Objects with only 6.7 per cent of the sun’s mass can be stars, according to a fresh measurement of how massive an object must be to achieve nuclear fusion

Some extremophile bacteria could survive the a crash-landing of a meteorite or spacecraft, helping them travel between worlds

Signs of water in a gas giant exoplanet’s atmosphere suggest the world formed much closer to its star than gas giants in our solar system did

Ghana telescope heralds first pan-African array

Nature 545, 7653 (2017). http://www.nature.com/doifinder/10.1038/545144a

Author: Sarah Wild

By converting a defunct communications dish, astronomers are breaking ground on Earth and beyond.

Multi-phase volcanic resurfacing at Loki Patera on Io

Nature 545, 7653 (2017). doi:10.1038/nature22339

Authors: K. de Kleer, M. Skrutskie, J. Leisenring, A. G. Davies, A. Conrad, I. de Pater, A. Resnick, V. Bailey, D. Defrère, P. Hinz, A. Skemer, E. Spalding, A. Vaz, C. Veillet & C. E. Woodward

The Jovian moon Io hosts the most powerful persistently active volcano in the Solar System, Loki Patera. The interior of this volcanic, caldera-like feature is composed of a warm, dark floor covering 21,500 square kilometres surrounding a much cooler central ‘island’. The temperature gradient seen across areas of the patera indicates a systematic resurfacing process, which has been seen to occur typically every one to three years since the 1980s. Analysis of past data has indicated that the resurfacing progressed around the patera in an anti-clockwise direction at a rate of one to two kilometres per day, and that it is caused either by episodic eruptions that emplace voluminous lava flows or by a cyclically overturning lava lake contained within the patera. However, spacecraft and telescope observations have been unable to map the emission from the entire patera floor at sufficient spatial resolution to establish the physical processes at play. Here we report temperature and lava cooling age maps of the entire patera floor at a spatial sampling of about two kilometres, derived from ground-based interferometric imaging of thermal emission from Loki Patera obtained on 8 March 2015 ut as the limb of Europa occulted Io. Our results indicate that Loki Patera is resurfaced by a multi-phase process in which two waves propagate and converge around the central island. The different velocities and start times of the waves indicate a non-uniformity in the lava gas content and/or crust bulk density across the patera.

Best ever images of a lava lake on Jupiter’s innermost large moon reveal its surface regenerating itself, sometimes clockwise and sometimes anticlockwise

A sudden brightening of the infant sun – called an FU Orionis outburst – could have melted dust grains and made them stick together, building our world

ARIEL, THOR, and XIPE, the three candidates for the M4 medium-class mission in ESA's Science Programme, will be presented to the science community at a special event in Paris on 3 July 2017. The deadline to register for this event is 10 June.

The amount of carbon monoxide in Mars’s atmosphere suggests that any existing bacteria that feed on it make up no more than one billionth of Earth’s biomass

New video puts those stunning first images from the Cassini spacecraft's Grand Finale into context in Saturn's cloud tops

The NASA/ESA Hubble Telescope has peered across six billion light years of space to resolve extremely faint features of the galaxy cluster Abell 370 that have not been seen before. Imaged here in stunning detail, Abell 370 is part of the Frontier Fields programme which uses massive galaxy clusters to study the mysteries of dark matter and the very early Universe.

Observations from the Juno spacecraft are confounding astronomers with revelations about the weather and magnetism of our solar system's biggest planet

Signatures of extra dimensions that don’t normally affect the four dimensions we can observe could show up in the way they warp ripples in space-time

The most barren regions of the Universe are the far-flung corners of intergalactic space. In these vast expanses between the galaxies there are only a few atoms per cubic metre – a diffuse haze of hydrogen gas left over from the Big Bang. Viewed on the largest scales, this diffuse material nevertheless accounts for the majority of atoms in the Universe.  It fills the cosmic web, with its tangled strands spanning billions of light years.

Now a team of astronomers, including Alberto Rorai and Girish Kulkarni, from the University of Cambridge’s Institute of Astronomy and Kavli Institute, have made the first measurements of small-scale ripples in this primeval hydrogen gas. Although the regions of cosmic web they studied lie nearly 11 billion light years away, they were able to measure variations in its structure on scales a hundred thousand times smaller, comparable to the size of a single galaxy. Their results appear in the journal Science.

Intergalactic gas is so tenuous that it emits no light of its own. Instead astronomers study it indirectly by observing how it selectively absorbs the light coming from faraway sources known as quasars. Quasars constitute a brief hyperluminous phase of the galactic life-cycle, powered by the infall of matter onto a galaxy's central supermassive black hole.

