The extent to which galaxies consume one another has been revealed in research.
Findings from the study help to explain how galaxies such as the Milky Way were formed.
A team of scientists has used a highly sensitive instrument on one of the world’s largest telescopes to witness a dominant galaxy ingesting the stars of its near neighbours.
Deep images
Astronomers took extremely wide-view, long exposures of a nearby group of galaxies known as the M81 Group, which lies 11.7 million light years from the Milky Way.
They observed the dominant central galaxy, M81, capturing stars from its two nearest neighbouring galaxies.
The gravitational pull of M81 was shown to distort the shapes of the other galaxies, pulling their stars into long tails, in a process called tidal stripping.
The images reveal for the first time how the stars from smaller galaxies are being ingested into M81.
It is expected that eventually the smaller galaxies will be devoured entirely.
Growing evidence
The team, including researchers from the University of Edinburgh, were not surprised to see this process taking place.
However, the degree of interaction witnessed exceeded their expectations.
Findings from the study add to two decades of research during which evidence for this process has been mounting.
In the early 1990s, scientists discovered that our own Milky Way is in the process of subsuming a smaller system known as the Sagittarius dwarf galaxy.
The study, to be published in Astrophysical Journal Letters, was conducted using the Hyper Suprime-Cam on the Subaru Telescope in Hawaii.
It was carried out by astronomers from Shanghai Astronomical Observatory, the National Astronomical Observatory of Japan, the Universities of Edinburgh and Cambridge, and Hiroshima University.
"The extremely faint outer regions of galaxies are challenging to study, but our findings reveal that they contain a wealth of information about how galaxies capture and cannibalise their smaller neighbours. This is important for understanding how large galaxies like our Milky Way have formed and evolved over time." Prof. Annette Ferguson, School of Physics and Astronomy
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Astronomers have discovered a planet, likely to be rocky, close to our own solar system.
The planet, which has a three-day orbit round a central star, is joined by a further three planets also newly discovered in the same system. The star at the centre of the system can be seen in the sky close to the Cassiopeia the Queen constellation, near the North Star, and is visible to the naked eye from dark skies.
Future research
At a distance of just 21 light years away, the rocky planet is the nearest confirmed outside our solar system. It is also the closest planet to Earth that has been found to transit across the front of its star which, together with its short orbit, makes it ideal for further study.
The newfound Earth-like planet, designated HD 219134b, was discovered by an international team of astronomers using data from the HARPS-North instrument on the 3.6-metre Telescopio Nazionale Galileo in the Canary Islands. Scientists found that it weighs 4.5 times the mass of Earth, making it what is termed a super-Earth.
"Although this planet is far too hot to be habitable, it is an amazing discovery given how close and bright the star is. This will provide amazing opportunities to learn about and characterise a rocky planet outside our solar system." Dr Eric Lopez, School of Physics & Astronomy, University of Edinburgh
Images from space
Three additional planets in the system were also found - one planet with a mass at least 2.7 times that of the Earth orbits the star once every 6.8 days. A Neptune-like planet with nine times the mass of Earth circles in a 47-day orbit. Much further out from the star, a hefty fourth world with 62 times the mass of Earth orbits at a distance of about 200 million miles, with a year length of 1,190 days.
Astronomers used NASA’s Spitzer Space Telescope to capture the smallest planet crossing in front of the star. The star was seen to dim slightly as the planet crossed its face. Measuring the depth of the transit gave the planet’s size, enabling the team to calculate the planet’s density, which showed that it is a rocky world.
"This is a fascinating system, not only because it is around a relatively nearby star, but also because we are able to determine the compostion of the closest of the four planets, and because the architecture, with three inner low-mass planets with an outer, more massive companion, is similar to that of our own Solar System." Prof. Ken Rice, School of Physics & Astronomy, University of Edinburgh
Transiting planets
Any of the other three planets might also pass directly in front of the star, so the team plans to search for additional transits across the star in the months ahead. The star which the planets orbit is cooler, smaller and less massive than our Sun, and is known as HD 219134.
Transiting planets are ideal targets for astronomers wanting to know more about planetary compositions and atmospheres. As a planet passes in front of its star, it causes the starlight to dim, and telescopes can measure this effect. If molecules are present in the planet's atmosphere, they can absorb certain wavelengths of light, leaving imprints in the starlight. This type of technique will be used in the future to investigate potentially habitable planets and search for signs of life.
The study will be published in the journal Astronomy & Astrophysics.
HARPS-North
The HARPS-North project is led by the University of Geneva, and involves the Universities of St Andrews, Edinburgh and Queen’s University Belfast. Other partners are the Harvard-Smithsonian Center for Astrophysics, and the Italian National Institute for Astrophysics.
