Comment in 2017

Pulsar timing arrays may well be the next type of experiment to detect gravitational waves. Sensitive to lower frequencies than LIGO–Virgo, they will detect the stochastic background of massive binary black hole mergers.

Pulsars — fast-spinning neutron stars — are precision clocks provided by nature. Finding pulsars in the Galactic Centre orbiting Sagittarius A*, the closest supermassive black hole to the Earth, will offer unprecedented opportunities to test general relativity and its alternatives.

Through involvement in CHIME, ALMA, the Jansky VLA and the Murchison Widefield Array, Canada is well placed in current radio astronomy facilities and the future looks even brighter, with strategic interest in the SKA and the Next Generation VLA.

Complex organics are now observed throughout the Universe, forming in the circumstellar environments over thousands of years and providing materials for star formation. Did the Earth inherit any of these organics at the time of its formation?

Active galactic nuclei (AGNs) are empirically divided into ‘radio-loud’ and ‘radio-quiet’. These 50-year-old labels are obsolete, misleading and wrong. I argue that AGNs should be classified as ‘jetted’ and ‘non-jetted’ based on a physical difference — the presence (or lack) of strong relativistic jets.

US astronomy decadal surveys advise government on how to optimize the scientific return on national investments in astronomy research. The 2020 survey will guide our community into the future, but current strains in an otherwise world-leading astronomy programme may affect this collective exercise.

We all harbour subconscious expectations about people based on their apparent membership of groups, such as gender, ethnicity or age. Research shows that these expectations can lead us to undervalue some people's contributions, inhibiting their success and thus negatively impacting our entire field.

Over the last decade, significant attention has been drawn to the gender ratio of speakers at conferences, with ongoing efforts for meetings to better reflect the gender representation in the field. We find that women are significantly under-represented, however, among the astronomers asking questions after talks.

Considerable progress has been made in the past decade to increase diversity in astronomy, and in particular to reach a ‘critical mass’ of women. It is however important to realize that this progress has mainly been the result of the selective inclusion of women from more privileged backgrounds.

There is an ongoing discussion about the participation of women in science and particularly astronomy. Demographic data from NASA's robotic planetary spacecraft missions show women scientists to be consistently under-represented.

We are at an interesting juncture in cosmology. Despite vast improvements in the measurement accuracy of the Hubble constant, a recent tension has arisen that is either signalling new physics or as-yet unrecognized uncertainties.

Can the recent Discovery mission selections be used as tea leaves to understand the future directions of NASA? In an age of many programmes being used to advance administrative and programmatic goals, Discovery appears to be driven almost entirely by science and by NASA's goal of cheaper missions.

The scientific aims of the European Space Agency's International Gamma-Ray Astrophysics Laboratory are considerably extended because of its unique capability to identify electromagnetic counterparts to sources of gravitational waves and ultra-high-energy neutrinos.

A phenomenon recently studied in theoretical physics may hold considerable interest for astronomers: the explosive decay of primordial black holes through quantum tunnelling. Their detection would be of major theoretical importance.

Black holes present a profound challenge to our current foundations of physics, and an exciting era of astronomy is just opening in which gravitational-wave observation and very-long-baseline interferometry may provide important hints about the new principles of physics needed.

Millimetre-wavelength interferometry and gravitational-wave detectors currently provide the most stringent tests for the existence of cosmic black holes. Complementary measurements of magnetic fields near their event horizon would be decisive.

As scientists, the terminology we choose influences our thinking as it carries our messages to colleagues and the public. In the face of pressure to turn science into clickbait, maintaining precision in the language we use is critical to dispel misinformation and, more broadly, to enable scientific progress.

We have found many Earth-sized worlds but we have no way of determining if their surfaces are Earth-like. This makes it impossible to quantitatively compare habitability, and pretending we can risks damaging the field.

Scientists are comfortable in their own communities but other groups working on similar phenomena at different length scales could provide unexpected insights. Collaborations are more likely to uncover common underlying principles.