For the first time, a team of Japanese astronomers has captured clear images of jets and outflows from a young star forming in the far reaches of our Milky Way.
Using the powerful Atacama Large Millimeter/submillimeter Array (ALMA) — an observatory in Chile comprising 66 antennas, they observed the protostar Sh 2-283-1a SMM1. This young star is located nearly 26,000 light-years from the sun and 51,000 light-years from our galaxy’s center.
Until now, scientists had struggled to capture resolved details of such distant stars because the structures are small, faint, and require extremely sharp telescopes. ALMA’s precision finally made it possible.
“This discovery unlocks a unique opportunity to fundamentally advance our understanding of how stars are born across diverse cosmic environments,” Toki Ikeda, first study author and a researcher at Niigata University, said.
Detecting the jets of a distant protostar
The researchers pointed ALMA toward Sh 2-283-1a SMM1, a young star still wrapped in its birth cloud of gas and dust. What they noticed was mesmerizing—narrow, high-speed jets of gas blasting out from the star in opposite directions, surrounded by slower-moving, broader outflows.
To map the motions, the team tracked the gas flowing toward Earth (blue contours) and away from Earth (red contours). A closer look at the velocity of this gas revealed that the jets don’t flow continuously. Instead, they are episodic bursts of material, occurring every 900 to 4,000 years.
This stop-and-start rhythm plays a key role in how stars grow, allowing the star to feed on material from its surrounding disk while shedding excess mass and spin. Episodic ejections had been observed in nearby star-forming regions, but this is the first time they have been resolved in a star more than 15 kiloparsecs (~51,000 light-years) from the galactic center.
The chemical makeup of the system told another story. By measuring carbon monoxide (CO) and silicon monoxide (SiO), the team found that the ratio of SiO to CO was lower than in similar inner-galaxy stars.
“This suggests that shock chemistry or dust properties differ in the outer galaxy, where heavy elements are scarce. The finding reinforces that the physics of star formation is universal, whereas the chemistry varies depending on the local conditions,” the researchers note.
The protostar itself is extraordinary. The team estimated its brightness at about 6,700 times that of the Sun, characteristic of an intermediate-to-high-mass star. They also found signs of a hot core, a warm and chemically rich region close to the star.
Such hot cores are rare in the outer galaxy. This is only the second of its kind detection, making Sh 2-283-1a SMM1 an especially valuable target. “Finding such a clean jet structure in the outer galaxy was unexpected,” Takashi Shimonishi, one of the study authors, said.
What’s even more surprising is that ALMA picked up hints of complex organic molecules in the system, opening a window into the chemistry that might eventually seed new planets. Beyond this star, ALMA also detected molecular outflows from four additional protostars, confirming that star formation is widespread even in these remote, chemically primitive regions.
Same physics but different chemistry
This discovery proves that the blueprint of star formation is the same across the galaxy, no matter how rich the environment is in heavy elements. “By resolving jets and outflows in a protostar so far out in the galaxy, we can see that the same physics shaping stars near the sun also operates in low-metallicity environments,” Ikeda added.
At the same time, the differences in chemical fingerprints show that local conditions shape the ingredients available for stars and planets. This means studying outer-galaxy stars doesn’t just teach us about our Milky Way; it gives us clues to how the earliest generations of stars in the universe formed.
The research also highlights ALMA’s power in pushing the boundaries of astronomy. Until now, resolved jets and outflows had only been seen in stars a few thousand light-years away. Extending this to 51,000 light-years opens up new possibilities.
The team now plans to study more protostars in the outer galaxy to see if ejection cycles or molecular chemistry change with metallicity.
The study is published in The Astrophysical Journal.