The St Andrews and Edinburgh contributions were part-funded by the Scottish Funding Council through the Scottish Universities Physics Alliance. Together with funds from Queen’s University Belfast, these contributions funded construction of the telescope interface and instrument control systems at the Science and Technology Facilities Council’s UK Astronomy Technology Centre in Edinburgh.
The UK Astronomy Technology Centre instrument team were responsible for delivering the HARPS-North instrument Front End Unit, Calibration Unit, Instrument control electronics and software, Detector control system and Sequencer software. In addition they helped to install and commission the instrument on the Telescopio Nazionale Galileo (TNG) in partnership with colleagues from the University of Geneva and the TNG.
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Professor Peter Higgs has been awarded the world’s oldest scientific prize, the Royal Society’s Copley Medal.
The award has been made for the Professor’s work on the theory of the Higgs boson, a fundamental physical particle.
The particle was discovered in experiments at the European Organization for Nuclear Research (CERN) in 2012.
Prof Higgs was awarded a Nobel Prize in Physics 2013 for his research.
Highly ranked peers
"It is an honour to be the recipient this year of the Copley Medal, the Royal Society’s premier award." Professor Peter Higgs, School of Physics & Astronomy
The Copley medal was first awarded by the Royal Society in 1731.
Previous winners include Charles Darwin, Humphrey Davey and Albert Einstein.
It is awarded for outstanding achievements in scientific research.
In recent times it has been awarded to eminent scientists such as theoretical physicist Stephen Hawking, DNA fingerprinting pioneer Alec Jeffreys and discoverer of graphene Andre Geim.
"Peter Higgs is a most deserving winner of the Copley Medal. I congratulate him. His work, alongside that of Francois Englert, has helped shape our fundamental understanding of the world around us. The search for the Higgs boson completely ignited the public’s imagination, hopefully inspiring the next generation of scientists. The Copley Medal is the highest honour the Royal Society can give a scientist and Peter Higgs joins the ranks of the world’s greatest ever scientists." Professor Sir Paul Nurse, President, The Royal Society
The LHCb experiment at CERN’s Large Hadron Collider (LHC) has reported the discovery of resonances in a B-hadron decay that are consistent with particles known as pentaquarks. The collaboration has submitted a paper reporting these findings to the journal Physical Review Letters.
This is an exciting development since, as the name suggests, pentaquarks are particles that are composed of five quarks rather than the typical three-quark combinations that make up protons and neutrons or two-quark combinations that make mesons. Their existence has been predicted for more than 50 years and over that time many different experiments have made claims of their existence. However, these have all eventually been refuted as more data has been collected.
LHCb (Large Hadron Collider beauty) is an experiment set up to explore what happened after the Big Bang that allowed matter to survive and build the Universe we inhabit today. LHCb researchers looked for pentaquark states by examining the decay of a baryon known as Λb (Lambda b) into three other particles, a J/ψ (J-psi), a proton and a charged kaon. Studying the spectrum of masses of the J/ψ and the proton revealed that intermediate states were sometimes involved in their production. These have been named Pc(4450)+ and Pc(4380)+, the former being clearly visible as a peak in the data, with the latter being required to describe the data fully. Where the LHCb result differs from previous experimental results is that they are able to use additional information about the direction of the decaying particles to better understand the system.
“The huge dataset collected by LHCb and the excellent detector performance have allowed this discovery to be made. We tried to use all known processes to explain what we saw in the data but they all fell short. Only by introducing the two pentaquark states were we able to fully describe the processes we measured,” Dr Greig Cowan, STFC research fellow in the particle physics group at the University of Edinburgh and a member of the LHCb collaboration.
Due to the fact that these resonances decay into a J/ψ meson and proton, the researchers know that these new states must be formed of two up quarks, one down quark, one charm quark and one anti-charm quark.
“The quarks could be tightly bound, or they could be loosely bound in a sort of meson-baryon molecule, in which the meson and baryon feel a residual strong force similar to the one binding protons and neutrons to form nuclei,” Prof. Franz Muheim, LHCb group leader at Edinburgh.
More studies will be needed to distinguish between these possibilities, and to see what else these new resonances can teach us. The new data that LHCb will collect in LHC run 2 will allow progress to be made on these questions.
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The School invites expressions of interest from potential applicants for the Royal Society's University Research Fellowship. This scheme provides five years of funding to outstanding researchers to help them build an independent research career.
To be eligible, applicants must have between three and eight years of research experience since their PhD by the closing date of the round on 3rd September 2015. Applicants must be a citizen of the EEA or Switzerland or have a relevant connection to the EEA or Switzerland.
