Institute of Astronomy

Astronomy News

Tangled threads weave through cosmic oddity [heic1621]

2 December 2016 - 9:08am

New observations from the NASA/ESA Hubble Space Telescope have revealed the intricate structure of the galaxy NGC 4696 in greater detail than ever before. The elliptical galaxy is a beautiful cosmic oddity with a bright core wrapped in system of dark, swirling, thread-like filaments.

Reorientation of Sputnik Planitia implies a subsurface ocean on Pluto

1 December 2016 - 9:29am

Reorientation of Sputnik Planitia implies a subsurface ocean on Pluto

Nature 540, 7631 (2016). doi:10.1038/nature20148

Authors: F. Nimmo, D. P. Hamilton, W. B. McKinnon, P. M. Schenk, R. P. Binzel, C. J. Bierson, R. A. Beyer, J. M. Moore, S. A. Stern, H. A. Weaver, C. B. Olkin, L. A. Young & K. E. Smith

The deep nitrogen-covered basin on Pluto, informally named Sputnik Planitia, is located very close to the longitude of Pluto’s tidal axis and may be an impact feature, by analogy with other large basins in the Solar System. Reorientation of Sputnik Planitia arising from tidal and rotational torques can explain the basin’s present-day location, but requires the feature to be a positive gravity anomaly, despite its negative topography. Here we argue that if Sputnik Planitia did indeed form as a result of an impact and if Pluto possesses a subsurface ocean, the required positive gravity anomaly would naturally result because of shell thinning and ocean uplift, followed by later modest nitrogen deposition. Without a subsurface ocean, a positive gravity anomaly requires an implausibly thick nitrogen layer (exceeding 40 kilometres). To prolong the lifetime of such a subsurface ocean to the present day and to maintain ocean uplift, a rigid, conductive water-ice shell is required. Because nitrogen deposition is latitude-dependent, nitrogen loading and reorientation may have exhibited complex feedbacks.

Observed glacier and volatile distribution on Pluto from atmosphere–topography processes

1 December 2016 - 9:28am

Observed glacier and volatile distribution on Pluto from atmosphere–topography processes

Nature 540, 7631 (2016). doi:10.1038/nature19337

Authors: Tanguy Bertrand & François Forget

Pluto has a variety of surface frosts and landforms as well as a complex atmosphere. There is ongoing geological activity related to the massive Sputnik Planitia glacier, mostly made of nitrogen (N2) ice mixed with solid carbon monoxide and methane, covering the 4-kilometre-deep, 1,000-kilometre-wide basin of Sputnik Planitia near the anti-Charon point. The glacier has been suggested to arise from a source region connected to the deep interior, or from a sink collecting the volatiles released planetwide. Thin deposits of N2 frost, however, were also detected at mid-northern latitudes and methane ice was observed to cover most of Pluto except for the darker, frost-free equatorial regions. Here we report numerical simulations of the evolution of N2, methane and carbon monoxide on Pluto over thousands of years. The model predicts N2 ice accumulation in the deepest low-latitude basin and the threefold increase in atmospheric pressure that has been observed to occur since 1988. This points to atmospheric–topographic processes as the origin of Sputnik Planitia’s N2 glacier. The same simulations also reproduce the observed quantities of volatiles in the atmosphere and show frosts of methane, and sometimes N2, that seasonally cover the mid- and high latitudes, explaining the bright northern polar cap reported in the 1990s and the observed ice distribution in 2015. The model also predicts that most of these seasonal frosts should disappear in the next decade.

Astronomy: A black hole changes its feeding habits

1 December 2016 - 9:28am

Astronomy: A black hole changes its feeding habits

Nature 540, 7631 (2016). doi:10.1038/nature20480

Authors: Stephanie LaMassa

In the 1980s, the gas surrounding a black hole in a nearby galaxy began to emit much more radiation than before. This change has unexpectedly reversed in the past five years, questioning our understanding of these extreme phenomena.

Planetary science: Pluto's telltale heart

1 December 2016 - 9:28am

Planetary science: Pluto's telltale heart

Nature 540, 7631 (2016). doi:10.1038/540042a

Authors: Amy C. Barr

Studies of a large frost-filled basin on Pluto show that this feature altered the dwarf planet's spin axis, driving tectonic activity on its surface, and hint at the presence of a subsurface ocean. See Letters p.86, p.90, p.94 & p.97

The Mystery of Coronal Heating

1 December 2016 - 9:24am
Video Length: 3:35

Observations by NASA's IRIS spacecraft suggest that "heat bombs" are going off in the sun's outer atmosphere, helping to explain why the solar corona is so mysteriously hot.

Read this story

Downloadable Link: The Mystery of Coronal Heating - mp4YouTubeVimeo

LIGO turns back on to hunt for more gravitational waves

1 December 2016 - 9:23am

The premier gravitational wave observatory just turned back on for another six months - and it's expected to catch twice as many black holes as last time

Quantum particles seen distorting light from a neutron star

1 December 2016 - 9:23am

Astronomers have at last observed polarisation of light by virtual particles in a neutron star's magnetic field, a long-expected quantum effect

Saturn mission approaches tour finale

1 December 2016 - 9:21am

The Cassini spacecraft is beginning the end phases of its mission to Saturn that will eventually see it disposed of in the giant planet's atmosphere.

First Signs of Weird Quantum Property of Empty Space?

