Predictions of stellar occultations by Haumea and the event of 2026 May 4

ABSTRACT Haumea is the third largest of the five officially recognized dwarf planets and one of the four that reside in the trans-Neptunian region. It is among the most exotic bodies in the Solar system. Because of its large distance, direct exploration by space missions is not feasible in the short term, so progress must rely on ground- and near-Earth facilities. Stellar occultations are among the most powerful tools to investigate trans-Neptunian objects. We present predictions of occultations by Haumea in the coming years for stars down to Gaia G = 21. We identify eleven relevant events through 2030. We analysed in detail the geometry of the 2026 May 4 event, including Haumea’s rotation phase, known 3D shape, pole orientation, and sky-plane motion. We derive a sky-plane shadow width of 2224 $\pm$ 30 km, substantially larger than nominal assumptions and therefore highly favourable for observations. Given the star’s large RUWE of 6.6, raising concerns about the detectability of the event, we also performed a reliability analysis. Speckle imaging reveals a companion at $\sim$0.12 arcsec and $\Delta m \approx 3.1$; this companion is also expected to be occulted, and shifts the nominal main-star path prediction on Earth by about 8 mas.