of the Webb image.
NASA, ESA, CSA, K. Pontoppidan (NASA’s Jet Propulsion Laboratory) and J. Green (Space Telescope Science Institute).
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