Volume 5 Issue 9, September 2021

The missing baryon problem may now be resolved, but the exact location and physical properties of the diffuse component remains unclear. This problem could be tractable, but requires a combination of new galaxy redshift surveys and new X-ray and radio facilities.

When do we stop an ongoing science project to make room for something new? Decision-making is a complex process, ranging from budgetary considerations and tension between ongoing projects, to progress assessments and allowance for novel science developments.

The climate crisis is no longer a prediction for the future, it is happening here and now. Astronomers have realized that they need to become part of the solution and are working towards reducing their own carbon footprint as well as communicating an astronomical perspective.

Astronomers are trusted voices in the communication of science; our community should resist inundating people with facts and figures but use its advantage to encourage the public to listen to climate change experts and encourage the need for urgent cross-sectoral systemic change.

Astronomers are used to advocating for (financial) support for their future endeavours, but how should they go about lobbying for support for issues such as the climate emergency? Join forces with those experienced in effecting policy change.

Our view of fast radio bursts — millisecond duration pulses of high intensity — has gained significant clarity following the discovery of hundreds of sources that are helping us to understand the nature of this enigmatic phenomenon.

Novel observational evidence appears to confirm that when mass is supplied to massive black holes at low rates, only a fraction is actually accreted. Much of the gas may be lost in a low-speed magnetohydrodynamic wind.

The standard model of terrestrial planet formation ignores the role of orbital migration of planetary embryos. A new scenario shows how migration may have sculpted the inner Solar System’s orbital architecture, as long as embryos converged towards about 1 au.

The association of a short gamma-ray burst with a core-collapse supernova seems to challenge current scenarios for the origin of these extreme events. But how much can we rely on observed duration for pinpointing their progenitors?

By focusing on the topic of stellar dynamics and stellar populations of the Milky Way and its siblings, a recent virtual meeting aimed at connecting both fields, each of which brings unique perspectives to understanding how disk galaxies form and evolve.

The concepts and development milestones of the two Chinese space-based gravitational wave observatories, TianQin and Taiji, are introduced. Considering their similar goals and operation window with LISA, possible collaborations among them are discussed.

A full 2D radiation–hydrodynamic model of a protoplanetary disk shows that rocky planets can be formed early, and not tens of million years after the dispersal of the gas disk as usually assumed, by means of gas-driven migration of planetesimals around 1 au. The model reproduces well the structure of the inner Solar System.

Electron-capture supernovae are thought to come from progenitors with a narrow range of masses, and thus they are rare. Here the authors present six indicators of an electron-capture supernova origin, and find that supernova 2018zd fulfils all six criteria.

A gamma-ray burst (GRB) is reported to show a sharp 1-second spike, characteristic of short GRBs, but with other observational properties resembling those of long GRBs. This burst may belong to a class of core-collapse-origin GRBs with genuinely short durations.

The spectral properties of a short gamma-ray burst indicate that, contrary to expectations, it arose from the collapse of a massive star rather than from a compact binary merger. This discovery also confirms that most collapsars do not produce ultra-relativistic jets.

Chandra X-ray spectroscopy reveals a 10⁸ K plasma outflow in the low-luminosity active galactic nucleus M81. Magnetohydrodynamical simulations show this energetic wind to originate from a hot accretion flow and impact its host galaxy.

X-Ray diffraction data from the Curiosity rover found evidence of glauconitic clays, which are sensitive to the duration of sedimentary conditions within bodies of water. This result is indicative of a low-temperature aqueous environment that remained in a steady state for extended periods of time, favouring its habitability.

Three years of observations with the ExoMars TGO Atmospheric Chemistry Suite have clarified the mechanism of atmospheric water loss from Mars, and particularly the fraction of deuterium compared with hydrogen. Analysis of several isotopologues of water in the mid-atmosphere of Mars shows that atomic H and D are produced at perihelion in relative amounts controlled by photolysis. These atoms are able to escape from the atmosphere.

Modelling shows that impact gardening on Europa has the potential to churn the shallow subsurface material down to 30 cm very efficiently and globally, thus destroying potential habitable niches just below the surface. Some areas where both gardening and radiation are relatively weak are, however, identified.

The black holes in Galactic globular cluster Palomar 5 have been throwing their weight around and ejecting the stellar component of the cluster, creating its tidal tail and sparse appearance. Models predict that a billion years in the future the cluster will be composed entirely of stellar-mass black holes.

The CONCERTO instrument paves the way to large field-of-view spectro-imagers operating at (sub-)millimetre wavelengths, write Instrument Scientist Alessandro Monfardini and Principal Investigator Guilaine Lagache.