More information can be found on the Royal Society's website: https://royalsociety.org/grants/schemes/university-research/
How to apply
Expressions of interest must include a draft project proposal and a CV. This should be submitted to the School's Research and Finance team at admin-researchandfinance [at] ph.ed.ac.uk by Monday 10th August 2015.
EPCC has launched two novel online courses: Practical Introduction to High Performance Computing and Practical Introduction to Data Science. Both are fully accredited by the University of Edinburgh as Postgraduate Professional Development courses.
High Performance Computing (HPC) and Data Science are increasingly important in solving scientific and commercial problems in numerous disciplines, creating the need for more experts in these areas. EPCC, the supercomputing centre based in the School of Physics & Astronomy, is an internationally-recognised authority in both fields.
Delivered entirely online, the courses are designed to introduce and explore the fundamental concepts of HPC and Data Science through lectures and practical exercises run on real-world systems, eg the UK's national supercomputer ARCHER. Students will be provided with remote access to cutting-edge computing facilities which they will be able to use over the internet from their personal computers.
Designed to be followed flexibly and part-time, the courses should appeal to anyone interested in developing their knowledge of leading-edge computing. The entry requirement is graduate level education in a relevant field or equivalent work experience.
The courses will run for five months from January 2016. The online material (video lectures, exercises, recommended reading etc) will be accompanied by interaction with the EPCC academic team, and with small groups of fellow students, through a variety of different activities and tools such as online tutorials. Enrolled students will be fully matriculated at the University of Edinburgh and have access to all online student services.
Virtual Open Days
We are holding a number of Virtual Open Days to enable potential students to find out more about the courses. The first Virtual Open Day is scheduled for Friday 17th July 2015 at 11:00 am (BST). Anyone interested in either of the courses is welcome to attend.
Links
Practical Introduction to High Performance Computing
New images of deep space are helping shed light on dark matter, the invisible material that accounts for more than 80 per cent of all the matter in the Universe, but is little understood.
The images are the first from an international project that seeks to aid understanding of how much dark matter is contained, and how it is distributed, in groups of galaxies – such as the group that houses the Milky Way. The study is also hoped to improve scientists’ knowledge of how galaxies are formed.
Being able to explain dark matter would represent a major scientific breakthrough.
Researchers analysed images of more than two million galaxies, typically 5.5 billion light years away, and used their results to calculate precise measurements of the influence of dark matter. They examined how light emitted by galaxies is distorted by the pull of gravity as it passes massive clumps of dark matter.
Researchers found that groups of galaxies typically contain 30 times more dark matter than the visible matter seen in stars.
They also showed that the brightest galaxy in each group nearly always sits at the centre of the dark matter clump that surrounds it. This is the clearest demonstration to date of this phenomenon, predicted by theories of galaxy formation.
Their research, known as the Kilo-Degree Survey (KiDS), uses images captured by the VLT Survey Telescope at the European Southern Observatory in Paranal, Chile.
The study, led by Leiden University in the Netherlands, was carried out in collaboration with scientists from the Universities of Edinburgh and Oxford, University College London, Durham University, and from Italy, Germany, and Australia. It is published in The Monthly Notices Of The Royal Astronomical Society.
“These early results in our quest to create a map of dark matter throughout the Universe are encouraging. We are on our way to a better understanding of the mysteries of this elusive substance, thanks to sophisticated telescope technology and the efforts of our international team of scientists.” Dr Catherine Heymans, of the University of Edinburgh’s School of Physics and Astronomy, who co-leads the international team, said:
Dr Massimo Viola of Leiden Observatory in the Netherlands, who led the study, said: “We look forward to making many more discoveries about this most elusive of substances, dark matter, in the months ahead.”
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Edinburgh astronomers have combined the new Oculus Rift virtual reality headset with Stellarium planetarium software to produce an exciting and immersive way to explore the sky.
The system, known as StarsightVR, was demonstrated live at the National Astronomy Meeting in Llandudno, and will soon be available as a shared group experience to anyone with a headset and an Internet connection.
PhD researcher Alastair Bruce and his supervisor Prof. Andy Lawrence adapted the Stellarium software to create StarsightVR. Bruce saw potential for the Oculus Rift headset, which is expected to be popular in the gaming industry when it goes on sale in 2016, to be adapted for use by astronomy enthusiasts. A prototype version of the system was well received by audiences during a preview at the Edinburgh International Science Festival.
