Probing the Solar System for Scalar Dark Matter ✛ ✦
Context
Dark matter makes up about 27% of the universe's energy, but its nature remains unknown. Observations by Vera Rubin and others showed that galaxies rotate too fast for the visible matter. Among the candidates are ultralight scalar fields with masses of $10^{-22}$–$10^{-10}$ eV, which can form coherent oscillations or compact self-gravitating clumps (such as axion-like boson stars). Studying these objects with Solar System methods opens a unique window into dark matter physics, complementing existing astrophysical and laboratory searches.
Methods
A simple analytical framework is developed for each channel. For flares from dark matter clumps colliding with Kuiper Belt bodies, which can generate flares via the advection-dominated accretion (ADAF) mechanism, the collision rate with a population of ~$10^5$ objects is estimated using the geometric cross-section and the local dark halo density. The peak luminosity is estimated from the gravitational interaction energy, and the detectability radius through the sensitivity of surveys like LSST. For atomic clocks, a model is constructed linking the modulation of frequency ratios to the oscillation amplitude of fundamental constants (fine-structure constant etc.), predicted within the Klein–Gordon equation for a non-relativistic field; sensitivity depends on the difference of sensitivity coefficients $K_X$. The possibility of varying constants was already pointed out by Paul Dirac. In the astrometric microlensing channel, an idea developed by Fritz Zwicky, the standard formalism of centroid shift when a compact lens passes near the line of sight is used, and the event rate is derived from the number of stars, transverse velocity, and line-of-sight integral.
Results
For the flare channel, a rate $Γ_{trig}$ ~ $10^{-4}$ ($f_s$/$10^{-2}$)($M_s$/$10^{-10}$ M_⊙)^{-1/3} events per year is obtained. Over a decade-long survey monitoring $10^5$ Kuiper Belt objects, the absence of a signal imposes a limit $f_s$ < 5×$10^{-3}$ ($M_s$/$10^{-10}$ M_⊙)^{1/3} at 95% confidence level. The peak luminosity reaches ~$10^{22}$ W for a clump mass of $10^{-10}$ M_⊙, which is comparable to the X-ray emission of a young neutron star and accessible to the Vera Rubin telescope. For atomic clocks, a relation between the modulation amplitude $A_{ij}$ and the effective coupling constant $d_{eff}$ is derived: $A_{ij}$ ∝ $d_{eff}$ m_φ^{-1}. With clock precision of $10^{-18}$, it is possible to constrain |$d_X$| at a level depending on the field mass. For astrometric lensing, the minimum detectable mass $M_{min}$ ≈ $10^{-2}$ ($σ_{th}$/100 μas) M_⊙ for Galactic lenses, while local clumps at a distance of 100 AU are detectable down to masses of $10^{-11}$ M_⊙ with 10 μas precision. The limit on the clump fraction at high masses plateaus: $f_s$ ≲ 7×$10^{-3}$ ($σ_{th}$/100 μas) for a survey with $10^8$ stars over 5 years. Future astrometry (10–30 μas) will enable reaching $f_s$ ~ $10^{-3}$–$10^{-2}$ for masses up to $10^{-4}$ M_⊙.
Implications
The proposed methods collectively cover different manifestations of the scalar dark sector: flares are sensitive to compact clumps with non-zero interaction with ordinary matter, clocks to the coherently oscillating component, and lensing exclusively to the gravity of clumps. This enables multi-channel checks and cross-confirmation of signals. Moreover, the results link local observations in the Solar System to the physics of ultralight scalars, expanding the search program beyond traditional cosmological and direct detectors.
Future development
With the advent of new surveys (LSST, Roman) and improved precision of atomic clocks (down to $10^{-19}$ and below) and astrometry (missions like GaiaNIR), sensitivity will increase by orders of magnitude. It will become possible to probe parameter regions where scalar dark matter could explain the missing substructure in halos or the 'cuspy' problem. The three-channel analysis will become a standard tool for data interpretation.