30 November 2016 - 11:24am
By studying the light emitted from an extraordinarily dense and strongly magnetised neutron star using ESO’s Very Large Telescope, astronomers may have found the first observational indications of a strange quantum effect, first predicted in the 1930s. The polarisation of the observed light suggests that the empty space around the neutron star is subject to a quantum effect known as vacuum birefringence.

Proxima Centauri really does orbit its two bright neighbours

30 November 2016 - 10:59am

After a century of speculation, we now know the little planet-bearing star revolves around Alpha Centauri A and B every 550,000 years

Mars probe returns first pictures

30 November 2016 - 10:58am

The new satellite that Europe and Russia put in orbit at Mars on 19 October has sent back its first images of the planet.

Moon-dust cake mix shows moon may have had water from the start

29 November 2016 - 9:30am

Early moon geology recreated in the lab suggests water was there to begin with, not added later by comets

Corrigendum: Slowly fading super-luminous supernovae that are not pair-instability explosions

24 November 2016 - 9:29am

Corrigendum: Slowly fading super-luminous supernovae that are not pair-instability explosions

Nature 539, 7630 (2016). doi:10.1038/nature19850

Authors: M. Nicholl, S. J. Smartt, A. Jerkstrand, C. Inserra, M. McCrum, R. Kotak, M. Fraser, D. Wright, T.-W. Chen, K. Smith, D. R. Young, S. A. Sim, S. Valenti, D. A. Howell, F. Bresolin, R. P. Kudritzki, J. L. Tonry, M. E. Huber, A. Rest, A. Pastorello, L. Tomasella, E. Cappellaro, S. Benetti, S. Mattila, E. Kankare, T. Kangas, G. Leloudas, J. Sollerman, F. Taddia, E. Berger, R. Chornock, G. Narayan, C. W. Stubbs, R. J. Foley, R. Lunnan, A. Soderberg, N. Sanders, D. Milisavljevic, R. Margutti, R. P. Kirshner, N. Elias-Rosa, A. Morales-Garoffolo, S. Taubenberger, M. T. Botticella, S. Gezari, Y. Urata, S. Rodney, A. G. Riess, D. Scolnic, W. M. Wood-Vasey, W. S. Burgett, K. Chambers, H. A. Flewelling, E. A. Magnier, N. Kaiser, N. Metcalfe, J. Morgan, P. A. Price, W. Sweeney & C. Waters

Nature502, 346–349 (2013); doi:10.1038/nature12569In this Letter, we have identified an important error affecting Fig. 4 and Extended Data Fig. 6, as well as the values of some parameters derived from our model fits. We stress that

Magnetic reversals from planetary dynamo waves

24 November 2016 - 9:29am

Magnetic reversals from planetary dynamo waves

Nature 539, 7630 (2016). doi:10.1038/nature19842

Authors: Andrey Sheyko, Christopher C. Finlay & Andrew Jackson

A striking feature of many natural dynamos is their ability to undergo polarity reversals. The best documented example is Earth’s magnetic field, which has reversed hundreds of times during its history. The origin of geomagnetic polarity reversals lies in a magnetohydrodynamic process that takes place in Earth’s core, but the precise mechanism is debated. The majority of numerical geodynamo simulations that exhibit reversals operate in a regime in which the viscosity of the fluid remains important, and in which the dynamo mechanism primarily involves stretching and twisting of field lines by columnar convection. Here we present an example of another class of reversing-geodynamo model, which operates in a regime of comparatively low viscosity and high magnetic diffusivity. This class does not fit into the paradigm of reversal regimes that are dictated by the value of the local Rossby number (the ratio of advection to Coriolis force). Instead, stretching of the magnetic field by a strong shear in the east–west flow near the imaginary cylinder just touching the inner core and parallel to the axis of rotation is crucial to the reversal mechanism in our models, which involves a process akin to kinematic dynamo waves. Because our results are relevant in a regime of low viscosity and high magnetic diffusivity, and with geophysically appropriate boundary conditions, this form of dynamo wave may also be involved in geomagnetic reversals.

History: Women who read the stars

24 November 2016 - 9:27am

History: Women who read the stars

Nature 539, 7630 (2016). doi:10.1038/539491a

Author: Sue Nelson

Sue Nelson delights in Dava Sobel's account of a rare band of human computers.

Astrophysics: Homing in on a fast radio burst

24 November 2016 - 9:26am

Astrophysics: Homing in on a fast radio burst

Nature 539, 7630 (2016). doi:10.1038/539470b

The origins of powerful, millisecond-long radio pulses from space called fast radio bursts (FRBs) remain a mystery. But researchers studying the brightest FRB seen so far have zeroed in on its location more accurately than ever before.Vikram Ravi at the California Institute of Technology

Hubble rounds up the first worlds we’ll check for alien life

24 November 2016 - 9:24am

The space telescope is set to spend hundreds of hours over the next year picking out the perfect planet for its successor, the James Webb Space Telescope, to probe in earnest

Honour for software writer on Apollo moon mission

24 November 2016 - 9:22am

Barack Obama awards medal to Margaret Hamilton to recognise role in sending humankind into space.

Schiaparelli: Esa gives update on Mars crash investigation

24 November 2016 - 9:22am

The European Space Agency's preliminary report into the Schiaparelli crash on Mars confirms the probe became confused about its altitude.