"I have always loved showing the stars to people, but now I can guarantee perfect cloudless skies, and show the universe to people all round the world, while they stay in the comfort of their own homes. Some people are also simply unable to come to places like the Royal Observatory in Edinburgh or to travel to dark skies, so this technology could help them enjoy astronomy in a way that until now wasn’t possible.” Alastair Bruce, StarsightVR project leader
Online sessions
The team will very soon release a beta test version of Stellarium. This means that anybody with an Oculus Rift headset will be able to download the new software and try it out for themselves. But they see this as just the start. "We have a clear idea of the next steps in development - the things we want to add or make better before an official release - but unfortunately we have now run out of money," said Lawrence.
As well as releasing the new software and adding features to the code, Bruce and Lawrence want to use the system to run presenter-led group stargazing sessions live over the Internet. The team built changes into Stellarium so that their central version can send information to remote versions. The idea is that each user will listen to the astronomer-presenter over an audio link, while the presenter points where they need to look, adjusts day/night settings, switches constellation guiding lines on and off, and so on.
"It works beautifully. You feel like you are really outside looking at the starry sky, but it’s even better. You can see fainter stars, speed up the rotation of Earth, look at deep sky objects, and even take the ground away so you feel like you are seeing the stars from space." Prof. Andy Lawrence
The trial shows will be run through the Royal Observatory Edinburgh Trust, a charitable organisation that supports heritage and public interest in astronomy.
Links
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New work by the School of Physics & Astronomy increases our understanding of the atmosphere and chemistry of celestial objects.
The matter that makes up distant planets and even-more-distant stars exists under extreme pressure and temperature conditions. This matter includes a family of seven elements called the noble gases, some of which, such as helium and neon, are household names.
New work from the School of Physics & Astronomy used laboratory techniques to mimic stellar and planetary interiors in order to better understand how noble gases helium and neon control the atmospheres and internal chemistry of these celestial objects. Their work is published by Proceedings of the National Academy of Sciences.
The team used a diamond-anvil cell to bring the noble gases helium, neon, argon, and xenon to more than 500,000 times the pressure of Earth's atmosphere (50 gigapascals), and used a laser to heat them to temperatures ranging up to 28,000 degrees Celcius.
The gases are called “noble” due to a kind of chemical aloofness; they normally do not combine, or “react,” with other elements. Of particular interest were changes in the gases’ ability to conduct electricity as the pressure and temperature changed, because this can provide important information about the ways that the noble gases do actually interact with other materials in the extreme conditions of planetary interiors and stellar atmospheres.
Insulators are materials that are unable to conduct the flow of electrons that make up an electric current. Conductors, or metals, are materials that allow an electric current. Noble gases are not normally conductive at ambient pressures, but this study found that conductivity can be induced under higher pressures.
The researchers found that helium, neon, argon, and xenon transform from visually transparent insulators to visually opaque conductors at extreme conditions that mimic the interiors of different stars and planets.
This has several exciting implications for how noble gases behave in the atmospheres and interiors of planets and stars.
For example, it could help solve the mystery of why Saturn emits more heat from its interior than would be expected given its age. This is tied to the ability, or inability, of the noble gases to be dissolved in liquid metallic hydrogen, the main constituent of gas giant planets such as Saturn and Jupiter.
In Jupiter and Saturn, helium would be insulating near the surface and turn metal-like at depths close to both planets' cores. This change from insulator to metal is expected to allow helium to dissolve in hydrogen near the planets' rocky cores.
However, a difference was observed in the behaviour of neon between the laboratory conditions mimicking the two gas giants. The team’s results indicate that neon would remain an insulator even in Saturn’s core. As such, an ocean-like envelope of undissolved neon could collect deep within the planet and prevent the erosion of Saturn’s core compared to its neighbour Jupiter, where core materials, such as iron, would be dissolving into the surrounding liquid hydrogen.
This lack of core erosion could potentially explain why Saturn is giving off so much internal heat compared to its neighbour Jupiter. Erosion of a planet's core leads to planetary cooling as dense matter is raised upward, whereas in Saturn denser material is allowed to collect at the centre of the planet, producing hotter conditions. These findings could provide the key to solving the longstanding mystery of Saturn's internal heat.
"A tiny ocean of neon forming inside Saturn could have a surprising influence on this planet's evolution. Another tiny planetary feature that has big effects is Earth's ocean: despite making up just a fraction of a percent of the planet's total diameter, Earth's ocean plays a remarkable role in controlling the Earth system, for example by allowing mixing of the Earth's exterior and interior. In Saturn an ocean composed of noble gas instead of water could instead prevent mixing of the planet's interior and exterior. This may solve an old mystery as to why Saturn and its larger neighbour, Jupiter, look so different." Stewart McWilliams, the study's lead author.
