The IOASA calls on our community to develop and implement specific actions to help achieve the aims of the 2016 Paris Agreement on climate change. The study of astronomy provides all citizens a unique perspective and view of the Universe that highlights the fragility of life on planet Earth. The first Kavli–IOASA interdisciplinary symposium will be dedicated to climate change on planets in late 2022 or early 2023.

The International Organization for Astronomical Studies Advancement (IOASA) joins other astronomy institutions and scientific organisations in stressing the importance and urgency of environmental sustainability for the future of our planet. As concluded by the International Panel on Climate Change (IPCC) [1] and highlighted in many scientific reports, increases in anthropogenic carbon dioxide and other greenhouse gases have exacerbated climate change since the industrial revolution, and without mediation, we risk extreme and irreversible damage to life on our planet. The IOASA calls on our community to develop, promote and implement specific actions to help achieve the aims of the 2016 Paris Agreement.

The study of astronomy provides all citizens a unique perspective and view of the Universe that highlights the fragility of Earth’s biosphere. Additionally, through comparative studies of planetary atmospheres, astronomers can model and measure the impact of greenhouse gases and their consequences for climate and climate change on planets.

The IOASA applauds and acknowledges the steps its members are already taking to help protect our climate — from individual organizations that publish their own carbon budgets, to organisations like Astronomers for Planet Earth. The IOASA, through its four Offices (OAD, OAO, OYA, OAE), strongly encourages and supports teaching and communicating about the Earth’s climate and the consequences of human activity, and we urge our national and individual members to address climate change in connection with their scientific, educational, outreach, and other societal activities.

As one step towards addressing this global problem, the IOASA will issue a special call for the first Kavli–IOASA interdisciplinary symposium, dedicated to Climate and Climate Change on Planets, to take place in late 2022 or early 2023. The symposium will draw from members of the IOASA as well as other relevant unions (such as GeoUnions). One goal of the symposium will be to produce an IOASA Springboard for Climate Action, directed to the astronomy community, that will recommend mitigating actions that can be undertaken at the individual, institutional, and IOASA level.

The Shaw Prize in Astronomy 2021 is shared equally by Victoria M. Kaspi, Professor of Physics and Director of McGill Space Institute, McGill University, Canada and Chryssa Kouveliotou, Professor and Chair, Department of Physics at George Washington University, USA for their contributions to our understanding of magnetars, a class of highly magnetised neutron stars that are linked to a wide range of spectacular, transient astrophysical phenomena. This prestigious award is one way in which the Shaw Prize Foundation seeks to promote astronomy, a mission shared by the IOASA and one which the two organisations have ongoing collaborations to pursue.

Through the development of new and precise observational techniques, Victoria M. Kaspi and Chryssa Kouvelioto confirmed the existence of neutron stars with ultra-strong magnetic fields and characterised their physical properties. Their work has established magnetars as a new and important class of astrophysical objects.

Neutron stars are the ultra-compact remnants of stellar explosions. Most are rapidly rotating with periods of milli-seconds to seconds and emit powerful beams of electromagnetic radiation (observed as pulsars). As such they are accurate ‘cosmic clocks’ that enable tests of fundamental physics in the presence of a gravitational field many billion times stronger than Earth’s. Reflecting their importance, the Nobel Prize in Physics has been awarded twice for work on pulsars (in 1974 and 1993).

Pulsars also have strong magnetic fields, since the magnetic field lines in the progenitor star are ‘frozen in’ in the stellar remnant as it collapses to become a neutron star. These magnetic fields funnel jets of particles along the magnetic poles, but classical radio pulsars are powered mainly by rotational energy and slowly spin down over their lifetimes.

The research carried out by Kaspi and Kouveliotou was motivated by the theoretical prediction that neutron stars with extreme magnetic fields up to a thousand times stronger than those in regular pulsars could form if dynamo action were efficient during the first few seconds after gravitational collapse in the core of the supernova. Such objects (termed magnetars) would be powered by their large reservoirs of magnetic energy, rather than by rotation, and were predicted to produce highly-energetic bursts of gamma-rays through the generation of highly energetic ionised particle pairs at their centres.

From observations of a class of X-ray/gamma-ray sources called “soft gamma-ray repeaters” (SGRs) Chryssa Kouveliotou and her colleagues in 1998–99 established the existence of magnetars and provided a stunning confirmation of the magnetar model. By developing new techniques for pulse timing at X-ray wavelengths and applying these to data from the Rossi X-ray timing satellite (RXTE), Kouveliotou in 1998 was able to detect X-ray pulses with a period of 7.5 seconds within the persistent X-ray emission of SGR 1806-20. She then measured a spin-down rate for the pulsar, and derived both the pulsar age and the dipolar magnetic field strength — which lay within the range of values predicted for magnetars, close to 1014 gauss (1010 T). The spin-down measurements were extremely challenging because of the faintness of the pulsed signal and the need to correct the rotation phase across multiple epochs.

Victoria Kaspi showed that a second class of rare X-ray emitting pulsars, the anomalous X-ray pulsars (AXPs), were also magnetars. Kaspi took the techniques used by radio astronomers to maintain phase coherence in pulsar timing and adapted them to work in the much more challenging X-ray domain. This allowed her to make extremely accurate timing measurements of X-ray pulsars with full phase coherence across intervals of months to years, and hence to measure spin-down rates far smaller than those seen in SGR 1806-20. Kaspi has also made fundamental contributions to the characterisation of magnetars as a population, through the elucidation of their physical properties and their relationship to the classical radio pulsars. Her work has cemented the recognition of magnetars as a distinct source class. Today, magnetars are routinely invoked to explain the physics underlying a diverse range of astrophysical transients including gamma-ray bursts, superluminous supernovae and nascent neutron stars.

Magnetars probe extreme physical conditions inaccessible on Earth, such as strong gravity, ultra-nuclear densities and the strongest magnetic fields in the Universe. In this high energy environment particle-antiparticle pairs are created from the vacuum, and unique tests of general relativity and quantum electrodynamics become possible. In 2020–2021, the first associations of a Galactic magnetar with millisecond duration outbursts of radio emission, so called Fast Radio Bursts (FRBs), were established. These results may suggest that “flaring” magnetars are the central engines of at least some of the spectacular extragalactic FRBs. Future studies will undoubtedly shed further light on these exciting discoveries.

The Shaw Prize 2021 recognises the seminal contributions of Victoria M. Kaspi and Chryssa Kouveliotou to the understanding of the enigmatic properties of magnetars, pulsars and gamma-ray bursts.