TESS Reveals that the Nearby Pisces–Eridanus Stellar Stream is only 120 Myr Old

Abstract Pisces–Eridanus (Psc–Eri), a nearby ( d ≃ 80–226 pc) stellar stream stretching across ≈120° of the sky, was recently discovered with Gaia data. The stream was claimed to be ≈1 Gyr old, which would make it an exceptional discovery for stellar astrophysics, as star clusters of that age are rare and tend to be distant, limiting their utility as benchmark samples. We test this old age for Psc–Eri in two ways. First, we compare the rotation periods for 101 low-mass members (measured using time-series photometry from the Transiting Exoplanet Survey Satellite ) to those of well-studied open clusters. Second, we identify 34 new high-mass candidate members, including the notable stars λ Tauri (an Algol-type eclipsing binary) and HD 1160 (host to a directly imaged object near the hydrogen-burning limit). We conduct an isochronal analysis of the color–magnitude data for these highest-mass members, again comparing our results to those for open clusters. Both analyses show that the stream has an age consistent with that of the Pleiades, i.e., ≈120 Myr. This makes the Psc–Eri stream an exciting source of young benchmarkable stars and, potentially, exoplanets located in a more diffuse environment that is distinct from that of the Pleiades and of other dense star clusters.