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Volume 4 Issue 11, November 2020

Going with the flow

The interstellar medium is composed of vast flows of gas and dust at densities that vary across many orders of magnitude. Here, Henshaw et al. measure velocities across hugely different distances, finding that velocity and density fluctuations are ubiquitous and connected across spatial scales and galactic environments.

See Henshaw et al.

Image: T Müller/J. D. Henshaw/MPIA/PHANGS Cover Design: Bethany Vukomanovic.


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Comment & Opinion

  • The historic launch of the first several hundred out of 12,000 planned Starlink satellites heralds the arrival of the era of ultra-large satellite constellations. If it will bring new opportunities or insurmountable challenges to astronomy will probably depend on whether you are conducting your observations in space or from the surface of the Earth.

    • Igor Levchenko
    • Shuyan Xu
    • Kateryna Bazaka
  • The Space Academic Network made a case for a small-satellite programme for the United Kingdom to provide access to space, and a route for advancing science and technology; however, funding has not been forthcoming. The search for a killer argument for this widely supported programme continues.

    • James Endicott
  • High-performance scientific satellites are currently the exclusive domain of government-funded agencies. The team behind the Twinkle Space Mission is developing a new class of small and sustainable science satellites that leverages recent innovations in the commercial space sector.

    • Richard Archer
    • Marcell Tessenyi
    • Ben Wilcock
  • Philanthropic donations are a significant contribution to the betterment of humankind, with a large percentage dedicated to science and education. Affordable small satellites may offer philanthropists the opportunity to give students and underprivileged communities access to small space telescopes.

    • Luca Maresi
    • Alessandro Zuccaro Marchi
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News & Views

  • The measure of Titan’s incredibly large migration speed away from Saturn reveals that tidal dissipation depends on the orbital frequency. This new paradigm has many implications for the internal structure of Saturn and the history of its satellite system.

    • Aurélien Crida
    News & Views
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  • The number of small satellites has grown hugely in the past decade, from tens of satellites per year in the mid-2010s to a projection of tens of thousands in orbit by the mid-2020s. This presents both problems and opportunities for observational astronomy. Small satellites offer complementary cost-effective capabilities to both ground-based astronomy and larger space missions. Compared with ground-based astronomy, these advantages are not just in the accessibility of wavelength ranges where the Earth’s atmosphere is opaque, but also in stable, high-precision photometry, long-term monitoring and improved areal coverage. Astronomy has a long history of new observational parameter spaces leading to major discoveries. Here we discuss the potential for small satellites to explore new parameter spaces in astrophysics, drawing on examples from current and proposed missions, and spanning a wide range of science goals from binary stars, exoplanets and Solar System science to the early Universe and fundamental physics.

    • Stephen Serjeant
    • Martin Elvis
    • Giovanna Tinetti
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  • The oxygen emission at 557.7 nm, responsible for the green colour of auroras on Earth, is present in two layers at 80 and 120 km altitude on the dayside atmosphere of Mars. Simultaneous observations of the oxygen both in this visible line and in the ultraviolet could also constrain the elusive visible/ultraviolet intensity ratio of the auroral emission to a value of 16.5.

    • J.-C. Gérard
    • S. Aoki
    • B. Beeckman
  • Low-mass stars are expected to destroy their lithium content as they evolve, but this study of stars in the red clump evolutionary stage shows that their lithium abundance is on average forty times greater than at the end of the previous stage, something not predicted by theory.

    • Yerra Bharat Kumar
    • Bacham E. Reddy
    • Yuan-Sen Ting
  • Statistical analysis of velocity fluctuations in the interstellar medium (ISM) of the Milky Way and NGC 4321 show that the motion of molecular gas over scales ranging from 0.1 to 1,000 pc is similar, and consistent with that generated by a combination of gravity and turbulence. ISM structure at one scale is therefore linked to structure at other scales.

    • Jonathan D. Henshaw
    • J. M. Diederik Kruijssen
    • Jiayi Sun
  • Analysis of a catalogue of accreted stars by their radial and prograde motions has identified a 200-plus-member coherent stellar stream (called Nyx) that is likely to be the remnant of a dwarf galaxy that merged with the Milky Way.

    • Lina Necib
    • Bryan Ostdiek
    • Robyn Sanderson
  • In situ measurements from the Rosetta spacecraft reveal the presence of atomic emissions close to comet 67P’s nucleus. Such emissions are due to dissociative excitation of molecules by the interaction with the solar wind, identifying them as a form of aurora.

    • M. Galand
    • P. D. Feldman
    • J. Burch
  • Two sources of variability are reported in extreme horizontal branch (EHB) stars found in globular clusters, both related to the action of weak magnetic fields: large surface spots and very energetic flares. EHB stars in clusters can thus be linked to EHB field stars, and beyond, to other stars with radiative envelopes.

    • Y. Momany
    • S. Zaggia
    • Y. Beletsky
  • An analysis of the relation between a star’s initial mass and its final mass (as a white dwarf) reveals a kink in the initial mass range 1.65–2.10 M. This kink appears to correspond to the minimum mass required for carbon star formation in the Milky Way at solar metallicity.

    • Paola Marigo
    • Jeffrey D. Cummings
    • Piero Dal Tio
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Amendments & Corrections

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Mission Control

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