NASA’s Webb Peers into the Extreme Outer Galaxy

Among the Milky Way’s outskirts is a firecracker show of star formation

Released: 13th September, 2024, Academia Sinica, Institute of Astronomy & Astrophysics (ASIAA), Taiwan

How do environmental factors affect the star formation process?

To help answer this question, NASA’s James Webb Space Telescope examined the fringes of our Milky Way galaxy. This region is known as the Extreme Outer Galaxy, which lies over 58,000 light-years away from the Galactic Center. Webb’s near- and mid-infrared imaging capabilities enabled scientists to examine a star-forming area reminiscent to our galaxy during its early formation.

Astronomers have directed NASA’s James Webb Space Telescope to examine a rural area of our Milky Way galaxy. Scientists call this region the Extreme Outer Galaxy (EOG) due to its location more than 58,000 light-years away from the Galactic Center. (For comparison, Earth is approximately 26,000 light-years from the center.)

A team of scientists, working under time allocated to Mike Ressler of NASA’s Jet Propulsion Laboratory in California, used Webb’s NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) to image select regions within two molecular clouds known as Digel Clouds 1 and 2. With its high degree of sensitivity and sharp resolution, the Webb data resolved these areas, which are hosts to star clusters undergoing bursts of star formation, in unprecedented detail.

“In the past, we knew about these star forming regions but were not able to delve into their properties,” said Natsuko Izumi of Gifu University and the National Astronomical Observatory of Japan, who was a former postdoctoral fellow at the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), and the lead author of the study. “The Webb data builds upon what we have incrementally gathered over the years from prior observations with different telescopes and observatories. We can get very powerful and impressive images of these clouds with Webb. In the case of Digel Cloud 2, I did not expect to see such active star formation and spectacular jets.” Patrick Koch, a co-author of the study at ASIAA, adds: “Besides the stunning images that we are obtaining with Webb, this is also a unique opportunity for our postdoctoral fellows in Taiwan to collaborate with world-leading teams in the US.”

Stars in the Making

Although the Digel Clouds are within our galaxy, they are relatively poor in elements heavier than hydrogen and helium. This composition makes them similar to dwarf galaxies and our own Milky Way in its early history. Therefore, the team took the opportunity to use Webb to capture the activity occurring in four clusters of young stars within Digel Clouds 1 and 2: 1A, 1B, 2N, and 2S.

For Cloud 2S, Webb captured the main cluster containing young, newly formed stars. This dense area is quite active as several stars are emitting extended jets of material along their poles. Additionally, while scientists previously suspected a sub cluster might be present within the cloud, Webb’s imaging capabilities confirmed its existence.

“We know from studying other nearby star-forming regions that as stars form during their early life phase, they start emitting jets of material at their poles,” said Ressler, second author of the study and principal investigator of the observing program. “What was fascinating and astounding to me from the Webb data is that there are multiple jets shooting out in all different directions from this cluster of stars. It’s a little bit like a firecracker, where you see things shooting this way and that.”

The Saga of Stars

The Webb imagery skims the surface of the EOG and the Digel Clouds, and is just a starting point for the team. They intend to revisit the rural Milky Way to find answers to a variety of current mysteries, including the relative abundance of stars of various masses within EOG star clusters. This measurement, which is similar to taking a census of the different types of stars, can help astronomers understand how the environment can influence star formation.

“I’m interested in continuing to study how star formation is occurring in these regions. By combining data from different observatories and telescopes, we can examine each stage in the evolution process,” said Izumi. “We also plan to investigate circumstellar disks within the Extreme Outer Galaxy. We still don’t know why their lifetimes are shorter than in nearby star-forming regions. And of course, I’d like to understand the kinematics of the jets we detected in Cloud 2S.”

Though the story of star formation is complex and some chapters are still shrouded in mystery, Webb is gathering clues and helping astronomers unravel this intricate tale.

Scientists used NASA’s James Webb Space Telescope to examine select star-forming areas in the Extreme Outer Galaxy in near- and mid-infrared light. Within this star-forming region, known as Digel Cloud 2S, the telescope observed young, newly formed stars and their extended jets of material. This Webb image also shows a dense sea of background galaxies and red nebulous structures within the region. In this image, colors were assigned to different filters from Webb’s MIRI and NIRCam: red (F1280W, F770W, F444W), green (F356W, F200W), and blue (F150W; F115W). Image Credit: NASA, ESA, CSA, STScI, Michael Ressler (NASA-JPL)

More Information:

This research presented in a paper "Overview Results of JWST Observations of Star-forming Clusters in the Extreme Outer Galaxy” by Izumi et al. has appeared in the Astronomical Journal on July 10th, 2024.

Media Contact:

Dr. Patrick Koch, +886-2-2366-5478, pmkoch@asiaa.sinica.edu.tw

Dr. Mei-Yin Chou, +886-2-2366-5415, cmy@asiaa.sinica.edu.tw