Astronomers identified an exceptionally tiny core that may represent an early stage in the formation of a massive star. Located in an infrared-dark area called Dragon Cloud, the core is nicknamed the “dragon egg.” The paper, accepted for publication in Astronomy & Astrophysics, was posted to the arXiv preprint server on Oct. 5.
How massive stars form
How giant stars, with masses eight times greater than the sun, form is still a matter of debate in the scientific community. There are two main ideas. One says that a dense cloud of gas first condenses into a massive “pre-stellar” core, which then collapses to form a single giant star. Another says the star begins small and grows by pulling in material from the larger clump around it.
Researchers think that if they directly observe a compact, massive yet young concentration of mass, they will be able to lean toward one of these ideas. Such cores, however, are hard to detect, and if they are found, their interpretations are sometimes complicated by nearby star formation and stellar activity.
Astronomers observed one such promising candidate called C2c1a in the C2c1 region inside an infrared-dark cloud known as Dragon Cloud, located about 16,300 light-years away. Nicknamed the “dragon egg,” the core appears to contain some 20 to 30 times the sun’s mass. The clump around it holds roughly 1,061 times the mass of the sun but gives off little energy for its size. This, researchers say, is a sign of a “very early stage of high-mass star formation.” Earlier data could not confirm whether C2c1a is one compact object, where its mass is concentrated, or whether a protostar has formed.
In this study, the team led by Ashley Thomas Barnes of the European Southern Observatory (ESO) used new ALMA Band 6 observations to obtain a high-resolution view of the dragon egg. “These data are among the highest-resolution and most sensitive ALMA Band 6 observations currently available for similar targets,” researchers write in their paper.
A broken egg
High-resolution data revealed that the main region itself has six components: C2c1a(a), C2c1b, and four fainter structures in the intervening envelope. The emission was dominated by the central component C2c1a(a). This indicates that most of the emission comes from a centrally concentrated region. The core is embedded in a much larger reservoir of cold gas and dust with a mass of at least around 110 times the sun’s mass. This could supply the material needed to form a massive star.
Spectral analysis revealed little glowing gas at the center of C2c1a(a). There is some faint emission that is spread out. Researchers say this could be because the core is not hot. But it could also mean the dust is so thick that it blocks the glow. They also found no signs of any outflows such as energetic jets blown by the young star. “A weak, deeply embedded, or unfavorably oriented outflow cannot be excluded, but the present data reveal no clear outflow signature from the compact source,” researchers explain.
Earliest stages of formation
The researchers also compared how much light the clump emits relative to its mass. A low ratio below 1 typically implies the clump is young. The parent clump, Dragon Cloud, has a ratio of about 0.5, placing it in the group of young clumps.
Researchers say that its properties, even without strong stellar activity, fit the “initial conditions of monolithic core-accretion models,” but are careful to note that these observations are not enough to distinguish it from pathways where the source keeps gaining mass from its surroundings. They do not know the dust temperature accurately, which makes the nature of the core ambiguous. It could be a cold core with lots of mass or a warmer, less massive object within a larger reservoir of cold gas and dust.
Researchers suggest that, overall, C2c1a(a) provides a rare view of the “earliest stages of collapse and mass assembly” inside a possibly cold cloud.
Written for you by our author Shreejaya Karantha, edited by Lisa Lock, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive.
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Publication details
A. T. Barnes et al., Cracking open the “dragon egg”: ALMA 1.3mm observations of a compact, young high-mass core candidate at 30mas resolution, arXiv (2026). DOI: 10.48550/arxiv.2610.07138
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ALMA spots ‘dragon egg’ that may represent the earliest stages of massive star formation (2026, October 23)
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