In the binary system VW Hydra, the white dwarf acts like a vacuum cleaner: it pulls material from its companion, forming a glowing disk around itself. From time to time, this disk becomes unstable and erupts, much like a sink that overflows and suddenly spills water. TESS monitored three such eruptions and caught an odd detail: before each flare, the brightness first dipped, then shot up dramatically. This dip resembles the moment when the water in the sink nearly drains, only to surge back with double force.
By measuring how the star's brightness changed over time, astronomers saw that during the dip, the disk continued to slowly reshape. This helped them calculate the masses of both stars: the white dwarf weighs roughly as much as the Sun (between 0.6 and 1.0 solar masses), while its companion is a lightweight star with a mass of about 0.08–0.14 solar masses. Such precise data make VW Hydra a benchmark for testing models of eruptions in similar systems.
The white dwarf in VW Hydra is so dense that a teaspoon of its material would weigh several tons.
Eruptions on white dwarfs have inspired scenes in science fiction where characters witness sudden bursts of radiation from stars.