White Dwarf Plays Hide-and-Seek with Cosmic Dust ⚡ экспресс
The discovery of deep irregular periodic transits around the white dwarf ZTF J1944+4557 is presented, based on photometry and spectroscopy from the Palomar, Keck, McDonald, Perkins, and Lowell observatories. The primary period is 4.9704 hours, close to the Roche limit; individual dips deeper than 30% last 15–40 minutes. As with WD 1145+017, transit events are clearly separated by phases without attenuation. Spectroscopy during transits shows a constant equivalent width of the Ca K line; broadening of absorption features is not reproduced by photospheric models, indicating circumstellar gas. Simultaneous observations in g+r and g+i filters with the CHIMERA instrument revealed no color dependence of the depths, requiring dust grains ≳0.2 µm in size. The morphology of transits changes faster than the orbital period; in 2024, activity completely vanished for seven months, reappearing in March 2025 with the same period. The complete cessation and resumption of eclipses provide a unique laboratory for constraining the evolution of destroyed material and the depletion and replenishment timescales of the disk.
A dead star the size of Earth — a white dwarf, first spotted by William Herschel back in 1783 — has decided to play hide-and-seek. The ZTF telescope, heir to the ideas of Fritz Zwicky, caught it undergoing eclipses every 4 hours 58 minutes: the light drops by a third. The culprits: clouds of cosmic dust. Precise brightness measurements show the dust grains are larger than smoke particles, because they dim both blue and red light equally. Splitting light into colors reveals hot gas — the remains of a shredded asteroid.
The game is rigged: the pattern of eclipses changes faster than the clouds complete one orbit. In 2024, they disappeared entirely for seven months, only to return and block the star again in 2025. This isn't just hide-and-seek — it's the death throes of a planetary system, where a dusty ring is born and dies before our eyes.
🎯 The 4.97-hour orbital period is so short that one 'year' for these dust clouds lasts less than a polar day in Murmansk.