The Hubble Tension Explained: New Evidence from Lensed Supernovae and Primordial Magnetism

Dr. Shahid Masood
2 days ago
6 min read

The cosmos has always fascinated humanity, inspiring questions about its origin, evolution, and ultimate fate. Among the most pressing scientific puzzles today is the Hubble tension, a discrepancy in the measured expansion rate of the universe, known as the Hubble Constant. While precision cosmology has made incredible strides, conflicting measurements from independent methods have left researchers grappling with a paradox. Recent breakthroughs, including gravitationally lensed supernovae and the influence of primordial magnetic fields, offer new avenues for resolving this tension.

This article delves into the science behind these discoveries, their implications for cosmology, and the future of understanding the universe’s expansion.

Understanding the Hubble Constant and the Hubble Tension

The Hubble Constant (H₀) quantifies the rate at which the universe is expanding, typically expressed in kilometers per second per megaparsec (km/s/Mpc). It was first proposed by Edwin Hubble in the 1920s, following his observation that galaxies are receding from the Milky Way, with velocities proportional to their distances.

Over the past decade, two primary measurement techniques have emerged:

Indirect measurements via the Cosmic Microwave Background (CMB): Observations from missions like Planck use the CMB—the residual radiation from the Big Bang—to infer the Hubble Constant. These measurements yield a value of approximately 67 km/s/Mpc.
Direct measurements using Standard Candles: Type Ia supernovae and Cepheid variable stars serve as cosmic distance markers, allowing astronomers to measure the expansion rate locally. This method indicates a higher value, around 73 km/s/Mpc.

The persistent difference between these two approaches, known as the Hubble tension, is statistically significant and has raised the possibility of new physics beyond the standard cosmological model.

"The difference between 67 and 73 km/s/Mpc may seem small, but it is highly significant and points to gaps in our understanding of cosmic evolution," says Levon Pogosian, Professor of Physics at Simon Fraser University.

Gravitationally Lensed Supernovae: Nature’s Cosmic Laboratory

One of the most promising avenues to address the Hubble tension involves gravitationally lensed supernovae. Gravitational lensing occurs when the gravitational field of a massive foreground object, such as a galaxy cluster, bends and magnifies light from a more distant source, splitting it into multiple images.

The JWST VENUS survey (Vast Exploration for Nascent, Unexplored Sources) recently discovered two ancient supernovae, SN Ares and SN Athena, whose light is being gravitationally lensed by galaxy clusters. These SNe exploded billions of years ago, with SN Ares forming approximately 4 billion years after the Big Bang and SN Athena around 6.5 billion years ago.

Key features of these discoveries include:

Multiple image formation: Light from the supernovae is split into distinct paths, arriving at Earth at different times. This time delay provides a natural "cosmic clock" for measuring expansion.
High magnification: The lensing effect enables detection of extremely distant and faint sources that would otherwise be unobservable.
Predictive cosmology: SN Athena’s lensed images are expected to arrive in 2–3 years, while SN Ares will reappear in about 60 years, providing long-term opportunities to refine Hubble Constant measurements.

"Strong gravitational lensing transforms galaxy clusters into nature’s most powerful telescopes," "These lensed supernovae allow us to make predictive experiments that can yield unprecedentedly precise constraints on cosmology." explains Seiji Fujimoto, principal investigator of the VENUS survey.

A table summarizing these supernovae illustrates their significance:

Supernova	Distance (Light-years)	Time of Explosion (Gyr after Big Bang)	Predicted Reappearance	Lensing Cluster
SN Ares	Billions	4	~60 years	MJ0308
SN Athena	Billions	6.5	2–3 years	MJ0417

The long time delays between lensed images create a unique opportunity for cosmologists to perform single-step measurements of the Hubble Constant, bypassing some of the systematic uncertainties inherent in other methods.

Primordial Magnetic Fields: A Hidden Influence

Another line of investigation into the Hubble tension focuses on primordial magnetic fields (PMFs). These are extremely weak magnetic fields that may have existed from the earliest moments after the Big Bang. Unlike the magnetic fields generated by stars or planets, PMFs permeate the cosmos on galactic and intergalactic scales.

