Original title: NGC 1901: A new benchmark cluster for gyrochronology in the TESS Southern continuous viewing zone
Mara Bernizzoni, Timothy R. Bedding, Prasad Mani, Luke G. Bouma +4 · September 2026
Astronomers struggle to tell the exact ages of stars. To fix this, they use gyrochronologyDating stars by how fast they spin, since rotation slows with age., a method that dates stars by measuring how fast they spin, since stars slow down as they grow older. Researchers studied NGC 1901, a neglected star cluster located near the Large Magellanic Cloud on the sky. They tracked the spins of 32 member stars to calculate the cluster's age as 830 $\pm$ 50 Myr. This places it neatly between younger and older known benchmark clusters. They found that cooler stars, called late K dwarfs, stall and temporarily stop slowing down. This pause supports the idea that the stars' spinning cores reconnect with their outer envelopes. NGC 1901 now serves as an important benchmark cluster.
Imagine trying to guess a tree's age by counting its rings. Normally, trees in richer soil might grow rings faster, so soil type could make the age guess unreliable. In this paper, the star's rotation speed is like its rings, and they found that even with less metal (like poor soil), the age estimate still matches models, so the method works across different conditions.
Astronomers use star spin to estimate ages, and this shows metal content barely skews the method for Sun-like stars, making age-dating simpler. It gives them a new reference point in an age gap between known clusters.
The abstract does not establish if this works for all star types or clusters beyond NGC 1901. Spin-down stalling is only noted for late K dwarfs, and broader applicability is not proven. The study is limited to the TESS Southern continuous viewing zone.
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NGC 1901: A new benchmark cluster for gyrochronology in the TESS Southern continuous viewing zone — Mara Bernizzoni, Timothy R. Bedding, Prasad Mani et al.
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.