Quasars act like cosmic lighthouses --- bright, distant beacons that allow astronomers to study intergalactic atoms residing between the quasars’ location and Earth. But because these hyperluminous episodes last only a tiny fraction of a galaxy’s lifetime, quasars are correspondingly rare in the sky, and are typically separated by hundreds of millions of light years from each other.

To probe the cosmic web on much smaller length scales, the astronomers exploited a fortuitous cosmic coincidence: they identified exceedingly rare pairs of quasars, right next to each other in the sky, and measured subtle differences in the absorption of intergalactic atoms measured along the two sightlines.

Schematic representation of the technique used to probe the small-scale structure of the cosmic web using light from a rare quasar pair Credit: Springel at al/J. Neidel MPIA 

Rorai, lead author of the study, says “One of the biggest challenges was developing the mathematical and statistical tools to quantify the tiny differences we measure in this new kind of data”. Rorai developed these tools as part of the research for his doctoral degree, and applied his tools to spectra of quasars obtained with the largest telescopes in the world. These included the 10m diameter Keck telescopes at the summit of Mauna Kea in Hawaii, as well as ESO's 8m diameter Very Large Telescope on Cerro Paranal, and the 6.5m diameter Magellan telescope at Las Campanas Observatory, both located in the Chilean Atacama Desert.

The astronomers compared their measurements to supercomputer models that simulate the formation of cosmic structures from the Big Bang to the present. “The input to our simulations are the laws of Physics and the output is an artificial Universe which can be directly compared to astronomical data. I was delighted to see that these new measurements agree with the well-established paradigm for how cosmic structures form.” says Jose Oñorbe, from the Max Planck Institute for Astronomy in Heidelberg, who led the supercomputer simulation effort. On a single laptop, these complex calculations would have required almost a thousand years to complete, but modern supercomputers enabled the researchers to carry them out in just a few weeks.

Joseph Hennawi, professor of physics at UC Santa Barbara who led the search for these rare quasar pairs, explains: “One reason why these small-scale fluctuations are so interesting is that they encode information about the temperature of gas in the cosmic web just a few billion years after the Big Bang.”

Astronomers believe that the matter in the Universe went through phase transitions billions of years ago, which dramatically changed its temperature. These phase transitions, known as cosmic reionization, occurred when the collective ultraviolet glow of all stars and quasars in the Universe became intense enough to strip electrons off the atoms in intergalactic space. How and when reionization occurred is one of the biggest open questions in the field of cosmology, and these new measurements provide important clues that will help narrate this chapter of cosmic history.

Reference
Rorai, A et al. Measurement of the small-scale structure of the intergalactic medium using close quasar pairs. Science; 28 Apr 2017; DOI: 10.1126/science.aaf9346

Astronomers have made the first measurements of small-scale fluctuations in the cosmic web 2 billion years after the Big Bang. These measurements were conducted using a novel technique which relies on the light of quasars crossing the cosmic web along adjacent lines of sight.

One of the biggest challenges was developing the mathematical and statistical tools to quantify the tiny differences we measure in this new kind of dataAlberto Rorai J. Onorbe/MPIA Volume rendering of the output from a supercomputer simulation showing part of the cosmic web 11.5 billion years ago

The text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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Portal origin URL: NASA Missions Provide New Insights into 'Ocean Worlds' in Our Solar SystemPortal origin nid: 400039Published: Thursday, April 13, 2017 - 14:00Featured (stick to top of list): noPortal text teaser: Two veteran NASA missions are providing new details about icy, ocean-bearing moons of Jupiter and Saturn, further heightening the scientific interest of these and other "ocean worlds" in our solar system and beyond. The findings are presented in papers published Thursday by researchers with NASA’s Cassini mission to Saturn and Hubble Space TelescopPortal image: This illustration shows Cassini diving through the Enceladus plume in 2015.Science Categories: Universe

The Small Magellanic Cloud galaxy is a striking feature of the southern sky even to the unaided eye. But visible-light telescopes cannot get a really clear view of what is in the galaxy because of obscuring clouds of interstellar dust. VISTA’s infrared capabilities have now allowed astronomers to see the myriad of stars in this neighbouring galaxy much more clearly than ever before. The result is this record-breaking image — the biggest infrared image ever taken of the Small Magellanic Cloud — with the whole frame filled with millions of stars.

Most binary neutron stars are thought to spin ever faster as they devour their companions - but some slow down, and it could be to do with their gassy meals

The Cassini spacecraft is beginning its final set of daring orbits with breathtaking images of the Saturn system and rings