Another implication of the team’s findings involves white dwarf stars, which are the collapsed remnants of once-larger stars, having about the mass of our Sun. They are very compact, but have faint luminosities as they give off residual heat. Dense helium is known to exist in the atmospheres of white dwarf stars and may form the surface atmosphere of some of these celestial bodies. The conditions simulated by the team’s laser-heated diamond-anvil cell indicate that this stellar helium should be more opaque (and conducting) than previously expected and this opacity could slow the cooling rates of helium-rich white dwarfs, as well as affect their colour.
Paper abstract
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Fresh theoretical understanding of the behaviour of turbulent plasmas could inform potential applications, from tokamak fusion reactors to new understanding of magnetic fields in cosmology. Researchers at the School of Physics & Astronomy have developed a new mathematical description of the energy flow of a turbulent plasma, and how the loss of energy from a plasma can be controlled.
The study, led by Prof. Arjun Berera and PhD student Moritz Linkmann using the ARCHER supercomputer, has led to the first simplified formula to quantify these effects in plasmas affected by magnetic fields. The work also offers new insights into energy flows between fluids and magnetic systems, aiding understanding of how magnetic energy can grow at large scales in a plasma.
Novel insights into turbulent plasma
Recent work at the School of Physics and Astronomy has added novel insights into how the growth, flow and decay of energy in a turbulent plasma can be controlled by the plasma viscosity, the state of magnetic helicity (internal angular momentum and degree of tangledness of the magnetic field) and the state of cross helicity (correlation between the magnetic field fluctuations and the fluctuations of kinetic energy inherent in a turbulent plasma).
A new formula is obtained for understanding the flow of energy out of, and therefore the energy maintained in, a turbulent plasma, which depends on the state of magnetic and cross helicities contained in the magnetic field-fluid system. These results, obtained by a combination of theoretical work and numerical simulations using the ARCHER supercomputer, show how this energy flow can be controlled, leading to the first simplified formula to quantify these effects in magnetofluids. Understanding has also been obtained in how energy flows between the fluid and the magnetic field, adding new insights on how magnetic energy can grow at large length scales in a turbulent magnetofluid. These theoretical results are fundamental steps towards potential practical applications in areas as varied as controlling the plasma in a tokamak fusion reactor and understanding the presence and growth of magnetic fields in galaxies, galaxy clusters and even at the scale of the entire Universe.
This work has come out in a Physical Review Letter and an earlier Physical Review E Rapid Communication. Both figures below contain results from the two publications, all obtained from medium to high resolution simulations carried out on ARCHER.
Results shown in Fig.1 extend the accuracy and extent of detail from previous results in the literature, while results shown in Fig. 2 had been anticipated in terms of qualitative expectations but were never studied systematically before. Their papers have in turn proposed a new way of looking at the problem and by doing so obtained a simple expression derived from the underlying equations that can predict and explain the behaviour seen in these figures, which is the main significant new advance from this work. Their systematic studies have been made possible to a large extent through access to ARCHER, which enabled them to probe a significant section of parameter space.
It has been known for some time that certain correlations between the velocity and magnetic vector fields alter the dynamics of turbulent magnetofluids. What is new from our work is it predicts with a simple expression how the flow of energy out of a turbulent plasma can be controlled based on the viscosity and state of angular momemtum in the magnetic-fluid system. This is a fundamental step toward potential practical applications in areas as varied as controlling the plasma in a tokamak fusion reactor, understanding the presence and growth of magnetic fields in galaxies, galaxy clusters and even at the scale of the entire Universe.'' Arjun Berera
"Much work still needs to be done before quantitative theoretical predictions can be made. Our results are fundamental in the sense that they apply to turbulent magnetofluids far from the boundaries of a containing vessel. Therefore this does not give the full details for specific geometries, such as of a fusion reactor, but our results describe the general behaviour of evolution of the plasma far away from any boundaries, thus are of general applicability to a range of plasmas systems.'' Moritz Linkmann
This work has been published in a Physical Review Letter and an earlier Physical Review E Rapid Communication:
"Magnetic helicity and the evolution of decaying magnetohydrodynamic turbulence"
Arjun Berera and Moritz Linkmann
Phys. Rev. E 90, Rapid Communication, 041003(R) – Published 22 October 2014
https://journals.aps.org/pre/abstract/10.1103/PhysRevE.90.041003
"Nonuniversality and Finite Dissipation in Decaying Magnetohydrodynamic Turbulence"
M. F. Linkmann, A. Berera, W. D. McComb, and M. E. McKay
Physical Review Letters 114, 235001 (2015) – Published 11 June 2015
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.235001
