Um experimento com sons saturninos através do Design Editorial

Em 1977, a Nasa lançou as sondas Voyager 1 e 2 em direção aos quatro planetas gasosos do nosso Sistema Solar com a missão de estudar os confins do Universo. Junto aos motores, processadores, antenas e máquinas fotográficas, elas ainda transportam o Disco de Ouro, contendo informações sobre o planeta Terra, caso alguém cruze seu caminho e tenha interesse em ouvir umas das sinfonias de Bath ou cantos de pássaros. Durante a viagem, elas captam ondas eletromagnéticas espaciais sobre os corpos celestes e enviam aos cientistas para serem estudados. Por vezes alguns desses dados são transformados em áudios para que também possamos escutar os sons do Universo. Ao fazer essa transição tornando os dados inteligíveis, os cientistas não apenas estão criando música, mas também possibilitando estudos que possam aprofundar os conhecimentos sobre os planetas. Sendo assim, ao transformar dados de um meio ao outro tornando capaz sua apreensão, os cientistas estariam “materializando” essas informações. Diante disso, este artigo apresenta um recorte do trabalho de conclusão de curso [Título omitido para revisão cega] do bacharelado em Design Gráfico da Universidade Federal de Pelotas. O projeto propõe desenvolver um livro experimental intitulado Voyager Sounds que possui como composição os áudios criados pela Nasa a partir de dados obtidos pelas sondas Voyager 1 e Voyager 2 em 1977 do planeta Saturno. Com o auxílio da tecnologia, utilizando a técnica de databending, os áudios foram recodificados e transformados em linguagem visual, explorando as diversas áreas de percepção de sentidos e estabelecendo relações de remediação entre os meios visual e sonoro.

Atmospheric implications of the lack of H 3 + detection at Neptune

H 3 + has been detected at all of the solar system giant planets aside from Neptune. Current observational upper limits imply that there is far less H 3 + emission at Neptune than rudimentary modelling would suggest. Here, we explore via modelling a range of atmospheric conditions in order to find some that could be consistent with observational constraints. In particular, we consider that the upper atmosphere might be much cooler than it was during the 1989 Voyager 2 encounter, and we examine the impact of an enhanced influx of external material that could act to reduce H 3 + density. Resulting ionosphere models that are consistent with existing H 3 + observational constraints have an exospheric temperature of 450 K or less, 300 K lower than the Voyager 2 value. Alternatively, if a topside CO influx of 2 × 10 8 cm −2 s −1 is imposed, the upper atmospheric temperature can be higher, up to 550 K. The potential cooling of Neptune’s atmosphere is relevant for poorly understood giant planet thermospheric energetics, and would also impact aerobreaking manoeuvers for any future spacecraft. Such a large CO influx, if present, could imply Triton is a very active moon with prominent atmospheric escape, and/or that Neptune’s rings significantly modify its upper atmosphere, and the introduction of so much exogenic material would complicate interpretation of the origin of species observed in Neptune’s lower atmosphere. This article is part a discussion meeting issue ‘Future exploration of ice giant systems’.

Lessons learned from (and since) the Voyager 2 flybys of Uranus and Neptune

More than 30 years have passed since the Voyager 2 flybys of Uranus and Neptune. This paper outlines a range of lessons learned from Voyager, broadly grouped into ‘process, planning and people.’ In terms of process, we must be open to new concepts, whether new instrument technologies, new propulsion systems or operational modes. Examples from recent decades that could open new vistas in the exploration of the deep outer Solar System include the Cassini Resource Exchange and the ‘sleep’ mode from the New Horizons mission. Planning is crucial: mission gaps that last over three decades leave much scope for evolution both in mission development and in the targets themselves. The science is covered in other papers in this issue, but this paper addresses the structure of the US Planetary Decadal Surveys, with a specific urging to move from a ‘destination-based’ organization to a structure based on fundamental science. Coordination of distinct and divergent international planning timelines brings both challenges and opportunity. Complexity in the funding and political processes is amplified when multiple structures must be navigated; but the science is enriched by the diversity of international perspectives, as were represented at the Ice Giant discussion meeting that motivated this review. Finally, the paper turns to people: with generational-length gaps between missions, continuity in knowledge and skills requires careful attention to people. Lessons for the next generation of voyagers include: how to lead and inspire; how to develop the perspective to see their missions through decades-long development phases; and cultivation of strategic thinking, altruism and above all, patience. This article is part of a discussion meeting issue ‘Future exploration of ice giant systems’.

Auroral emissions from Uranus and Neptune

Uranus and Neptune possess highly tilted/offset magnetic fields whose interaction with the solar wind shapes unique twin asymmetric, highly dynamical, magnetospheres. These radiate complex auroral emissions, both reminiscent of those observed at the other planets and unique to the ice giants, which have been detected at radio and ultraviolet (UV) wavelengths to date. Our current knowledge of these radiations, which probe fundamental planetary properties (magnetic field, rotation period, magnetospheric processes, etc.), still mostly relies on Voyager 2 radio, UV and in situ measurements, when the spacecraft flew by each planet in the 1980s. These pioneering observations were, however, limited in time and sampled specific solar wind/magnetosphere configurations, which significantly vary at various timescales down to a fraction of a planetary rotation. Since then, despite repeated Earth-based observations at similar and other wavelengths, only the Uranian UV aurorae have been re-observed at scarce occasions by the Hubble Space Telescope. These observations revealed auroral features radically different from those seen by Voyager 2, diagnosing yet another solar wind/magnetosphere configuration. Perspectives for the in-depth study of the Uranian and Neptunian auroral processes, with implications for exoplanets, include follow-up remote Earth-based observations and future orbital exploration of one or both ice giant planetary systems. This article is part of a discussion meeting issue ‘Future exploration of ice giant systems’.

The orbit of Triton with new precise observations and the INPOP19a ephemeris

Aims. The Gaia catalogue brings new opportunities and challenges to high-precision astronomy and astrometry. The precision of data reduction is therefore improved by a large number of reference stars with high-precision positions and proper motions. Numerous precise positions for Triton are obtained from the latest observations using the Gaia catalogue. Furthermore, the new INPOP19a planetary ephemeris, which also fits the observations from the Gaia Data Release 2, has recently become available. In this paper, a new orbit of Triton is calculated using the latest precise charge-coupled device (CCD) observations and the INPOP19a ephemeris. Methods. Triton’s orbital solution is calculated using a numerical integrator, while the orientation of Neptune’s pole in particular is obtained by integrating the simplified Euler’s equations of motion. We determine the orbit of Triton over 170 yr based on 11 040 Earth-based observations made between 1847 and 2016 and on Voyager 2 data. The positions of the Sun and planets are provided by the INPOP19a ephemeris. We compare our results to those from other previous works to check the influences on Triton’s orbit from different planetary ephemerides. Results. A new orbit of Triton is provided here. The root-mean-square of the residuals for the Earth-based CCD absolute observations are 0.102″ in right ascension and 0.142″ in declination. Although most different planetary ephemerides have large differences in Neptune’s position, the orbits of Triton using different planetary ephemerides are still close, under similar dynamical models. The Voyager 2 data add a constraint on Triton’s orbit here.