The Universe still holds many surprises, as demonstrated by this exceptional observation of a dying star devouring the remains of its own planetary system. This phenomenon, captured by some of the world's most powerful telescopes, opens a unique window into the fate of worlds orbiting stars similar to our Sun.
Located 145 light-years away from us, the white dwarf star LSPM J0207+3331 represents the residual core of a star that was once similar to our Sun. After going through its red giant phase three billion years ago, this star expelled its outer layers, leaving only a dense and incandescent core. Spectroscopic observations conducted with the Magellan telescopes in Chile and the Keck telescopes in Hawaii reveal that planetary fragments survived this violent stellar transformation.
Artist's representation of a debris disk with solid bodies around a white dwarf.
Credit: NASA/ESA/Joseph Olmsted (STScI) Spectroscopic analysis detected no fewer than thirteen different chemical elements coming from a celestial object in the process of destruction. Among these elements are aluminum, carbon, chromium, cobalt, copper, iron, magnesium, manganese, nickel, silicon, sodium, strontium, and titanium, whose proportions strangely resemble those found on Earth. The simultaneous presence of all these elements indicates that matter accretion onto the white dwarf occurred recently, probably within the last 35,000 years, and might even be ongoing currently.
The white dwarf is also surrounded by a silicate-rich debris disk, detected by NASA's WISE space telescope through its characteristic infrared emission. Future observations with the James Webb Space Telescope could analyze the mineralogical composition of this disk and estimate its total mass, thus providing valuable clues about the exact nature of the original planetary system.
The central question puzzling scientists concerns the timing of this destructive event. Why was this object drawn toward the white dwarf now, after three billion years of relative stability? Érika Le Bourdais, lead author of the study published in
The Astrophysical Journal, explains that this continuous accretion suggests that white dwarfs might retain planetary remnants still subject to dynamic changes. Gravitational perturbations caused by possible surviving gas giant planets could explain this late instability, a hypothesis that the European Space Agency's Gaia mission could verify as early as 2026.
The life cycle of Sun-like stars
Solar-type stars follow a well-defined evolutionary path spanning billions of years. After burning their hydrogen during the main sequence, they enter a phase of spectacular expansion called the red giant phase, during which their diameter can increase several hundred times.
This radical transformation is accompanied by the expulsion of the star's outer layers, sometimes creating beautiful planetary nebulae. The residual core, deprived of its nuclear reactions, then contracts under the effect of its own gravity to form a white dwarf, an extremely dense object where a teaspoon of matter would weigh several tons on Earth.
The surface temperature of a white dwarf can initially exceed 100,000 degrees Celsius, but it gradually cools over cosmological timescales. This slow cooling allows astronomers to estimate the age of these stellar objects and trace the history of the planetary systems that surrounded them.
The discovery of LSPM J0207+3331 shows that even after this complete stellar transformation, the gravitational influence of white dwarfs continues to shape the evolution of surviving celestial bodies in their immediate environment.
Spectroscopy: a window into the composition of celestial bodies
Astronomical spectroscopy represents one of the most powerful techniques for analyzing the chemical composition of distant celestial objects. This method relies on analyzing light emitted or absorbed by matter, with each chemical element producing a unique spectral signature comparable to a fingerprint.
When light from a star passes through a planet's atmosphere or clouds of debris, certain elements absorb specific wavelengths, creating dark lines in the light spectrum. Studying these absorption lines allows scientists to precisely identify which elements are present and in what quantities.
In the case of white dwarfs, spectroscopy reveals elements that are depositing onto their surface from their environment. Since heavy elements should quickly sink toward the star's core under the effect of intense gravity, their detection on the surface indicates a recent supply of external matter.
This technique has enabled the discovery that LSPM J0207+3331 is accumulating elements from a planetary object being destroyed, thus providing direct evidence of accretion processes occurring in aging stellar systems.