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The broken-exponential radial structure and larger size of the Milky Way galaxy
Imig, Julie; Chen, Bingqiu; Wang, Tao +4 more
The radial structure of a galaxy is a fundamental property that reflects its growth and assembly history. Although it is straightforward to measure that of external galaxies, it is challenging for the Milky Way because of our inside perspective. Traditionally, the radial structure of the Milky Way has been assumed to be characterized by a single-e…
An abrupt change in the stellar spin-down law at the fully convective boundary
Angus, Ruth; Amard, Louis; See, Victor +2 more
Unlike partially convective stars such as the Sun, fully convective stars do not possess a radiative core. Whether a star needs this core to generate a solar-like magnetic dynamo is still unclear. Recent studies suggest fully and partially convective stars exhibit very similar period-activity relationships, hinting that dynamos generated by stars …
Enrichment by extragalactic first stars in the Large Magellanic Cloud
Li, Ting S.; Frebel, Anna; Simon, Joshua D. +8 more
The Large Magellanic Cloud (LMC) is the Milky Way's most massive satellite galaxy, which only recently (~2 billion years ago) fell into our Galaxy. As stellar atmospheres preserve the composition of their natal cloud, the LMC's recent infall makes its most ancient, metal-deficient (`low-metallicity') stars unique windows into early star formation …
Insights into star formation and dispersal from the synchronization of stellar clocks
Alves, João; Barrado, David; Burkert, Andreas +3 more
Age is one of the most fundamental parameters of a star, yet it is one of the hardest to determine as it requires modelling various aspects of stellar formation and evolution. When we compare the ages derived from isochronal and dynamical traceback methods for six young stellar associations, we find a systematic discrepancy. Specifically, dynamica…
A seven-Earth-radius helium-burning star inside a 20.5-min detached binary
Filippenko, Alexei V.; Han, Zhanwen; Chen, Xuefei +28 more
Binary evolution theory predicts that the second common envelope ejection can produce low-mass (0.32-0.36 M⊙) subdwarf B (sdB) stars inside ultrashort-orbital-period binary systems, as their helium cores are ignited under nondegenerate conditions. With the orbital decay driven by gravitational-wave (GW) radiation, the minimum orbital pe…
The accretion of a solar mass per day by a 17-billion solar mass black hole
Wolf, Christian; Lai, Samuel; Bian, Fuyan +5 more
Around a million quasars have been catalogued in the Universe by probing deeper and using new methods for discovery. However, the hardest ones to find seem to be the rarest and brightest specimens. Here we study the properties of the most luminous of all quasars found so far. These have been overlooked until recently, which demonstrates that moder…
Detection of an Earth-sized exoplanet orbiting the nearby ultracool dwarf star SPECULOOS-3
Ikuta, Kai; Triaud, Amaury H. M. J.; Tamura, Motohide +82 more
Located at the bottom of the main sequence, ultracool dwarf stars are widespread in the solar neighbourhood. Nevertheless, their extremely low luminosity has left their planetary population largely unexplored, and only one of them, TRAPPIST-1, has so far been found to host a transiting planetary system. In this context, we present the SPECULOOS pr…
A slightly oblate dark matter halo revealed by a retrograde precessing Galactic disk warp
Huang, Yang; Liu, Jifeng; Beers, Timothy C. +7 more
The shape of the dark matter (DM) halo is key to understanding the hierarchical formation of the Galaxy. Despite extensive efforts in recent decades, however, its shape remains a matter of debate, with suggestions ranging from strongly oblate to prolate. Here, we present a new constraint on its present shape by directly measuring the evolution of …