Dark matter lampshades dimming stars could solve a major scientific mystery

Dark matter might act as 'lampshades', dimming stars, unlocking cosmic mysteries.

: Researchers suggest dark matter might form 'lampshades' that dim stars by drifting in front of them. These dark matter clumps, known as massive astrophysical compact halo objects (MACHOs), interact weakly with light, making stars appear temporarily dimmer. The effect could reveal the composition of dark matter, thought to be 85% of the universe's matter, remaining a major enigma. This technique to detect dimming, using data from surveys, can enhance the understanding of MACHOs and dark matter properties.

Astronomers are investigating whether dark matter might occasionally dim the light from distant stars—not by gravitational lensing, but through a phenomenon likened to cosmic "lampshades." These hypothetical lampshades would be diffuse clouds of dark matter that partially absorb or scatter starlight when passing between the stars and Earth. Though dark matter typically does not interact with light, some models allow for very weak photon interactions that could cause this kind of effect.

A study led by physicist Melissa Diamond from Queen’s University proposes that these "lampshade" effects could be detected using existing data from microlensing surveys like OGLE or EROS-2. These surveys have traditionally searched for brightening caused by gravitational lensing, but could also be repurposed to look for characteristic dimming patterns. Unlike normal celestial bodies that block starlight completely, a dark matter cloud would dim the light in a semi-transparent way, resulting in a distinct signal.

The theoretical basis for this idea lies in models where dark matter consists of exotic particles such as millicharged particles or self-interacting dark matter. These particles might form clumps dense enough to interact faintly with light. Though each interaction would be minimal, the collective effect across a dense enough cloud could create measurable dimming over time as the cloud moves across a star’s line of sight.

This technique does not require building new telescopes or instruments. Instead, it involves reanalyzing decades of existing data with a new focus. If detected, such dimming events would be the first evidence of dark matter interacting with photons, offering a breakthrough in understanding its true nature. Even null results would help rule out certain particle physics models, sharpening the direction of future research.

The search for dark matter has long been focused on gravitational effects alone. This “lampshade” method opens a complementary path, potentially revealing how dark matter subtly influences the universe in ways we’ve never directly observed before.

Sources: Space.com, Universe Today, Queen’s University

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