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NASA’s Juno mission captured these views of Jupiter during its 59th close flyby of the giant planet on March 7, 2024. They provide a good look at Jupiter’s colorful belts and swirling storms, including the Great Red Spot. Close examination reveals something more: two glimpses of the tiny moon Amalthea (see Figure B below).

Figure B NASA’s Juno mission captured these views of Jupiter during its 59th close flyby of the giant planet on March 7, 2024. They provide a good look at Jupiter’s colorful belts and swirling storms, including the Great Red Spot. Close examination reveals something more: two glimpses of the tiny moon Amalthea.Image data: NASA/JPL-Caltech/SwRI/MSSS. Image processing by Gerald Eichstädt

With a radius of just 52 miles (84 kilometers), Amalthea has a potato-like shape, lacking the mass to pull itself into a sphere. In 2000, NASA’s Galileo spacecraft revealed some surface features, including impact craters, hills, and valleys. Amalthea circles Jupiter inside Io’s orbit, which is the innermost of the planet’s four largest moons, taking 0.498 Earth days to complete one orbit.

Amalthea is the reddest object in the solar system, and observations indicate it gives out more heat than it receives from the Sun. This may be because, as it orbits within Jupiter’s powerful magnetic field, electric currents are induced in the moon’s core. Alternatively, the heat could be from tidal stresses caused by Jupiter’s gravity.

At the time that the first of these two images was taken, the Juno spacecraft was about 165,000 miles (265,000 kilometers) above Jupiter’s cloud tops, at a latitude of about 5 degrees north of the equator.

Citizen scientist Gerald Eichstädt made these images using raw data from the JunoCam instrument, applying processing techniques to enhance the clarity of the images.

JunoCam’s raw images are available for the public to peruse and process into image products at https://missionjuno.swri.edu/junocam/processing. More information about NASA citizen science can be found at https://science.nasa.gov/citizenscience and https://www.nasa.gov/solve/opportunities/citizenscience.

More information about Juno is at https://www.nasa.gov/juno and https://missionjuno.swri.edu. For more about this finding and other science results, see https://www.missionjuno.swri.edu/science-findings.

Image credit:
Image data: NASA/JPL-Caltech/SwRI/MSSS
Image processing by Gerald Eichstädt

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Details Last Updated May 13, 2024 Related Terms

• Jet Propulsion Laboratory
• Juno
• Jupiter
• Jupiter Moons
• The Solar System

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Nature, Published online: 13 May 2024; doi:10.1038/d41586-024-01432-7

Nature talks to physicists about what to expect in the next months and beyond as the Sun hits its 'maximum'.

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Abstract not available

• Speaker: Georges Maynet (Geneva)
• Thursday 13 June 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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Abstract not available

• Speaker: Georges Maynet (Geneva)
• Thursday 13 June 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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arXiv:2405.06013v1 Announce Type: new Abstract: Type Ia supernovae (SNe Ia) are standarizable candles whose observed light curves can be used to infer their distances, which can in turn be used in cosmological analyses. As the quantity of observed SNe Ia grows with current and upcoming surveys, increasingly scalable analyses are necessary to take full advantage of these new datasets for precise estimation of cosmological parameters. Bayesian inference methods enable fitting SN Ia light curves with robust uncertainty quantification, but traditional posterior sampling using Markov Chain Monte Carlo (MCMC) is computationally expensive. We present an implementation of variational inference (VI) to accelerate the fitting of SN Ia light curves using the BayeSN hierarchical Bayesian model for time-varying SN Ia spectral energy distributions (SEDs). We demonstrate and evaluate its performance on both simulated light curves and data from the Foundation Supernova Survey with two different forms of surrogate posterior -- a multivariate normal and a custom multivariate zero-lower-truncated normal distribution -- and compare them with the Laplace Approximation and full MCMC analysis. To validate of our variational approximation, we calculate the pareto-smoothed importance sampling (PSIS) diagnostic, and perform variational simulation-based calibration (VSBC). The VI approximation achieves similar results to MCMC but with an order-of-magnitude speedup for the inference of the photometric distance moduli. Overall, we show that VI is a promising method for scalable parameter inference that enables analysis of larger datasets for precision cosmology.

