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Planetary Accretion Is Less Frequent in Wide Binaries: Evidence from Metal-Enriched White Dwarfs in DESI DR1

Using DESI DR1 data, this study reveals that wide binary systems host significantly fewer metal-enriched white dwarfs than single stars, suggesting that stellar binarity either suppresses the initial formation of planetary reservoirs or accelerates the depletion of planetary material.

Original authors: Siyi Xu, Laura. K. Rogers, Joan Najita, Boris T. Gänsicke, Paula Izquierdo, Sergey E. Koposov, Christopher J. Manser, Andrew Swan, Sandford Nathan, Wang Wenting, J. Aguilar, S. Ahlen, C. Allende Priet

Published 2026-09-11✓ Author reviewed ⓘ

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CC BY 4.0

Original authors: Siyi Xu, Laura. K. Rogers, Joan Najita, Boris T. Gänsicke, Paula Izquierdo, Sergey E. Koposov, Christopher J. Manser, Andrew Swan, Sandford Nathan, Wang Wenting, J. Aguilar, S. Ahlen, C. Allende Prieto, D. Bianchi, D. Brooks, T. Claybaugh, A. de la Macorra, J. E. Forero-Romero, Satya Gontcho A Gontcho, G. Gutierrez, R. Joyce, M. Landriau, L. Le Guillou, A. Meisner, R. Miquel, W. J. Percival, F. Prada, I. Pérez-Ràfols, G. Rossi, E. Sanchez, D. Schlegel, J. Silber, G. Tarlé, B. A. Weaver, R. Zhou

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Stars are rarely lonely. In our galaxy, roughly half of all sun-like stars have a companion, orbiting each other in a cosmic dance of gravity. For decades, astronomers have wondered how this partnership affects the birth and life of planets. Does the presence of a second star crush the nursery where planets form, or does it merely nudge them into different orbits? To answer this, scientists look to the remnants of planetary systems: the white dwarfs. These are the dense, cooling cores left behind when stars like our Sun run out of fuel and die. If a white dwarf is found to be polluted with heavy elements like calcium or iron, it is a clear sign that it has recently swallowed rocky debris—leftover building blocks from a planetary system that survived the star's death. By studying these polluted stars, researchers can trace the history of the planets that once orbited them.

A team of astronomers has now used a massive new survey of the sky to investigate how binary stars influence this process. They focused on a specific group of white dwarfs: those that are cool and have atmospheres dominated by helium. In these stars, the chemical fingerprints of swallowed planets are easier to spot. The researchers turned to the Dark Energy Spectroscopic Instrument, or DESI, a powerful robotic telescope survey that has already captured detailed light spectra for millions of stars. From this vast dataset, they identified thousands of cool white dwarfs and separated them into two groups: those that are alone and those that are part of a wide binary system, where the companion star orbits at a distance of hundreds or even thousands of times the distance between the Earth and the Sun.

The results revealed a striking difference between the two groups. Among the single white dwarfs, about twenty percent showed signs of having recently accreted planetary material. However, among the white dwarfs in wide binary systems, this number dropped significantly to just under ten percent. This difference is not a small fluctuation; the statistical evidence is so strong that the researchers are confident the result is real and not a random coincidence. The finding suggests that having a distant stellar companion makes it less likely for a planetary system to survive and deliver debris to the dying star.

The team also looked closer at the spacing between the binary stars to see if distance mattered. They found a tentative trend where the suppression of planetary debris was even stronger in systems where the companion star was closer, specifically within a separation of about one thousand astronomical units. While the data for this specific trend is not yet definitive, it aligns with the idea that the gravitational influence of a companion star might disrupt the formation of planets or clear them out more quickly than in single-star systems.

Two main possibilities explain why binary systems seem to have fewer surviving planetary remnants. The first is that these systems simply started with less material to begin with. The gravitational tug of a companion star during the early stages of a star's life might have prevented planetesimals—the rocky seeds of planets—from forming in large numbers. The second possibility is that the planetary systems formed normally but were destroyed more rapidly. The companion star could have stirred up the orbits of the remaining asteroids and comets, causing them to crash into the white dwarf sooner rather than later, leaving the older, cooler white dwarfs with nothing left to eat. The data currently cannot distinguish between these two scenarios, but it clearly establishes that stellar companionship plays a major role in the long-term fate of planetary systems.

This study also checked its findings against a separate, older survey of the sky to ensure the results were not an artifact of the new instrument. The older data showed the same pattern: binary systems had fewer polluted white dwarfs than single ones. Furthermore, the researchers confirmed that the white dwarfs in their binary sample were physically similar to the single ones in terms of temperature and brightness, ruling out the idea that the difference was caused by the stars simply looking different or being harder to see. The only major difference was their family structure.

The implications reach beyond just counting stars. If binary companions can strip away a star's planetary system, it changes our understanding of where planets can exist and how long they last. It suggests that while planets can form around binary stars, the environment is more hostile, leading to a quicker depletion of the rocky material that makes up these worlds. As astronomers continue to map the galaxy, these findings provide a crucial piece of the puzzle, showing that the presence of a second sun does more than just share the night sky; it fundamentally alters the history of the worlds that orbit the first.

