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كما كتبه المؤلفون، بالإنجليزية arXiv:2603.11194

Alpha Crucis is the closest very high multiplicity massive star to the Sun. At its heart is the $$4" \leftrightarrow 430 \text{ au}$$ binary $$\alpha^1$$ (A) + $$\alpha^2$$ (B) Cru, which combined make up the 13th visually brightest star in the night sky. Here we make use of archival VLTI data of $$\alpha$$ Cru A+B in order to study its multiplicity and orbital architecture. The data spatially resolved the close (6 mas) companion in $$\alpha$$ Cru A (a known spectroscopic binary) and revealed that $$\alpha$$ Cru B is also a close (17 mas) binary, which upgrades $$\alpha$$ Cru to a seven star system. By combining the interferometric data with radial velocities, we solve for the full orbit of Aa+Ab and find dynamical masses $$M_{Aa}=17.2\pm1.2 M_{\odot}$$ and $$M_{Ab}=6.8\pm0.3 M_{\odot}$$. While the data on Alpha Cru B are not yet sufficient to tightly constrain all orbital parameters, we find that the orbital period is most likely 405 days (with 203 days also a possibility). The orientation of the orbital planes are sufficiently constrained to yield a mutual inclination between Aa+Ab and Ba+Bb of either $$50 \pm 5^{\circ}$$ or $$137\pm5^{\circ}$$, pointing to a dynamical formation scenario for the system. The photometric masses $$M_{Ba}=12.4 M_{\odot}$$ and $$M_{Bb}=9.8 M_{\odot}$$ together with the less massive wide component $$\alpha$$ Cru Ca+Cb+D yield a total mass $$M\simeq52 M_{\odot}$$. At larger distances, the seven-star nature of Alpha Crucis would be arguably very challenging to unveil, suggesting that the companion frequency in massive star surveys may be underestimated.