Impact
The results will impact particle astrophysics, cosmology, and fundamental physics by providing new constraints on axion-like particles and ultralight scalar models, as well as stimulating the development of precision astrometry and atomic clock networks.
Next steps
Next steps include analyzing real Gaia data to search for astrometric events, conducting dedicated monitoring campaigns of the Kuiper Belt for flares, and organizing global coordinated observations of atomic clocks with maximum sensitivity.
Key open problems
The work touches on the problem of the nature of dark matter, the mass hierarchy and gauge hierarchy problem through ultralight scalars, as well as the question of the stability of fundamental constants over time.
The knowledge machine's view
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
This work explores three channels for probing scalar dark matter in the Solar System: flashes from clump collisions with Kuiper Belt objects, atomic clock modulation, and astrometric microlensing. For each channel, analytical estimates of event rates and constraints on dark matter parameters are derived, with lensing using Gaia data emerging as the most promising.
Where its strength is
The strength of the work lies in combining three independent methods into a unified picture and identifying astrometric lensing as the most mature channel, capable of providing constraints already now, without waiting for future instruments.
Where it could go next
- It might be interesting to see how radio searches for axion-like particles via resonant cavities complement astrometric constraints. In our archive, there is a nearby work showing how dark matter could manifest in the radio band through conversion into photons.based on: Dark Matter Speaks in Radio Waves arXiv:2605.05906
- The idea of using the Earth as a detector for charged dark matter relics, discussed in a neighboring article, could suggest how to combine direct searches in matter with astrometric methods for scalar fields.based on: Earth as a Dark Matter Detector: Hunting Charged Relics arXiv:2607.09845
Worth trying
- Investigate whether Gaia data can be used not only for lensing but also for searching for periodic stellar shifts caused by an oscillating scalar field background.
- Assess how radio astronomy constraints on axion-photon conversion compete with astrometric constraints in the same mass range.
- Consider a combined analysis: searching for clumps simultaneously in astrometry and in gamma-ray bursts from annihilation in the solar corona, as proposed in the work on gamma-ray glow around the Sun.
Nearby works in our archive
- Earth's Shadow Hunts for Alien Probessimilarity 0.69
- Dark Matter Speaks in Gamma-Ray Lightsimilarity 0.68
- Dark Matter Ignites a Gamma Glow Around the Sunsimilarity 0.68
- Mysterious Dark Object Challenges Theoriessimilarity 0.67
- Dark Matter Speaks in Radio Wavessimilarity 0.67
- Earth as a Dark Matter Detector: Hunting Charged Relicssimilarity 0.67
The closest work in the archive sits at 0.69 by meaning — the usual level for our corpus.
Original abstract
as written by the authors arXiv:2607.12144
Scalar field dark matter provides us with a well motivated alternative to conventional particle dark matter, especially when ultralight fields form coherent oscillations or compact self gravitating clumps. Here we develop three complementary Solar System and local Galactic level probes of such models. These probes pertain to ADAF-like flares from scalar clump encounters with Kuiper Belt Objects, atomic clock searches for oscillatory variations of fundamental constants and astrometric microlensing by compact scalar clumps. We derive simple sensitivity estimates and null detection bounds on the scalar clump fraction, clock couplings and compact lens abundance. Our results show that Gaia-like astrometry can probe compact scalar clumps at the percent level near $$M_s\gtrsim10^{-2}M_\odot$$, while future astrometric and clock experiments can extend the reach to lower masses and weaker couplings.
The mass of an ultralight scalar field could be $10^{-22}$ eV — 28 orders of magnitude less than the electron mass. Such particles behave as quantum waves with a de Broglie wavelength of thousands of light-years, forming 'fuzzy' dark matter halos.
Key numbers
- flare rate: 10⁻⁴ events per year (for f_s=0.01, M_s=10⁻¹⁰ M_⊙)
- peak luminosity: 10²² W
- minimum mass of a Galactic lens: ~10⁻² M_⊙ (at 100 μas precision)
- local dark matter density: 0.4 GeV/cm³
- transverse velocity of clumps: ~200 km/s