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Volume 3 Issue 11, November 2019

Voyager 2 breaks out of the bubble

After 41 years of travel, Voyager 2 exited the heliosphere on 5 November 2018 at a distance of 119 au. This issue features five papers reporting plasma, particle and magnetic field measurements from the heliosheath, heliopause and interstellar medium, and their implications for our knowledge of the heliosphere.

See Krimigis et al., Burlaga et al., Stone et al., Richardson et al., Gurnett and Kurth, and News & Views by Strauss.

Image: Ben C. Smith, Johns Hopkins-APL/NASA/JPL. Cover Design: Allen Beattie.


  • As Nature turns 150, we look back on its close connection to the Nobel Prize in Physics and some of the most epoch-defining papers in astronomy.



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Comment & Opinion

  • Researchers are debating whether habitability is a binary concept or not. We propose that the habitability of environments is a continuum defined by a series of binary questions.

    • Charles S. Cockell
    • Adam H. Stevens
    • R. Prescott
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Books & Arts

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Research Highlights

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News & Views

  • After 41 years of travel, the Voyager 2 spacecraft joins its twin in interstellar space. A suite of papers report Voyager 2’s experience of its transition through the heliosheath and heliopause to what lies beyond.

    • R. Du Toit Strauss
    News & Views
  • Seventy years after the first detection of interstellar magnetic fields, experts met in Newcastle upon Tyne, UK, on 10–14 June 2019, to discuss new perspectives on interstellar magnetic fields from small to large scales, from the Milky Way to distant galaxies and from observations to theories and simulations.

    • Andrew Fletcher
    • Sui Ann Mao
    Meeting Report
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  • Measurements from Cassini’s Grand Finale, when the spacecraft flew between Saturn and its rings, have been used to claim that the rings are much younger than the planet itself. However, this interpretation does not solve all of the inconsistencies, and the question of the age of Saturn’s rings is still open.

    • Aurélien Crida
    • Sébastien Charnoz
    • Luke Dones
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  • The MASCOT lander observed a boulder on the surface of asteroid Ryugu up close. The boulder’s low thermal inertia is closer to fine regolith or comets rather than stony boulders, indicating high porosity and low tensile strength. Orbit measurements confirm that Ryugu’s surface is covered with similar boulders.

    • M. Grott
    • J. Knollenberg
    • A. Moussi-Soffys


  • The measurement of faint fluxes of photons from across the Universe requires sensitive terahertz detectors, cooled to minimize noise. By using a photomixer with plasmonics-based semiconductors to downconvert the high frequencies, terahertz detection can be accomplished at room temperature.

    • Ning Wang
    • Semih Cakmakyapan
    • Mona Jarrahi
  • Graphene doped to the Dirac point can be used to detect signals from 90 to 700 GHz, and prospectively across the entire terahertz range, with high sensitivity. Such a sensor could be used in next-generation space-based telescopes, promising quantum-limited detection that surpasses superconducting technologies.

    • S. Lara-Avila
    • A. Danilov
    • S. Kubatkin
  • By using a superconducting integrated circuit to filter incoming millimetre, submillimetre and far-infrared light from distant galaxies, a prototype spectrometer holds promise for wideband spectrometers that are small, sensitive and scalable to wideband spectroscopic imagers.

    • Akira Endo
    • Kenichi Karatsu
    • Jochem J. A. Baselmans
  • Measurements of energetic ions and electrons with the Low-Energy Charged Particle instrument on Voyager 2 are presented from the boundary of the heliosphere and from the interstellar medium. Voyager 2’s heliopause crossing bears some similarity to that of Voyager 1, despite differing solar wind conditions.

    • Stamatios M. Krimigis
    • Robert B. Decker
    • Louis J. Lanzerotti
  • This paper reports measurements of the magnetic fields and energetic particles detected by the Voyager 2 spacecraft as it passed from the heliosphere, through the heliosheath and heliopause, to the interstellar medium. As predicted by models, Voyager 2 encountered a ‘magnetic barrier’ before reaching the heliopause.

    • L. F. Burlaga
    • N. F. Ness
    • J. D. Richardson
  • As it crossed the heliopause, Voyager 2 observed a sharp decrease in measurements of the low-energy ions that originate within the heliosphere, and an increase in the cosmic rays from the Milky Way, without any of the precursor flux tubes that Voyager 1 experienced. Outside the heliopause, a boundary layer exists.

    • Edward C. Stone
    • Alan C. Cummings
    • Nand Lal
  • On its departure from the heliosphere, the plasma experiment on Voyager 2 observed changes corresponding to a 1.5-au-wide boundary region, followed by a much thinner boundary layer, before reaching the heliopause. Outside the heliopause, the very local interstellar medium is found to be hotter than expected. [The summary that originally appeared was incorrect and has been updated.]

    • John D. Richardson
    • John W. Belcher
    • Leonard F. Burlaga
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Amendments & Corrections

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Mission Control

  • The China Square Kilometre Array (SKA) team recently completed the first SKA regional centre prototype, marking an important leap forward towards a future large-scale deployment, explain Tao An, Xiang-Ping Wu and Xiaoyu Hong.

    • Tao An
    • Xiang-Ping Wu
    • Xiaoyu Hong
    Mission Control
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