An international team, including University of Cambridge scientists, led by Dr Roger Deane from the University of Cape Town, examined six systems thought to contain two supermassive black holes. The team found that one of these contained three supermassive black holes – the tightest trio of black holes detected at such a large distance – with two of them orbiting each other rather like binary stars. The finding suggests that these closely-packed supermassive black holes are far more common than previously thought.

A report of the research is published in this week’s Nature.

Dr Roger Deane from the University of Cape Town said: ‘What remains extraordinary to me is that these black holes, which are at the very extreme of Einstein’s Theory of General Relativity, are orbiting one another at 300 times the speed of sound on Earth. Not only that, but using the combined signals from radio telescopes on four continents we are able to observe this exotic system one third of the way across the Universe. It gives me great excitement as this is just scratching the surface of a long list of discoveries that will be made possible with the Square Kilometre Array (SKA).’

The team used a technique called Very Long Baseline Interferometry (VLBI) to discover the inner two black holes of the triple system. This technique combines the signals from large radio antennas separated by up to 10,000 kilometres to see detail 50 times finer than that possible with the Hubble Space Telescope. The discovery was made with the European VLBI Network, an array of European, Chinese, Russian and South African antennas, as well as the 305 metre Arecibo Observatory in Puerto Rico. Future radio telescopes such as the SKA will be able to measure the gravitational waves from such black hole systems as their orbits decrease.

At this point, very little is actually known about black hole systems that are so close to one another that they emit detectable gravitational waves. According to Prof Matt Jarvis from the Universities of Oxford and the Western Cape, ‘This discovery not only suggests that close-pair black hole systems emitting at radio wavelengths are much more common than previously expected, but also predicts that radio telescopes such as MeerKAT and the African VLBI Network (AVN, a network of antennas across the continent) will directly assist in the detection and understanding of the gravitational wave signal. Further in the future the SKA will allow us to find and study these systems in exquisite detail, and really allow us gain a much better understanding of how black holes shape galaxies over the history of the Universe.’

Dr Keith Grainge of the University of Manchester, an author of the paper, said: ‘This exciting discovery perfectly illustrates the power of the VLBI technique, whose exquisite sharpness of view allows us to see deep into the hearts of distant galaxies. The next generation radio observatory, the SKA, is being designed with VLBI capabilities very much in mind.’

While the VLBI technique was essential to discover the inner two black, the team has also shown that the binary black hole presence can be revealed by much larger scale features. The orbital motion of the black hole is imprinted onto its large jets, twisting them into a helical or corkscrew-like shape. So even though black holes may be so close together that our telescopes cannot tell them apart, their twisted jets may provide easy-to-find pointers to them, much like using a flare to mark your location at sea. This may provide sensitive future telescopes like MeerKAT and the SKA a way to find binary black holes with much greater efficiency.

The discovery of three closely orbiting supermassive black holes in a galaxy more than four billion light years away could help astronomers in the search for gravitational waves: the ‘ripples in spacetime’ predicted by Einstein.

black holegravitational wavesSquare Kilometre ArrayClare RumseyUniversity of OxfordUniversity of Cape TownUniversity of ManchesterDepartment of PhysicsSchool of the Physical SciencesCavendish LaboratoryThis exciting discovery perfectly illustrates the power of the VLBI technique, whose exquisite sharpness of view allows us to see deep into the hearts of distant galaxies.Dr Keith GraingeRoger Deane (large image); NASA Goddard (inset bottom left; modified from original)Helical jets from one supermassive black hole caused by a very closely orbiting companion (see blue dots). The third black hole is part of the system, but farther away and therefore emits relatively straight jets.

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YesNews type: News

Should the Higgs boson have caused our Universe to collapse?

Talk by Robert Hogan at #nam2014, on combining the Higgs boson with the recent #BICEP2 results

http://www.ras.org.uk/news-and-press/2469-should-the-higgs-boson-have-caused-our-universe-to-collapse


Should the Higgs boson have caused our Universe to collapse?
www.ras.org.uk
British cosmologists are puzzled: they predict that the Universe should not have lasted for more than a second. This startling conclusion is the result of combining the latest observations of the sky with the recent discovery of the Higgs boson. Robert Hogan of King's College London (KCL) will present the new research on 24 June at the Royal Astronomical Society's National Astronomy Meeting in Portsmouth.

Astrophysics: A tight duo in a trio of black holes

Nature 511, 7507 (2014). doi:10.1038/nature13511

Authors: Greg Taylor

Tight pairs of supermassive black holes are expected to emit gravitational waves that could give astronomers a new way to explore the cosmos. One relatively tight pair has been discovered within a rare triple system. See Letter p.57

A close-pair binary in a distant triple supermassive black hole system

Nature 511, 7507 (2014). doi:10.1038/nature13454

Authors: R. P. Deane, Z. Paragi, M. J. Jarvis, M. Coriat, G. Bernardi, R. P. Fender, S. Frey, I. Heywood, H.-R. Klöckner, K. Grainge & C. Rumsey

Galaxies are believed to evolve through merging, which should lead to some hosting multiple supermassive black holes. There are four known triple black hole systems, with the closest black hole pair being 2.4 kiloparsecs apart (the third component in this system is at 3 kiloparsecs), which is far from the gravitational sphere of influence (about 100 parsecs for a black hole with mass one billion times that of the Sun). Previous searches for compact black hole systems concluded that they were rare, with the tightest binary system having a separation of 7 parsecs (ref. 10). Here we report observations of a triple black hole system at redshift z = 0.39, with the closest pair separated by about 140 parsecs and significantly more distant from Earth than any other known binary of comparable orbital separation. The effect of the tight pair is to introduce a rotationally symmetric helical modulation on the structure of the large-scale radio jets, which provides a useful way to search for other tight pairs without needing extremely high resolution observations. As we found this tight pair after searching only six galaxies, we conclude that tight pairs are more common than hitherto believed, which is an important observational constraint for low-frequency gravitational wave experiments.