Title to be confirmed

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• Speaker: Suhail Dhawan (KICC)
• Friday 12 July 2024, 11:30-12:30
• Venue: Ryle seminar room + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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• Speaker: Mark Krumholz (ANU)
• Friday 06 September 2024, 11:30-12:30
• Venue: Ryle seminar room + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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Prototyping a Sparse-Aperture, Segmented, Parabolic Primary Mirror Telescope for SUPERSHARP

The motivation for my research comes from the SUPERSHARP mission concept for large, unfolding, lightweight space telescopes which take advantage of unfolding segmented optics and a sparse aperture primary mirror to generate powerful observations while maintaining limited cost, mass, and volume requirements. The original motivation for the SUPERSHARP design comes from the ongoing search for life in the universe, but the technology has wider applications in both space and Earth observation. Prototyping of the optical system is integral to ensuring technological readiness of key aspects of the telescope design – in particular, the active control and maintenance of optics alignment. In this talk, I will present the work I have done designing and building a prototype of a sparse-aperture, segmented, parabolic primary mirror telescope using two mirror segments. I will also outline the immediate improvements and next steps required for the prototype to more accurately model an effective imaging system.

• Speaker: Zoe Horvath
• Wednesday 15 May 2024, 13:15-13:40
• Venue: The Hoyle Lecture Theatre + Zoom .
• Series: Institute of Astronomy Seminars; organiser: .

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Prototyping a Sparse-Aperture, Segmented, Parabolic Primary Mirror Telescope for SUPERSHARP

The motivation for my research comes from the SUPERSHARP mission concept for large, unfolding, lightweight space telescopes which take advantage of unfolding segmented optics and a sparse aperture primary mirror to generate powerful observations while maintaining limited cost, mass, and volume requirements. The original motivation for the SUPERSHARP design comes from the ongoing search for life in the universe, but the technology has wider applications in both space and Earth observation. Prototyping of the optical system is integral to ensuring technological readiness of key aspects of the telescope design – in particular, the active control and maintenance of optics alignment. In this talk, I will present the work I have done designing and building a prototype of a sparse-aperture, segmented, parabolic primary mirror telescope using two mirror segments. I will also outline the immediate improvements and next steps required for the prototype to more accurately model an effective imaging system.

• Speaker: Zoe Horvath
• Wednesday 15 May 2024, 13:15-13:40
• Venue: The Hoyle Lecture Theatre + Zoom .
• Series: Institute of Astronomy Seminars; organiser: .

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A solar storm of this scale can cause disruptions to infrastructure such as the power grid.

Sufficiently advanced aliens would be able to capture vast quantities of energy from their star using a massive structure called a Dyson sphere. Such a device would give off an infrared heat signature - and astronomers have just spotted 60 stars that seem to match

arXiv:2405.05762v1 Announce Type: new Abstract: The evolution of many astrophysical systems depends strongly on the balance between heating and cooling, in particular star formation in giant molecular clouds and the evolution of young protostellar systems. Protostellar discs are susceptible to the gravitational instability, which can play a key role in their evolution and in planet formation. The strength of the instability depends on the rate at which the system loses thermal energy. To study the evolution of these systems, we require radiative cooling approximations because full radiative transfer is generally too expensive to be coupled to hydrodynamical models. Here we present two new approximate methods for computing radiative cooling that make use of the polytropic cooling approximation. This approach invokes the assumption that each parcel of gas is located within a spherical pseudo-cloud which can then be used to approximate the optical depth. The first method combines the methods introduced by Stamatellos et al. and Lombardi et al. to overcome the limitations of each method at low and high optical depths respectively. The second, the "Modified Lombardi" method, is specifically tailored for self-gravitating discs. This modifies the scale height estimate from the method of Lombardi et al. using the analytical scale height for a self-gravitating disc. We show that the Modified Lombardi method provides an excellent approximation for the column density in a fragmenting disc, a regime in which the existing methods fail to recover the clumps and spiral structures. We therefore recommend this improved radiative cooling method for more realistic simulations of self-gravitating discs.

Do we understand cosmic structure growth? Insights from new CMB lensing measurements with the Atacama Cosmology Telescope

One of the most powerful tests of our cosmological model is to verify the predicted growth of large-scale structure with time. Intriguingly, many recent measurements have reported small discrepancies in such tests of structure growth (“the S8 tension”), which could hint at systematic errors or even new physics. Motivated by this puzzling situation, I will present new determinations of cosmic structure growth using CMB gravitational lensing measurements from the Atacama Cosmology Telescope (ACT). These ACT DR6 CMB lensing measurements allow us to directly map the dark matter distribution in projection out to high redshifts; new cross-correlations of CMB lensing with unWISE galaxies also allow us to probe the matter tomographically. I will discuss the implications of our lensing results for the validity of our standard cosmological model as well as for key cosmological parameters such as the neutrino mass and Hubble constant.

