Discovery of Coaligned Protostellar Outflows Sheds Light on Star Formation

A team of astronomers from NASAS's Jet Propulsion Laboratory has discovered a fascinating collection of protostellar outflows and captured the image directly using the Near-Infrared Camera (NIRCam) on NASA's James Webb Space Telescope. The study has been published in Astrophysical Journal.

Astronomers discovered a fascinating collection of protostellar outflows. These outflows are created when fast-moving gas jets from young stars collide with surrounding gas and dust. These objects usually have different orientations within the same area. Here, though, they are tilted to the same extent and in the same direction, similar to sleet falling during a storm.

The discovery of these aligned objects, enabled by Webb's exceptional spatial resolution and sensitivity in near-infrared wavelengths, offers insights into the fundamentals of star formation.

Astronomers have long assumed that as clouds collapse to form stars, the stars will tend to spin in the same direction. However, this has not been seen so directly before. These aligned, elongated structures are a historical record of the fundamental way that stars are born.

Klaus Pontoppidan, Principal Investigator, Jet Propulsion Laboratory, NASA

The relationship between the star's rotation and the alignment of its jets is analyzed. An interstellar gas cloud spins faster as it collides with itself to form a star. Removing some of the spin, or angular momentum, is the only way the gas can keep moving inward. Like a vortex around a drain, a disk of material forms around the young star to carry material downward. A portion of the material is propelled into twin jets that shoot outward in opposite directions, perpendicular to the material disk, by the whirling magnetic fields within the inner disk.

These jets are identified in the Webb image by red, clumpy, bright streaks resulting from the jet's shockwaves striking nearby gas and dust. In this instance, the color red indicates the presence of molecular hydrogen and carbon monoxide.

This area of the Serpens Nebula–Serpens North–only comes into clear view with Webb. We’re now able to catch these extremely young stars and their outflows, some of which previously appeared as just blobs or were completely invisible in optical wavelengths because of the thick dust surrounding them.

Joel Green, Study Lead Author, Space Telescope Science Institute

Astronomers believe a few factors may be able to change the direction of the outflows during this stage of a young star's life. One mechanism is that over time, the direction of the outflows is twisted as binary stars wobble in orientation and spin around each other.

Stars of the Serpens

In cosmic terms, the Serpens Nebula, which is 1,300 light-years away from Earth, is relatively young, having only been around for one or two million years. At the center of this image is a particularly dense cluster of recently formed stars, estimated to be around 100,000 years old. At some point, a few of these stars will reach the mass of the Sun.

Green said, “Webb is a young stellar object-finding machine.”

In this field, we pick up sign posts of every single young star, down to the lowest mass stars. It’s a very complete picture we’re seeing now.

Klaus Pontoppidan, Principal Investigator, Jet Propulsion Laboratory, NASA

Thus, filaments and wisps of various colors in this image's region correspond to reflected starlight from still-forming protostars inside the cloud. The reflection appears here diffusely orange, with dust in front of it in some places.

Other coincidental discoveries have been made in this area, such as the flapping "Bat Shadow," which got its name when NASA's Hubble Space Telescope data from 2020 showed that a star's planet-forming disk was shifting, or flapping. The Webb image's center displays this feature.

Future Studies

The alignment of the objects and the creation of this new image are only the beginning of this scientific program. The team will now examine the cloud's chemical composition using Webb's NIRSpec (Near-Infrared Spectrograph).

Astronomers are intrigued by how volatile chemicals survive the formation of stars and planets. Volatiles include substances like water and carbon monoxide that sublimate or change instantly from a solid to a gas at a comparatively low temperature. Astronomers will then compare the amounts they discover to those in protoplanetary disks of stars of a similar type.

Pontoppidan said, “At the most basic form, we are all made of matter that came from these volatiles. The majority of water here on Earth originated when the Sun was an infant protostar billions of years ago. Looking at the abundance of these critical compounds in protostars just before their protoplanetary disks have formed could help us understand how unique the circumstances were when our own solar system formed.”

These observations were conducted as part of General Observer program 1611.

A Tour of The Serpens Nebula. Video Credit: Space Telescope Science Institute

Journal Reference:

Pontoppidan, M., K., et al. (2022) The JWST Early Release Observations. The Astrophysical Journal Letters. doi.org/10.3847/2041-8213/ac8a4e