Volume 3 Issue 9, September 2019

Most binary Kuiper belt objects orbit each other in the same direction as their orbit around the Sun. New computer simulations show that such orbits may be a fingerprint of planetesimal formation from collapsing clumps of pebbles.

Young galaxies are most effective at converting gas into stars. Intense accretion of fuel is required to keep galaxies growing, but these gas streams have largely eluded observations. New instruments at optical telescopes are now uncovering clues of their existence.

Extremely deep observations of the Coma galaxy cluster with the Chandra X-ray Observatory have found that the gas between galaxies, where the vast majority of the baryons lie, is far less viscous than expected.

The European Astronomical Society awarded its most prestigious prizes during its annual meeting, the European Week of Astronomy and Space Science, held in Lyon, France, from 24 to 28 June 2019.

All trans-Neptunian objects larger than 1,000 km have satellites. A hydrodynamic simulation shows that such satellites were formed by giant impacts that happened before the migration of Neptune and that kept the satellites in a fluid-like state for 10⁴–10⁶ yr.

The predominantly prograde orientation and broad inclination distribution of trans-Neptunian binary objects is reproduced by a three-dimensional hydrodynamical simulation of planetesimal formation driven by the streaming instability, showing evidence of the activation of the streaming instability in the solar protoplanetary disk.

A comprehensive set of Hubble and Spitzer observations reveal a hydrogen-rich, low-metallicity atmosphere on the sub-Neptune exoplanet GJ 3470 b. Water vapour is detected, but the planet is surprisingly depleted in methane, possibly because of photochemical or thermal processes. Sub-millimetre-sized Mie-scattering cloud particles partially attenuate the molecular signatures at short wavelength, but are largely transparent beyond 3 µm.

Theoretical modelling of velocity maps of high-redshift Lyman α emitters indicates sufficient gas inflow to fuel the central galaxy’s star-formation rate and angular momentum, implying that cold gas accretion is building galaxies at the peak of star formation.

X-ray observations of the Coma Cluster show enhanced plasma collision rates due to either particle scattering off microfluctuations caused by plasma instabilities or transport processes that are anisotropic with respect to the local magnetic field.

A unique merger shock is found in an early phase of two clusters undergoing a major merger, propagating outward along the equatorial plane of the merger. Owing to the rapid approach of the cluster pair, the gas along the merger axis is strongly compressed.

A study of 105 nearby galaxy clusters from the Sloan survey shows that barred galaxies appear more frequently in interacting clusters, indicating that cluster–cluster interaction can play an important part in bar formation.

Fragkou et al. present multiple pieces of evidence for the association of planetary nebula BMP J1613-5406 with Galactic open star cluster NGC 6067. Stars in the cluster evolve off the main sequence at about 5 solar masses, suggesting that this planetary nebula had a massive progenitor and supporting theoretical predictions of the mass range of planetary nebula progenitors.

Tamanini and Danielski show that LISA will be sensitive enough to detect (massive) exoplanets orbiting double white-dwarf systems using gravitational waves. This population of exoplanets cannot be probed by other means, and detections will reveal potentially significant numbers of planets in the Galaxy and Magellanic Clouds.

A stacked series of lithographed polymer disks could provide a lightweight and modular optics system for a future hard X-ray telescope, retaining the angular resolution of current telescopes, but improving on effective area.

As the CHaracterising ExOPlanet Satellite (CHEOPS) is scheduled for launch later this year, European Space Agency (ESA) Project Scientist Kate Isaak and Principal Investigator Willy Benz give an overview of ESA’s first science mission dedicated to the follow-up of known exoplanets orbiting bright stars.