• Speaker: Blake Sherwin (DAMTP)
• Tuesday 25 June 2024, 11:30-12:30
• Venue: Hoyle Lecture Theatre and online (details to be sent by e-mail).
• Series: New Frontiers in Astrophysics: A KICC Perspective; organiser: Steven Brereton.

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Non-smooth horizons in Kerr black hole mergers

Dynamical black holes are known to develop non-smooth structures on their horizon. We begin by reviewing a classification of all generic non-smooth structures that may appear on black hole horizons in four-dimensional spacetimes. Introducing a time function, we describe how two of these features – namely creases and caustics – evolve, and in particular discuss processes known as ‘perestroikas’, where the non-smooth structure on a horizon cross-section changes qualitatively. We then study the merger of two Kerr black holes in the extreme mass ratio limit, and focus on the creases and caustics that are present on the horizon. We explain how our results differ from an older analysis of the same system by Emparan et al., and show that these novel results are consistent with the properties of creases expected generically. This talk is based on work done with Harvey Reall and Robie Hennigar.

• Speaker: Maxime Gadioux, DAMTP, University of Cambridge
• Friday 17 May 2024, 13:00-14:00
• Venue: Potter room/Zoom.
• Series: DAMTP Friday GR Seminar; organiser: Xi Tong.

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NASA-JPL/Caltech; image processing by IPAC/Robert Hurt

This image, released on May 9, 2024, from NASA’s retired Spitzer Space Telescope shows streams of dust flowing toward the supermassive black hole at the heart of the Andromeda Galaxy. These dust streams can help explain how black holes billions of times the mass of our Sun can satiate their big appetites but remain “quiet” eaters.

Read on to learn how data from Spitzer helped shed light on how some black holes consume gas and dust.

Image Credit: NASA-JPL/Caltech

For decades, cosmologists have been fighting over the Hubble constant, a number that represents the expansion rate of the universe – it may have finally been pinned down

The Red Planet launches large bursts of plasma into space from its upper atmosphere, much like the sun’s coronal mass ejections, despite not having a global magnetic field

Surprising recent measurements hint that the universe isn’t expanding in the way we had thought, and it could be explained by still-theoretical dark radiation

Attractor reconstruction of active stellar light curves

Stellar activity is notoriously difficult to model, being neither periodic nor purely stochastic. In light curves, the interplay between the stellar rotation period and the birth and death of spots and faculae gives rise to quasi-periodic modulation over time scales of hours to weeks. Despite the complexity of this interplay, the resulting light curves bear strong qualitative resemblance to systems known to exhibit low-dimensional dynamical chaos, such as the Rössler attractor.

In the 1980s and 1990s, a suite of techniques for nonlinear dynamical analysis, called attractor reconstruction, evolved to study exactly this type of system. Attractor reconstruction works by embedding a 1-dimensional time series, such as stellar light curve, in a higher-dimensional phase space capable of capturing its full dynamical behavior: too low a dimensionality, and the system’s trajectory will self-intersect and tangle, which we know to be physically unrealistic given the non-periodicity of the observed signal. This technique has been used successfully to model the historical sunspot record and the light curves of variable stars (both simulated and observed) and to recover important features of their underlying dynamics, including their dimensionality and the time scales over which they can be meaningfully forecast into the future. Here, I discuss the application of attractor reconstruction to the light curve of the Sun over Solar cycles 23-25, as observed by the Solar and Heliospheric Observatory.

• Speaker: Emily Sandford (Cavendish)
• Tuesday 14 May 2024, 13:00-14:00
• Venue: Ryle seminar room + ONLINE - Details to be sent by email.
• Series: Exoplanet Seminars; organiser: Dr Dolev Bashi.

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Convection, waves and mixing in stars: insights and challenges from numerical simulations

The lifecycle of stars is profoundly shaped by the internal transport and mixing of chemical elements. Within most stars, regions of convective motions and stable stratification coexist, separated by so-called convective boundaries. While convective regions are very efficient at mixing chemical species, stably stratified regions mostly inhibit the vertical transport of elements. Current models suggest that mixing beyond convective regions is needed to explain observed stellar properties. Waves, excited by convection at convective boundaries, could play a crucial role by providing additional mixing in the vertical direction.

In this talk, I will highlight results from recent numerical simulations with the MUSIC code on the study of waves, convection, and mixing in stars. I will discuss challenges in measuring vertical mixing and transport by waves in numerical simulations, and present some prospects for improving our understanding of mixing mechanisms through numerical experiments.

• Speaker: Thomas Guillet (Exeter)
• Monday 13 May 2024, 14:00-15:00
• Venue: MR14 DAMTP and online.
• Series: DAMTP Astrophysics Seminars; organiser: Roger Dufresne.

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