Volume 4 Issue 1, January 2020

Soon after Einstein’s calculation of the effect of the Sun’s gravitational field on the propagation of light in 1911, astronomers around the world tried to measure and verify the value. If the first attempts in Brazil in 1912 or Imperial Russia in 1914 had been successful, they would have proven Einstein wrong.

Black hole feeding and feedback are often studied disjointly in both observations and simulations. We encourage the adoption of three physically motivated scales, linking them in a tight multiphase self-regulated loop. We pinpoint the key open questions of this unification problem and advocate for a multiwavelength, multiscale and interdisciplinary community.

The Parker Solar Probe spacecraft completed the first two of its 24 scheduled orbits around the Sun on 18 June 2019, making history by flying halfway between Mercury and the Sun.

For years, much of our understanding of the formation of circumstellar aromatic molecules has been based on laboratory flame studies. Now, results acquired using a novel experimental technique suggest that circumstellar aromatics might not be formed under the conditions we thought they were.

Every 10 years, X-ray astronomers gather in Bologna, Italy, to review the state of the field. After 30 years of these meetings, is there really still a separate field of X-ray astronomy?

This Perspective highlights the science opportunities and the vast discovery space of simultaneous observations from the LISA and Athena observatories, which would be missed if they were operated in different epochs .

Cosmochemical measurements reveal the existence of two distinct reservoirs of non-carbonaceous and carbonaceous materials, originating from the inner and outer protoplanetary disk, respectively, which separated after the first million years after the birth of the Solar System, possibly due to the rapid growth of Jupiter’s core.

Pockets of iron-rich melt within asteroids get progressively enriched in sulfur while the asteroid is cooling, generating excess pressure that can push the melt up to the surface. This ‘ferrovolcanism’ can be the origin of the stony-iron pallasite meteorites and can explain the contradicting results from asteroid 16 Psyche.

Water ice on the surfaces of asteroids can survive only up to 10⁶ years. Laboratory experiments show that space weathering by energetic particles and micrometeorites can regenerate enough water by oxidizing organics and dehydrating minerals to explain the spectral features of hydration observed on asteroid surfaces.

2I/Borisov is the first interstellar comet we know to have visited the Solar System, and the second interstellar visitor after ‘Oumuamua. Initial observations with the William Herschel Telescope and Gemini North Telescope reveal cometary features indistinguishable from Solar System comets, apart from its hyperbolic orbit.

Tidally locked exoplanets with oceans are supposed to be globally frozen except around the substellar point, where the water stays liquid—known as the eyeball state. However, if sea-ice drift is included in climate models, the open water region shrinks and can even disappear, resulting in a snowball state.

A theoretical thermonuclear runaway that converts helium to carbon in the interior of an evolved star—the helium core flash—has not yet been confirmed observationally. Asteroseismic models of hot subdwarf stars show that the helium core flash should be detectable with the Transiting Exoplanet Survey Satellite.

Cromartie et al. have probably found the most massive neutron star discovered so far by combining NANOGrav 12.5-yr data with radio data from the Green Bank Telescope. Millisecond pulsar J0740+6620 has a mass of 2.14 M_⊙, ~0.1 M_⊙ more massive than the previous record holder, and very close to the upper limit on neutron star masses from Laser Interferometer Gravitational-Wave Observatory measurements.

GRB 070809 shows an unusual optical radiation component at t ≈ 0.47 d, at odds with a forward shock afterglow. If interpreted as a kilonova, the possibility arises of using short gamma-ray bursts to identify neutron star mergers beyond LIGO’s reach.

Asteroid families created by collisions in the last ~100 Myr have a higher fraction of subfamilies than older ones. The impact produces highly rotating fragments that generate such subfamilies by fission and subsequently disperse. The final appearance of an asteroid family is thus the product of a drawn-out evolution.

An extensive survey to search for members of the only known Kuiper belt family, named after the parent body Haumea, found no family members fainter than absolute magnitude H_r = 7.9, significantly brighter than the detection limit (H_r = 9.5). This lack of small members is inconsistent with a catastrophic disruption as the origin of the Haumea family.

Using an atomic gas aggregation process in the laboratory to simulate the conditions in the inner regions of a carbon-rich evolved star, Martínez, Santoro, Merino and colleagues. show that aromatic species and fullerenes form surprisingly inefficiently, and that amorphous carbon nanograins and aliphatic clusters dominate.