A massive galaxy with no dark matter?

A Telescope’s Quest to Unravel Dark Matter Decay

Unraveling Mysteries with Hydrogen Emission!


Hydrogen is not just the universe’s most prolific element – it’s a window into the cosmos’s profound mysteries. Accounting for over 90% of universal atoms, hydrogen’s sheer quantity surpasses helium atoms by tenfold and dwarfs all other elemental atoms by a factor of a hundred. This omnipresent element manifests itself everywhere, from our vast oceans to the universe’s primordial territories. This ubiquity is a boon for astronomers because neutral hydrogen radiates a subtle emission line of radio light, commonly recognized as the H I hydrogen or 21-centimeter line.

Hydrogen’s structure, one electron tethered to a singular proton, can exhibit two alignment styles. One, where the spins match, represents a marginally heightened energy state compared to their opposite alignment. This difference allows electrons to flip their spin, emitting a photon in the process. Notably, hydrogen achieves this without any need for extreme temperatures or ionization, ensuring a consistent emission of 21-centimeter radio light across hydrogen-rich regions.

Hydrogen’s Cosmic Role in Understanding Dark Matter

The specificity of the emission line’s wavelength becomes a tool for deducing hydrogen’s relative motion and the cosmological redshift. One of its earliest applications was pivotal for Vera Rubin, as it illuminated the existence of dark matter by assessing hydrogen motion within the Milky Way and its galactic neighbors. Fast forward to the present, and researchers suggest this emission line might unlock the first concrete proof of dark matter particles.

Recent research, currently accessible on the pre-print platform arXiv, highlights the potential of the Hydrogen Epoch of Reionization Array (HERA). Stationed in South Africa, this radio telescope excels at peering into the universe’s youth, observing its early hydrogen.


Upon activation, HERA aims to chart hydrogen’s expansive structure during the universe’s darkest and earliest epochs – a span punctuated by the Big Bang’s residual luminance and the emergence of celestial bodies. This phase was dominated by the elusive dark matter, complemented by warm hydrogen gas clouds.

WIMPs: The Enigma within the Enigma

Should dark matter strictly adhere to a neutral stance, only influenced gravitationally by matter and light, the 21-centimeter emission remains the sole light source from this era. However, prevailing dark matter theories often spotlight Weakly Interacting Massive Particles (WIMPs).

These neutral dark matter entities outweigh conventional matter particles, such as protons and electrons. On rare occasions, WIMPs might disintegrate into regular matter, producing surges of electrons, positrons, protons, or anti-protons. These resultant particles, if present, would invariably interact with the 21-centimeter emission.

Our understanding, rooted in cosmic microwave background observations, alludes to WIMPs possessing an incredibly prolonged decay lifespan. The lack of observed dark matter decay implies the near-nonexistence of WIMPs or an inconceivably extensive half-life. Yet, this research indicates that even with a lifespan surpassing our current estimates by thousands, HERA could discern its impact on the early universe within a mere 1,000-hour observation window.


HERA’s observations, whether conclusive or not, promise monumental advances. Its capability to scrutinize dark matter’s longevity could potentially debunk some WIMP theories, refining our grasp on this cosmic mystery.

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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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