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Polarized blazar X-rays imply particle acceleration in shocks
Polarization measurements are reported for the blazar Mk501, revealing a degree of X-ray polarization that is more than twice the optical value and supporting the shock-accelerated energy-stratified electron population scenario.
- Ioannis Liodakis
- , Alan P. Marscher
- & Silvia Zane
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Article |
The diffuse γ-ray background is dominated by star-forming galaxies
The diffuse, isotropic background of gamma rays comes mainly from star-forming galaxies, according to a physical model of gamma-ray emission.
- Matt A. Roth
- , Mark R. Krumholz
- & Silvia Celli
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Article |
Ultrahigh-energy photons up to 1.4 petaelectronvolts from 12 γ-ray Galactic sources
Observations of γ-rays with energies up to 1.4 PeV find that 12 sources in the Galaxy are PeVatrons, one of which is the Crab Nebula.
- Zhen Cao
- , F. A. Aharonian
- & X. Zuo
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Article |
Detection of a particle shower at the Glashow resonance with IceCube
A particle shower detected by the IceCube Neutrino Observatory at the very high energy of the Glashow resonance demonstrates its potential for the study of high-energy particle physics and astrophysics.
- M. G. Aartsen
- , R. Abbasi
- & M. Zöcklein
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Article |
Probing the energetic particle environment near the Sun
The Parker Solar Probe mission has reached the inner heliosphere of the Sun and made measurements of energetic particle events in the near-Sun radiation environment.
- D. J. McComas
- , E. R. Christian
- & A. P. Rouillard
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Article |
A very-high-energy component deep in the γ-ray burst afterglow
Very-high-energy γ-rays observed ten hours after the prompt emission of the γ-ray burst 180720B can be attributed to either an inverse Compton or an extreme synchrotron process.
- H. Abdalla
- , R. Adam
- & O. J. Roberts
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Letter |
Observation of two-neutrino double electron capture in 124Xe with XENON1T
Two-neutrino double electron capture is observed experimentally in 124Xe with the XENON1T detector, yielding a half-life of 1.8 × 1022 years.
- E. Aprile
- , J. Aalbers
- & J. P. Zopounidis
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Letter |
An experiment to search for dark-matter interactions using sodium iodide detectors
Early results from the COSINE-100 experiment—designed to test a much-debated claim of the detection of a dark-matter signal—show no indications of dark matter, providing evidence against the previous claim.
- Govinda Adhikari
- , Pushparaj Adhikari
- & Seok Hyun Yong
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Article |
Comprehensive measurement of pp-chain solar neutrinos
All components of the proton–proton nuclear fusion chain, in which hydrogen is converted into helium in the Sun, are described, with several implications for fundamental solar and particle physics.
- M. Agostini
- , K. Altenmüller
- & G. Zuzel
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Letter |
Very-high-energy particle acceleration powered by the jets of the microquasar SS 433
Observations of teraelectronvolt γ-rays accelerated by the jets of the miniature quasar SS 433 are reported.
- A. U. Abeysekara
- , A. Albert
- & H. Zhou
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Letter |
Autogenous and efficient acceleration of energetic ions upstream of Earth’s bow shock
Observations of a hot flow anomaly accelerating solar-wind ions suggest a mechanism for such acceleration—a Fermi acceleration trap caused by Earth’s bow shock interacting with the solar wind.
- D. L. Turner
- , L. B. Wilson III
- & J. L. Burch
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Letter |
A small amount of mini-charged dark matter could cool the baryons in the early Universe
Calculations show that if some dark-matter particles—less than one per cent—have a tiny charge, their coupling to baryons could cool the baryons enough to explain puzzling astrophysical observations.
- Julian B. Muñoz
- & Abraham Loeb
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Letter |
Possible interaction between baryons and dark-matter particles revealed by the first stars
The large absorption of the 21-centimetre transition of hydrogen around redshift 20 is explained by radiation from the first stars, combined with excess cooling of the cosmic gas caused by baryon–dark matter scattering.
