Institute of Astronomy

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Star clusters could host long-lived technological civilisations

Astronomy News - 7 January 2016 - 4:47pm

We've been too quick to dismiss globular clusters of old stars as hosts of life. Old, interstellar extraterrestrials could exist there

Migrating giant planets might eat their own life-friendly moons

Astronomy News - 7 January 2016 - 4:46pm

We're actively searching for exomoons – which orbit planets around other stars – without luck. Maybe that's because they didn't survive

Cosmology: Rare isotopic insight into the Universe

Astronomy News - 7 January 2016 - 4:45pm

Cosmology: Rare isotopic insight into the Universe

Nature 529, 7584 (2016). doi:10.1038/nature16326

Authors: Nikos Prantzos

Light isotopes of hydrogen and helium formed minutes after the Big Bang. The study of one of these primordial isotopes, helium-3, has now been proposed as a useful strategy for constraining the physics of the standard cosmological model.

A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion

Astronomy News - 7 January 2016 - 4:45pm

A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion

Nature 529, 7584 (2016). doi:10.1038/nature16068

Authors: David K. Sing, Jonathan J. Fortney, Nikolay Nikolov, Hannah R. Wakeford, Tiffany Kataria, Thomas M. Evans, Suzanne Aigrain, Gilda E. Ballester, Adam S. Burrows, Drake Deming, Jean-Michel Désert, Neale P. Gibson, Gregory W. Henry, Catherine M. Huitson, Heather A. Knutson, Alain Lecavelier des Etangs, Frederic Pont, Adam P. Showman, Alfred Vidal-Madjar, Michael H. Williamson & Paul A. Wilson

Thousands of transiting exoplanets have been discovered, but spectral analysis of their atmospheres has so far been dominated by a small number of exoplanets and data spanning relatively narrow wavelength ranges (such as 1.1–1.7 micrometres). Recent studies show that some hot-Jupiter exoplanets have much weaker water absorption features in their near-infrared spectra than predicted. The low amplitude of water signatures could be explained by very low water abundances, which may be a sign that water was depleted in the protoplanetary disk at the planet’s formation location, but it is unclear whether this level of depletion can actually occur. Alternatively, these weak signals could be the result of obscuration by clouds or hazes, as found in some optical spectra. Here we report results from a comparative study of ten hot Jupiters covering the wavelength range 0.3–5 micrometres, which allows us to resolve both the optical scattering and infrared molecular absorption spectroscopically. Our results reveal a diverse group of hot Jupiters that exhibit a continuum from clear to cloudy atmospheres. We find that the difference between the planetary radius measured at optical and infrared wavelengths is an effective metric for distinguishing different atmosphere types. The difference correlates with the spectral strength of water, so that strong water absorption lines are seen in clear-atmosphere planets and the weakest features are associated with clouds and hazes. This result strongly suggests that primordial water depletion during formation is unlikely and that clouds and hazes are the cause of weaker spectral signatures.

Astrophysics: Why black holes pulse brightly

Astronomy News - 7 January 2016 - 4:43pm

Astrophysics: Why black holes pulse brightly

Nature 529, 7584 (2016). doi:10.1038/529028a

Authors: Poshak Gandhi

Black holes can produce oscillating outbursts of radiation that were thought to be associated with high rates of infalling matter. The observation of pulses of visible light from a black hole complicates this picture. See Letter p.54

Black hole caught 'burping' gas

Astronomy News - 6 January 2016 - 9:34am

Astronomers spy two huge waves of gas being "burped" by the black hole at the heart of a nearby galaxy.

Giant galaxy caught tearing apart its little neighbour

Astronomy News - 5 January 2016 - 8:51am

Two decades ago, astronomers caught the Milky Way shredding a dwarf galaxy. Now they've seen the same thing happening 11 million light-years away

Quantum Foam

Astronomy News - 3 January 2016 - 7:50am

Researchers have used NASA space telescopes to prove that space-time is much less "foamy" than some models predict. Understanding their result requires a trip into the weird world of quantum physics.

Advance 'can help find other worlds'

Astronomy News - 2 January 2016 - 7:13am

The pull of gravity on a distant star can now be measured more accurately, shedding light on other worlds, say astronomers.

Two missions face off to seek life in icy seas of Enceladus

Astronomy News - 31 December 2015 - 8:01am
NASA's Cassini spacecraft has been sampling the plumes on Saturn's moon for a decade, with no sign of microbes. Two proposed missions hope to change that

VIDEO: Is it time for more laws to govern space?

Astronomy News - 31 December 2015 - 7:59am

Clive Coleman investigates the statutes that have their origins in the Cold War space race.

What happened to the UK's moon dust?

Astronomy News - 31 December 2015 - 7:58am

Files released by the National Archives shed light on how prime ministers viewed an official souvenir of moon dust that was given to the country by the US.