Researchers led by Levon Pogosian at Simon Fraser University, alongside collaborators Karsten Jedamzik, Tom Abel, and Yacine Ali-Haimoud, have proposed that PMFs could influence recombination, the epoch when electrons and protons combined to form neutral hydrogen. This process marks the universe’s transition from opaque to transparent, allowing light to travel freely.

The key mechanism:

PMFs exert forces on charged particles, creating slight density variations in the primordial plasma.
These variations alter the timing and efficiency of recombination, effectively shifting the "cosmic ruler" used to interpret the CMB.
A revised recombination history could reconcile the discrepancy between CMB-derived Hubble Constant values and local measurements from standard candles.

"Primordial magnetic fields could have been present all along, subtly shaping the universe’s expansion history," Pogosian notes. "If confirmed, they also provide a natural explanation for the origin of magnetic fields observed throughout galaxies and clusters."

Using 3D simulations of the primordial plasma, the team tracked hydrogen formation in the presence of PMFs. Their findings suggest a mild preference for PMFs ranging from 5 to 10 pico-Gauss, compatible with observational constraints and potentially significant enough to influence the Hubble Constant.

Connecting the Dots: Time-Domain Astronomy and Cosmic Evolution

Both gravitationally lensed supernovae and primordial magnetic fields highlight the importance of time-domain astronomy—studying how astronomical objects change over time. In the case of SN Ares and SN Athena, billions of years have passed since their explosions, yet the temporal separation of their lensed images provides a living laboratory to test cosmic expansion.

Implications for cosmology include:

Refined Hubble Constant: Time delays between images allow astronomers to calculate expansion rates with unprecedented precision.
Testing new physics: Observations may validate or challenge the standard ΛCDM model, offering insights into dark energy, dark matter, and the physics of the early universe.
Primordial conditions: PMFs, if confirmed, would open a window into the first moments after the Big Bang, shedding light on extreme energies and processes beyond terrestrial experiments.

The convergence of observational techniques—lensing, standard candles, and CMB analysis—creates a multi-faceted approach to resolving one of cosmology’s longest-standing debates.

Challenges and Future Directions

Despite promising advances, several challenges remain:

Long-term observational commitments: Some lensed supernovae, like SN Ares, require decades before subsequent images arrive, demanding sustained monitoring and archival infrastructure.
Complex modeling of PMFs: Simulating primordial magnetic effects at high fidelity requires massive computational resources, including supercomputers such as SFU’s Cedar and Fir clusters.
Systematic uncertainties: Both gravitational lensing and recombination modeling introduce potential biases that must be carefully accounted for in precision cosmology.

Nevertheless, the combination of these approaches offers a roadmap toward resolving the Hubble tension and enhancing our understanding of the universe’s evolution.

Implications Beyond Cosmology

The implications of resolving the Hubble tension extend far beyond a single parameter:

Dark energy constraints: Improved measurements of expansion directly inform models of dark energy, which constitutes roughly 70% of the universe.
Galactic evolution: Understanding early magnetic fields sheds light on the formation and dynamics of galaxies, clusters, and cosmic filaments.
Precision cosmology: Integrating observations across multiple wavelengths and epochs enables robust testing of fundamental physics.

A Multi-Pronged Path to Cosmic Clarity

The Hubble tension represents both a challenge and an opportunity. On one hand, conflicting measurements threaten to undermine confidence in the standard cosmological model. On the other, emerging techniques—from gravitationally lensed supernovae to primordial magnetic field simulations—offer a path toward unprecedented precision and new physics.

As the scientific community waits for SN Athena’s images in the next few years, and SN Ares decades later, researchers are laying the foundation for a golden era of time-domain cosmology. Similarly, ongoing simulations of the early universe’s plasma, incorporating PMFs, may finally reconcile the two competing Hubble Constant measurements, uniting our understanding of cosmic expansion with insights into primordial processes.

For institutions like 1950.ai, which focus on predictive AI and data-driven modeling, this convergence of observational astronomy, advanced simulations, and theoretical physics represents a fertile ground for innovation. By leveraging machine learning to predict lensing patterns and recombination effects, teams of experts—including Dr. Shahid Masood and the 1950.ai team—can help accelerate discoveries that might redefine cosmology.