A star’s secret history: Hubble telescope spots white dwarf formed from violent stellar collision, not time

A white dwarf colliding with a red giant can create a bow shock strong enough to peel away its outer layers, exposing the hidden carbon core. A new study suggests that the star WD 0525+526 likely formed this way, instead of following the usual evolutionary path of a single star. (Image: NASA/ ESA/STScI/ Ralf Crawford)

What looked like an ordinary star has revealed a violent past. Astronomers using the Hubble Space Telescope discovered that a white dwarf, once thought normal, is actually the remnant of two colliding stars.

White Dwarf with Unusual Origins

The star, named WD 0525+526, lies about 128 light-years away. At first, it appeared like any other white dwarf seen in visible light. But Hubble’s ultraviolet observations told a different story. Scientists identified anomalous levels of carbon in its atmosphere, an unmistakable indicator of a star merger. Normally, white dwarfs are covered with hydrogen and helium, which mask their carbon-rich interiors. Here, the cataclysmic collision removed the outer layers, revealing carbon.

Astronomers Detect Hidden Carbon Signals

The study, led by Snehalata Sahu and Boris Gaensicke from the University of Warwick, showed WD 0525+526 is hotter and more massive than most merger remnants. Its surface temperature reaches nearly 21,000 Kelvin and its mass is 1.2 times that of the sun. These features set it apart from the small number of similar stars already known.

Clues to Future Stellar Research

Because the star looked normal in visible light, astronomers now suspect that many other white dwarfs may conceal similar origins. The findings suggest that violent mergers could be more common than previously thought. Researchers plan to expand the study to see how many such stars exist and how these mergers may influence future supernovae. The discovery is detailed in the journal Nature Astronomy.