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One of the biggest mysteries in astrophysics may be getting closer to an answer.

A new study published in Physical Review Letters suggests that the famous “Amaterasu particle” — one of the most energetic cosmic rays ever detected — may not have been a proton at all. Instead, it could have been an atomic nucleus heavier than iron.

Discovered in 2021 by the Telescope Array in Utah, the Amaterasu particle carried an astonishing 240 exa-electron volts (EeV) of energy. That’s roughly the same kinetic energy as a fast-moving tennis ball — compressed into a single atomic nucleus.

What puzzled scientists most was its apparent origin. The particle seemed to arrive from a vast cosmic void, a region of space with no obvious object capable of accelerating particles to such extreme energies.

Using detailed simulations, researchers found that ultraheavy nuclei may survive intergalactic journeys far better than protons. While lighter particles lose energy through interactions with background radiation, nuclei heavier than iron can retain much more of their original energy over cosmic distances.

If correct, the finding could help explain how particles like Amaterasu reach Earth from seemingly impossible locations.

Possible sources include:
• Collapsing massive stars
• Neutron star mergers
• Gamma-ray bursts

Future instruments such as AugerPrime and the proposed Global Cosmic Ray Observatory may reveal whether these ultraheavy nuclei are truly responsible for some of the most extreme particles ever observed.

Every ultrahigh-energy cosmic ray is a messenger from one of the universe’s most violent events. Understanding what these particles are made of may help us uncover where they come from — and how nature accelerates matter to energies far beyond anything humans can create.

What do you think is the most likely source of particles this extreme?

📄 Original paper · ScienceDaily summary

#CosmicRays #Astrophysics #ParticlePhysics #SpaceScience #NeutronStars

🌌 Dark Energy Survives Its Latest Crisis

For a moment, cosmology had a real scare.

A 2025 study suggested that the universe’s accelerating expansion might be partly an illusion — not because dark energy disappeared, but because Type Ia supernovae, the “standard candles” used to measure cosmic distances, may change their brightness depending on the age of the stars that produce them.

If that were true, one of modern cosmology’s biggest discoveries would need a serious rethink.

Now, an international team including Nobel laureates Adam Riess and Brian Schmidt has pushed back hard. In a new paper in Monthly Notices of the Royal Astronomical Society, led by Dr. Phil Wiseman of the University of Southampton, the researchers argue that the evidence for cosmic acceleration remains robust.

The problem, they say, was not dark energy — it was the correction.

The 2025 analysis made two major mistakes. First, it treated the age of a host galaxy as if it were the age of the specific star system that later exploded as a supernova, exaggerating the age difference between nearby and distant supernovae by a factor of three to five. Second, it left out a standard correction for the mass of the host galaxy — something modern supernova cosmology already uses because galaxy environments affect observed brightness.

Once those effects are included, the dramatic claim largely disappears.

• The claimed ~5-billion-year age gap between nearby and distant supernovae was overstated
• After standard corrections, there is no significant brightness difference between young and old supernova environments
• Data from the Dark Energy Survey show no meaningful evolution of the host-mass effect
• Including the proposed bias shifts the dark-energy equation-of-state parameter by less than 0.01

That does not mean we understand dark energy. We still don’t.

It makes up roughly 68% of the universe’s mass-energy budget, yet we have no clear physical explanation for what it actually is. A cosmological constant? Vacuum energy? Something that changes over time? A sign that gravity itself is incomplete on cosmic scales?

The new result does not solve the mystery. It simply says the original signal — the accelerating expansion of the universe — is still standing.

And that matters. Because the next generation of sky surveys, including the Vera C. Rubin Observatory’s 10-year Legacy Survey of Space and Time, is designed to measure exactly this kind of cosmic acceleration with far greater precision.

So the crisis may be averted.