Technical Summary: Planetary Accretion Is Less Frequent in Wide Binaries: Evidence from Metal-Enriched White Dwarfs in DESI DR1

Problem Statement
Binary stars are ubiquitous in the Galaxy, with binary fractions reaching approximately 50% for solar-type stars and higher for massive stars. A central question in astrophysics is how stellar multiplicity influences the formation and long-term evolution of planetary systems. While theoretical models suggest companions can truncate protoplanetary disks and inhibit giant planet formation, observational constraints on planetary systems in wide binaries remain limited. Previous studies utilizing metal-enriched white dwarfs (WDs) as tracers of remnant planetary systems have been hindered by small sample sizes (on the order of a few dozen), preventing robust statistical conclusions regarding the impact of wide binarity on planetary accretion.

Methodology
This study leverages the large, homogeneous spectroscopic catalog of white dwarfs from the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 (DR1), which contains 44,409 white dwarfs. The authors focus specifically on cool ( $T_{\text{eff}} < 11,500$ K), helium-dominated white dwarfs, where metal absorption lines are strongest and most detectable in low-resolution spectra.

The sample selection involved stringent quality cuts applied to the DESI DR1 catalog to ensure uniform data quality and reliable spectral classification:

Probability of being a white dwarf ( $P_{\text{WD}}$ ) $\ge 0.5$ .
Spectral type classification confidence $\ge 0.8$ .
Fiber contamination from field stars $\le 0.001$ (ensuring >99.9% of light originates from the WD).
Signal-to-noise ratio in the blue arm ( $SN_{\text{measured B}}$ ) $\ge 4$ to ensure sufficient detection of Ca H & K lines.
Observation in primary dark or bright survey programs.

These criteria reduced the sample to 32,456 high-quality WDs. The authors further filtered for cool helium-dominated WDs ( $5,000 \lesssim T_{\text{eff}} \lesssim 11,500$ K), resulting in a final sample of 2,805 objects.

To identify wide binaries, this sample was cross-matched with the Gaia eDR3 wide binary catalog (El-Badry et al. 2021). Systems were selected based on small probability of chance alignment ( $R_{\text{chance align}} < 0.01$ ) and exclusion of objects with high Gaia RUWE values ( $>1.25$ ) to remove close companions. This yielded 215 wide binary systems. A control sample of 2,578 single systems was constructed by excluding the identified binaries and high-RUWE objects from the initial 2,805.

Metal enrichment was identified by spectral classification: objects classified as DZ, DQZ, or DZQ (showing metal absorption lines) were considered enriched, while DC and DQ objects were considered non-enriched. The metal enrichment fraction ( $f$ ) was calculated for both samples using Poisson statistics.

Key Results

Enrichment Fraction Discrepancy: The study finds a significantly lower fraction of metal-enriched white dwarfs in wide binaries compared to single systems. The enrichment fraction for wide binaries is $9.8 \pm 2.1\%$ , whereas for single systems, it is $20.5 \pm 0.9\%$ . This difference represents a $4.7\sigma$ statistical significance.
Robustness: The result remains robust even when relaxing the chance alignment constraint ( $R_{\text{chance align}}$ up to 0.1), where the binary enrichment fraction remains $4.6\sigma$ lower than the single-star rate.
Sub-sample Analysis: Within the wide binary sample, white dwarf–white dwarf pairs show an enrichment fraction of $6.6 \pm 4.7\%$ , slightly lower than the $10.3 \pm 2.4\%$ found in white dwarf–main sequence binaries, though the sample size for the former is too small for definitive statistical comparison.
Separation Dependence: A tentative dependence on projected separation is observed. Systems with separations $< 1,000$ AU show an enrichment fraction of $4.9 \pm 2.5\%$ , while those between 1,000 and 10,000 AU show $12.4 \pm 3.2\%$ . While this trend is only at the $1.8\sigma$ level, it aligns with previous findings of suppressed accretion at smaller separations.
System Properties: Kolmogorov-Smirnov (KS) tests indicate that metal-enriched and non-enriched wide binary systems are statistically indistinguishable in terms of white dwarf temperature, surface gravity, signal-to-noise ratio, and companion color. Similarly, the wide binary and single-star samples are indistinguishable in these parameters, confirming that the difference in enrichment rates is not driven by selection biases in physical properties.
Validation: The single-system enrichment fraction ( $20.5 \pm 0.9\%$ ) is consistent with previous DESI Early Data Release (EDR) results ( $21 \pm 3\%$ ). Furthermore, a comparison sample from the Sloan Digital Sky Survey (SDSS) of cool helium-dominated WDs yields a similar trend ( $9.1 \pm 2.5\%$ for binaries vs. $22.9 \pm 0.8\%$ for singles), validating the DESI findings.

Significance and Claims
The paper claims that the significantly lower metal enrichment fraction in wide binaries compared to single stars provides strong evidence that binary systems either:

Start with a smaller initial reservoir of planetary material (due to suppressed planetesimal formation in binary environments), or
Deplete their planetary material more rapidly during the white dwarf stage.

The authors note that while theoretical models often suggest binaries enhance material delivery via mechanisms like the von Zeipel-Kozai-Lidov effect, this enhancement may occur earlier in the white dwarf's evolution (in hotter, younger WDs). The current study focuses on cool, old white dwarfs, where the lack of remaining unstable planetesimals suggests the reservoir has already been depleted or was never as large as in single systems.

The study concludes that stellar binarity plays a critical role in shaping the long-term evolution and survival of planetary systems. The authors emphasize that distinguishing between the "small reservoir" and "rapid depletion" hypotheses requires future modeling of individual systems to determine the magnitude and age dependence of metal enrichment, particularly by extending these analyses to warmer white dwarfs where the enrichment fraction in binaries appears comparable to single stars.

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