The latest Hubble Space Telescope observations reveal a twist in the story of Uranus’s moons. Rather than the expected radiation “sunburn,” the moons Ariel, Umbriel, Titania and Oberon seem to be literally gathering cosmic dust. It turns out the planet’s odd tilt isn’t scorching their backsides as predicted, but coating the front ends of the two outer moons in a kind of space-grime instead. This result has astronomers scratching their heads, because it’s just the opposite of what they expected under Uranus’s warped magnetic field.

Dust, Not Radiation

According to the data from NASA’s Voyager 2 flyby in 1986 and decades of modelling, scientists assumed Uranus’s sideways spin meant its magnetic field blasted each moon’s trailing side (the “back window”) with charged particles, darkening it. The rear halves were expected to look dull and dark. Instead, Hubble’s ultraviolet data tell a different story: Titania and Oberon (the distant pair) are actually darker on their leading faces – the opposite of what that radiation hypothesis predicted. In other words, the effect isn’t radiation damage at all. Instead, it looks like Uranus’s magnetosphere largely misses these moons.

A Cosmic Windshield Effect

Space dust kicked up by Uranus’s far-flung irregular moons. Micrometeorites constantly pummel those distant satellites, flinging tiny grit inward over millions of years. Titania and Oberon plow through this dust cloud, collecting debris on their forward sides just like bugs on a car’s windshield. This cosmic “bug splatter” coats their leading faces with a slightly darker, reddish tint.

Meanwhile, Ariel and Umbriel ride in the dust shadows of their bigger siblings and look about the same brightness on both sides. Uranus’s big moons have gone through a slow-motion cosmic car wash, dusting their fronts instead of catching a UV burn. In other words, a dusty windshield — not radiation — is painting these moons. It’s a reminder that space can surprise us, sometimes with nothing more exotic than plain old dust.

A recent effort to do away with singularities — the infinitely dense points believed to be at the heart of black holes — has reignited debate among physicists. Now, a team led by Robie Hennigar of Durham University suggests a new model that has gravity undergoing a different type of behaviour at the extreme limits and replaces the singularity of the black hole with a small, compact core that always remains static and very strongly curved. The modified Einstein’s equations, representing general relativity, have been generalised, and higher-dimensional effects are incorporated. Although the discoveries garnered attention for perhaps explaining a fundamental cosmic paradox, critics have mentioned that the model has no experimental underpinning and is based on overly speculative mathematical concepts.

Critics Challenge 5D Gravity Theory Aimed at Replacing Black Hole Singularities Without Evidence

As per a Space.com report, Hennigar’s theory introduces modified gravity in five dimensions, which some scientists argue goes beyond what current observations allow. Nikodem Poplawski, a physicist at the University of New Haven in Connecticut, pointed out three things that stood out to him: there is no experimental evidence for extra dimensions, the current study only assumes a static black hole interior, and the model uses an infinite series of mathematical terms that don’t have any physical justification.

Poplawski stressed that changing general relativity without experimental evidence makes the model more of a theoretical curiosity than a real physical theory. He also highlighted the fact that black hole interiors, according to conventional field equations, should not be static. He further stated that just changing equations to get rid of singularities doesn’t fix the physics behind them; it can only hide it behind complicated mathematics.

Hennigar’s team used modified gravity to deal with the singularity, but scientists say that general relativity and quantum mechanics should be combined. The problems with string theory, however, include features such as dimensions that have never been fixed and supersymmetric particles that have never been detected.

Poplawski concurs that investigating mathematics may be fruitful and also hopes that bold ideas, such as the notion that black holes spawn new universes, may prove profitable in the future.