- Rennan Barkana
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Letter |
Direct detection of a break in the teraelectronvolt cosmic-ray spectrum of electrons and positrons
A direct measurement of cosmic-ray electrons and positrons with unprecedentedly high energy resolution reveals a spectral break at about 0.9 teraelectronvolts, confirming the evidence found by previous indirect measurements.
- G. Ambrosi
- , Q. An
- & S. Zimmer
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Letter |
Measurement of the multi-TeV neutrino interaction cross-section with IceCube using Earth absorption
IceCube has measured the absorption of atmospheric and astrophysical neutrinos in the Earth, and found that the interaction cross-section of multi-TeV neutrinos is within 50 per cent of the predictions of the standard model.
- M. G. Aartsen
- , M. Ackermann
- & M. Zoll
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Letter |
Significant and variable linear polarization during the prompt optical flash of GRB 160625B
The prompt optical flash produced by the γ-ray burst GRB 160625B is highly linearly polarized, suggesting that it is produced by fast-cooling synchrotron radiation in a large-scale magnetic field.
- E. Troja
- , V. M. Lipunov
- & N. Gehrels
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Letter |
Experimental signatures of the mixed axial–gravitational anomaly in the Weyl semimetal NbP
A positive magneto-thermoelectric conductance is observed in the Weyl semimetal niobium phosphide, suggesting the presence of the elusive mixed axial–gravitational anomaly.
- Johannes Gooth
- , Anna C. Niemann
- & Kornelius Nielsch
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Letter |
Recent near-Earth supernovae probed by global deposition of interstellar radioactive 60Fe
Analysis of deep-ocean archives reveals that a few per cent of fresh 60Fe has been captured in interstellar dust and deposited in Earth’s crust, indicating that many supernova events occurred over the past ten million years within a distance of up to 100 parsecs from Earth.
- A. Wallner
- , J. Feige
- & S. R. Winkler
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Letter |
Acceleration of petaelectronvolt protons in the Galactic Centre
Deep γ-ray observations of the Galactic Centre with arcminute angular resolution show traces of petaelectronvolt protons within the central ten parsecs of our Galaxy; the accelerator of these particles could have provided a substantial contribution to Galactic cosmic rays in the past.
- A. Abramowski
- , F. Aharonian
- & HESS Collaboration
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Letter |
A large light-mass component of cosmic rays at 1017–1017.5 electronvolts from radio observations
High-resolution radio measurements of air showers—cascades of secondary particles in the atmosphere initiated by cosmic rays—reveal that cosmic rays with energies of 1017–1017.5 electronvolts have a mixed composition, with light elements (protons and helium nuclei) making up 80 per cent of their mass.
- S. Buitink
- , A. Corstanje
- & J. A. Zensus
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Letter |
Measurement of interaction between antiprotons
The interaction between antiprotons, produced by colliding high-energy gold ions, is shown to be attractive, and two important parameters of this interaction are measured, namely the scattering length and the effective range.
- L. Adamczyk
- , J. K. Adkins
- & M. Zyzak
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Article |
Neutrinos from the primary proton–proton fusion process in the Sun
Spectral observations of the low-energy neutrinos produced by proton–proton fusion in the Sun demonstrate that about 99 per cent of the Sun’s power is generated by this process.
- G. Bellini
- , J. Benziger
- & G. Zuzel
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Letter |
Asymmetries in core-collapse supernovae from maps of radioactive 44Ti in Cassiopeia A
The observation of non-uniformly distributed titanium emission in the interior of Cassiopeia A, a core-collapse supernova, is an indicator of asymmetries in the stellar explosion and provides strong evidence for the development of low-mode convective instabilities in such supernovae.
- B. W. Grefenstette
- , F. A. Harrison
- & W. W. Zhang
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Review Article |
Cold dark matter heats up
In the ΛCDM paradigm, 95% of the Universe consists of dark energy and cold dark matter, but the low-density cores of dark matter measured at the centre of galaxies are hard to explain using this model; here a review of recent work shows that the action of stars and gas can significantly alter the distribution of cold dark matter through a coupling based on rapid gravitational potential fluctuations.