But the real question remains: what kind of invisible “something” can dominate the universe — and still refuse to show itself directly?

https://doi.org/10.1093/mnras/stag797



#DarkEnergy #Cosmology #Astrophysics #Supernova #Physics #science

🔭 Astronomers Have Just Opened a New Map of the Black Hole Universe

The LIGO–Virgo–KAGRA collaboration has released GWTC-5.0 — the largest gravitational-wave catalog ever assembled.

It adds 161 new detections from the O4b observing run, bringing the total number of observed gravitational-wave events since 2015 to 390. What began as a handful of almost unbelievable signals has now become a real population study of black holes.

The jump is dramatic. The fourth observing run alone now accounts for roughly 75% of all gravitational-wave events detected so far. In LIGO’s first observing run, scientists detected just three events over about four months. Now the network is catching around 3–4 black hole mergers per week.

And the data are starting to reveal something deeper: black holes do not all form the same way.

Some likely come from pairs of massive stars born together. Others may meet later inside dense stellar clusters. The most intriguing group are “second-generation” black holes — objects that were themselves created in earlier black hole mergers, then merged again. Their clue is unusually rapid spin, which can act like a fingerprint of these repeated cosmic collisions.

A few highlights from the new catalog:

— 390 gravitational-wave events in total
— 161 new detections from O4b
— Black hole masses clustering around ~10 and ~35 solar masses
— Evidence for second-generation black holes from hierarchical mergers
— Best sky localization yet: one event narrowed down to just 6 square degrees
— Clearest black hole signal ever recorded, with a signal-to-noise ratio of 76.9
— A new gravitational-wave measurement of the Hubble constant with ~25% improved precision

Why it matters: gravitational-wave astronomy is no longer just about detecting rare cosmic “chirps.” It is becoming a census of an invisible universe — one that can study black hole populations, test general relativity, probe stellar evolution, and even help measure the expansion rate of the cosmos.

The big takeaway: astronomy no longer needs light alone. We are now listening to spacetime itself — and the signal is turning into a map.

📄 LIGO press release: https://www.ligo.caltech.edu/news/ligo20260526
📖 Summary: https://www.sciencealert.com/lost-world-of-gravitational-waves-reveals-the-origins-of-black-holes

#GravitationalWaves #BlackHoles #LIGO #Astrophysics #Cosmology

🔭 NASA Discovers a “Wandering” Supermassive Black Hole Devouring a Star Far from Any Galactic Center

Astronomers have observed something never before seen in optical light: a supermassive black hole tearing apart a star more than 30,000 light-years from the center of its host galaxy — far from where such giants are normally found.

The event, designated TDE 2025abcr, was first detected in November 2025 by the Zwicky Transient Facility. An AI algorithm scanning roughly 500,000 transient events every night flagged an unusual flare despite its highly unexpected location in the outskirts of a galaxy.

At its peak, the flare shone with the luminosity of roughly 10 billion Suns, briefly outshining its host galaxy in ultraviolet light. Follow-up observations with NASA’s Neil Gehrels Swift Observatory showed that the culprit is a black hole with a mass of about one million Suns, feeding on a star that wandered too close.

So how did such a massive black hole end up so far from the galactic center?

Astronomers propose two leading explanations:

• it was gravitationally ejected during a past merger involving multiple supermassive black holes;

• or it originally belonged to a dwarf galaxy that is still merging with the larger host galaxy.

The discovery demonstrates a new way to find these otherwise invisible wandering supermassive black holes. With the Vera C. Rubin Observatory beginning operations and NASA’s Nancy Grace Roman Space Telescope on the horizon, astronomers expect to uncover many more—revealing how common these cosmic wanderers really are and providing new clues about the violent merger history of galaxies.

Sources:

NASA: https://science.nasa.gov/missions/swift/nasas-swift-sees-wandering-mega-black-hole-shredding-star/

The Astrophysical Journal Letters: https://iopscience.iop.org/article/10.3847/2041-8213/ae77f3

#Astronomy #BlackHoles #NASA #Astrophysics #SpaceScience