NASA

NASA’s Webb Peers into the Extreme Outer Galaxy

Ben09/14/2024

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Astronomers have directed NASA’s James Webb Space Telescope to examine the outskirts of our Milky Way galaxy. Scientists call this region the Extreme Outer Galaxy 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 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. Details of this data include components of the clusters such as very young (Class 0) protostars, outflows and jets, and distinctive nebular structures.

These Webb observations, which came from telescope time allocated to Mike Ressler of NASA’s Jet Propulsion Laboratory in Southern California, are enabling scientists to study star formation in the outer Milky Way in the same depth of detail as observations of star formation in our own solar neighborhood.

“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, 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.”

Image A: Extreme Outer Galaxy (NIRCam and MIRI)

At center right is a compact star cluster composed of luminous red, blue, and white points of light. Faint jets with clumpy, diffuse material extend in various directions from the bright cluster. Above and to the right is a smaller cluster of stars. Translucent red wisps of material stretch across the scene, though there are patches and a noticeable gap in the top left corner that reveal the black background of space. Background galaxies are scattered across this swath of space, appearing as small blue-white and orange-white dots or fuzzy, thin disks. There are two noticeably larger points, foreground stars, with diffraction spikes: an orange-white point on the left, and a blue-white point in the top right.

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).

NASA, ESA, CSA, STScI, M. Ressler (JPL)

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 for the first time.

“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 Extreme Outer Galaxy and the Digel Clouds, and is just a starting point for the team. They intend to revisit this outpost in the Milky Way to find answers to a variety of current mysteries, including the relative abundance of stars of various masses within Extreme Outer Galaxy star clusters. This measurement can help astronomers understand how a particular environment can influence different types of stars during their 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 star-forming regions much closer to us. 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.

These findings have been published in the Astronomical Journal.

The observations were taken as part of Guaranteed Time Observation program 1237.

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing 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).