- Andrew Pontzen
- & Fabio Governato
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News |
IceCube catches high-energy neutrino oscillations
Astrophysical telescope finds secondary role as particle-physics experiment.
- Calla Cofield
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News |
Dark matter results spark debate
Competing experiments present a puzzling picture, as seen through Storify.
- Eugenie Samuel Reich
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News & Views |
Sterile neutrinos
An analysis of neutrino data suggests that there may be additional types of neutrinos beyond the three currently known. If confirmed, the existence of these additional particles could have an impact on astrophysics and cosmology.
- William C. Louis
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News Explainer |
Shedding light on the mystery of dark matter
New findings spotlight conflicting results from search for elusive theoretical particles.
- Ron Cowen
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News & Views |
A multi-messenger story
The IceCube detector is a super-sensitive tool with which astronomers hope to find the elusive neutrinos from cosmic γ-ray bursts. A search that, surprisingly, has come up empty handed prompts a rethink of the underlying theory.
- Dieter H. Hartmann
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Comment |
From isotopes to the stars
Creating more exotic isotopes will reveal the stellar formation of atoms — a fitting tribute to Ernest Rutherford, say Michael Thoennessen and Bradley Sherrill.
- Michael Thoennessen
- & Bradley Sherrill
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News |
Antiuniverse here we come
A controversial cosmic-ray detector destined for the International Space Station will soon get to prove its worth.
- Eugenie Samuel Reich
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Letter |
Observation of the antimatter helium-4 nucleus
- H. Agakishiev
- , M. M. Aggarwal
- & Y. Zoulkarneeva.
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News Feature |
Physics: Unification + 150
In 1861, James Clerk Maxwell unified electricity, magnetism and light. Experiments under way today could inch physicists closer to combining everything else.
- M. Mitchell Waldrop
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News |
Superfluid state for Galaxy's youngest neutron star?
A neutron star in Cassiopeia A could be cooling to form an exotic state of matter.
- Kate McAlpine
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Review Article |
The moment of truth for WIMP dark matter
We know that dark matter constitutes 85 per cent of all the matter in the Universe, but we do not know of what it is made. Among the many dark matter candidates proposed, WIMPs (weakly interacting massive particles) occupy a special place. The moment of truth has now come for WIMPs: either we will discover them in the next five to ten years, or we will witness their inevitable decline.
- Gianfranco Bertone
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Letter |
A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2
The peculiar object P/2010 A2, discovered in January 2010, is in an asteroidal orbit in the inner main asteroid belt and was given a cometary designation because of the presence of a trail of material. These authors report observations of P/2010 A2 by the Rosetta spacecraft. They conclude that the trail arose from a single event, an asteroid collision that occurred around 10 February 2009.
- Colin Snodgrass
- , Cecilia Tubiana
- & K.P. Wenzel
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Research Highlights |
Physics: Mini mass
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News |
Collider gets yet more exotic 'to-do' list
The Large Hadron Collider could throw up evidence of new physics earlier than expected.
- Zeeya Merali
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News |
Urgent refit for space magnet
Particle physicists in a race against time to overhaul US$1.5-billion cosmic-ray detector.
- Edwin Cartlidge
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News |
Hunt for the sterile neutrino heats up
The elusive particles, if they exist, could help solve some of the most pressing problems in astrophysics.
- Eric Hand
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News |
Are the Universe's secrets hiding on a chip?
Topological insulator could help to test quantum field theory.
- Geoff Brumfiel
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News & Views |
Gravity tested on cosmic scales
Einstein's theory of general relativity has been tested — and confirmed — on scales far beyond those of our Solar System. But the results don't exclude all alternative theories of gravity.
- J. Anthony Tyson
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News |
Volunteer army catches interstellar dust grains
Stardust mission finds particles that represent the building blocks of the Solar System.
- Eric Hand
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News |
Light extinguishes dark-matter claims
Starlight accounts for anomalous electron signals.
- Eric Hand
Vela pulsar wind nebula X-rays are polarized to near the synchrotron limit