Dense magnetized plasma associated with a fast radio burst

Astronomy News - 24 December 2015 - 8:53am

Dense magnetized plasma associated with a fast radio burst

Nature 528, 7583 (2015). doi:10.1038/nature15769

Authors: Kiyoshi Masui, Hsiu-Hsien Lin, Jonathan Sievers, Christopher J. Anderson, Tzu-Ching Chang, Xuelei Chen, Apratim Ganguly, Miranda Jarvis, Cheng-Yu Kuo, Yi-Chao Li, Yu-Wei Liao, Maura McLaughlin, Ue-Li Pen, Jeffrey B. Peterson, Alexander Roman, Peter T. Timbie, Tabitha Voytek & Jaswant K. Yadav

Fast radio bursts are bright, unresolved, non-repeating, broadband, millisecond flashes, found primarily at high Galactic latitudes, with dispersion measures much larger than expected for a Galactic source. The inferred all-sky burst rate is comparable to the core-collapse supernova rate out to redshift 0.5. If the observed dispersion measures are assumed to be dominated by the intergalactic medium, the sources are at cosmological distances with redshifts of 0.2 to 1 (refs 10 and 11). These parameters are consistent with a wide range of source models. One fast burst revealed circular polarization of the radio emission, but no linear polarization was detected, and hence no Faraday rotation measure could be determined. Here we report the examination of archival data revealing Faraday rotation in the fast radio burst FRB 110523. Its radio flux and dispersion measure are consistent with values from previously reported bursts and, accounting for a Galactic contribution to the dispersion and using a model of intergalactic electron density, we place the source at a maximum redshift of 0.5. The burst has a much higher rotation measure than expected for this line of sight through the Milky Way and the intergalactic medium, indicating magnetization in the vicinity of the source itself or within a host galaxy. The pulse was scattered by two distinct plasma screens during propagation, which requires either a dense nebula associated with the source or a location within the central region of its host galaxy. The detection in this instance of magnetization and scattering that are both local to the source favours models involving young stellar populations such as magnetars over models involving the mergers of older neutron stars, which are more likely to be located in low-density regions of the host galaxy.

China’s dark-matter satellite launches era of space science

Astronomy News - 24 December 2015 - 8:52am

China’s dark-matter satellite launches era of space science

Nature 528, 7583 (2015).

Authors: Elizabeth Gibney, Celeste Biever & Davide Castelvecchi

Monkey King is first in a line of Chinese space missions focused on scientific discovery.

A dynamic magnetic tension force as the cause of failed solar eruptions

Astronomy News - 24 December 2015 - 8:49am

A dynamic magnetic tension force as the cause of failed solar eruptions

Nature 528, 7583 (2015). doi:10.1038/nature16188

Authors: Clayton E. Myers, Masaaki Yamada, Hantao Ji, Jongsoo Yoo, William Fox, Jonathan Jara-Almonte, Antonia Savcheva & Edward E. DeLuca

Coronal mass ejections are solar eruptions driven by a sudden release of magnetic energy stored in the Sun’s corona. In many cases, this magnetic energy is stored in long-lived, arched structures called magnetic flux ropes. When a flux rope destabilizes, it can either erupt and produce a coronal mass ejection or fail and collapse back towards the Sun. The prevailing belief is that the outcome of a given event is determined by a magnetohydrodynamic force imbalance called the torus instability. This belief is challenged, however, by observations indicating that torus-unstable flux ropes sometimes fail to erupt. This contradiction has not yet been resolved because of a lack of coronal magnetic field measurements and the limitations of idealized numerical modelling. Here we report the results of a laboratory experiment that reveal a previously unknown eruption criterion below which torus-unstable flux ropes fail to erupt. We find that such ‘failed torus’ events occur when the guide magnetic field (that is, the ambient field that runs toroidally along the flux rope) is strong enough to prevent the flux rope from kinking. Under these conditions, the guide field interacts with electric currents in the flux rope to produce a dynamic toroidal field tension force that halts the eruption. This magnetic tension force is missing from existing eruption models, which is why such models cannot explain or predict failed torus events.

VIDEO: Fireball filmed over Nevada and California

Astronomy News - 24 December 2015 - 8:46am

US defence officials confirm a streaking fireball over the skies of Nevada and California was Russian space debris.

Unravelling the Cosmic Web: Survey gives insights into Universe's structure

Astronomy News - 23 December 2015 - 10:20am

Today marks the release of the first papers to result from the XXL survey, the largest survey of galaxy clusters ever undertaken with ESA's XMM-Newton X-ray observatory. The gargantuan clusters of galaxies surveyed are key features of the large-scale structure of the Universe and to better understand them is to better understand this structure and the circumstances that led to its evolution. The first results from the survey, published in a special issue of Astronomy and Astrophysics, hint at the answers and surprises that are captured in this unique bank of data and reveal the true potential of the survey.

Euclid dark Universe mission ready to take shape

Astronomy News - 23 December 2015 - 10:20am

Euclid, ESA's dark Universe mission, has passed its preliminary design review, providing confidence that the spacecraft and its payload can be built. It's time to start 'cutting metal'.

ALMA Reveals Planetary Construction Sites

Astronomy News - 23 December 2015 - 10:19am
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found the clearest indications yet that planets with masses several times that of Jupiter have recently formed in the discs of gas and dust around four young stars. Measurements of the gas around the stars also provide additional clues about the properties of those planets.

Caught in the Act: Hubble Captures First-Ever Predicted Exploding Star

Astronomy News - 23 December 2015 - 10:18am

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Hubble has captured an image of the first-ever predicted supernova explosion. The reappearance of the supernova dubbed "Refsdal" was calculated by different mass models of a galaxy cluster whose immense gravity is warping the supernova's light as the light travels toward Earth. The supernova was previously seen in November 2014 behind the galaxy cluster MACS J1149.5+2223, part of Hubble's Frontier Fields program. Astronomers spotted four separate images of the supernova in a rare arrangement known as an Einstein Cross. This pattern was seen around a galaxy within MACS J1149.5+2223. While the light from the cluster has taken about five billion years to reach us, the supernova itself exploded much earlier, nearly 10 billion light years ago. The detection of Refsdal's reappearance served as a unique opportunity for astronomers to test their models of how mass especially that of mysterious dark matter is distributed within this galaxy cluster.