Astronomy: Speedy stars revealed nearby

Nature 510, 7506 (2014). doi:10.1038/510447c

Astronomers have spotted 28 stars that are hurtling through space fast enough to escape the Milky Way's gravitational pull — the biggest set of such stars, and the nearest to Earth, so far identified.A team led by Jing Zhong of the Shanghai Astronomical Observatory,

Astronomers using ESA and NASA high-energy observatories have discovered a tantalising clue that hints at an elusive ingredient of our Universe: dark matter.

A bright galaxy that suddenly went dark was obscured by wind spurting from its central black hole – enhancing our understanding of these distant objects

Previously, as with the longitude problem 300 years earlier for fixing locations on Earth, there was no unified system of reference for calibrating the heavens.

But now, when investigating the atmospheric structure and chemical make-up of stars, astronomers can use a new stellar scale as a ‘ruler’ – making it much easier for them to classify and compare data on star discoveries.

In fact, the work is a critical first step in the Gaia satellite’s mission to map the Milky Way, as the unprecedented levels of stellar data that will result need “consistent stellar parameters”, the same way we need values to measure everything from temperature to time, say astronomers.

The guidelines are free to download and are already being used by the world’s largest astronomy projects. The work has recently been published in the journal Astronomy & Astrophysics. 

The team, including Dr Paula Jofre from the University of Cambridge’s Institute of Astronomy, selected 34 initial ‘benchmark’ stars to represent the different kinds of stellar populations in our galaxy, such as hot stars, cold stars, red giants and dwarfs, as well as stars that cover the different chemical patterns – or ‘metallicity’ – in their spectrum, as this is the “cosmic clock” which allows astronomers to read a star’s age.

This detailed range of information on the 34 stars form the first value set for measuring the millions of stars Gaia aims to catalogue. Many of the benchmark stars can be seen with the human eye, and have been studied for most of human history – dating back to the very first astronomical records from ancient Babylon.          

“We took stars which had been measured a lot so the parameters are very well-known, but needed to be brought to the same scale for the new benchmark - essentially, using the stars we know most about to help measure the stars we know nothing about,” said Jofre. 

“In previous galactic studies, the Sun is used as the standard to show a method is working, along with a few other well-known stars. But I choose this one because it works for my method, you choose a different one for different reasons; data may not match.

“This is the first attempt to cover a wide range of stellar classifications, and do everything from the beginning – methodically and homogenously.”    

Launched at the end of last year, Gaia will gather data on over a billion stars in the Milky Way, allowing astronomers to study for the first time in close detail its myriad stars and planetary systems. Petabytes of data will be sent back to Earth – roughly the equivalent of all the information held in all the libraries of the world today.

The new value system was needed to ensure that analysis of this extraordinary amount of data is done in the most effective and efficient way, a template to measure the vast stream of data against.

Jofre focused on spectroscopic data to work out metallicity: the chemical combination that makes up a star. Just as a raindrop can split sunlight into the colours of the rainbow, spectroscopes split the light from a star into its chemical elements – and the results can be read like a musical score, with high notes or low notes in the scale giving clues as to the star’s age. On average, the higher a star’s metal content the younger it is.

Jofre created a ‘spectral’ library, combining the best data on the atmospheric structure of benchmark stars to determine a uniform scale for metallicity. Together with definitive scales for the stars’ temperatures and surface gravities, produced with colleagues at the University of Uppsala and the University of Bordeaux, her work completes the measuring system that will be used to gauge data from Gaia.

“Now this set of data scales for the benchmark stars can be used as a way of making definitive measurements of others stars – invaluable to astronomers working on a wide range of projects,” Jofre said.

The benchmark stars are already being used as a standardising model by Gaia’s sister project, the Gaia-ESO survey, which is observing stellar spectra at a high resolution from the Very Large Telescope in Chile. They will also provide the basis for the thousands of reference stars needed to set the parameters for the hugely ambitious Gaia satellite once it starts mapping the entire galaxy – the “pillars for the enormous calibrators”.

The fact that the ideal benchmark stars needed to be ones we already have a lot of data on means that many are bright and relatively near to the Earth – and have been the subject of wonder across civilisations.

Aldebaran, Arcturus, Pollux, Procyon and Alpha Centauri have played a part in the culture and mythology of mankind since they were first identified thousands of years ago. Babylonian astronomers used them as a reference point to describe the positions of the moon and planets as they moved through the night sky, appearing in the Babylonian Astronomical Diaries dating back to almost 1000 years BC.

“Many people interested in astronomy know these stars, their position in constellations, and the best time of year to see them. It is amazing that there is still so much to learn about the physics of these most well-known stars," said Dr. Ulrike Heiter from the Uppsala University.

“While stars do move over millennia, for humans they are fixed points – used to navigate the Earth for centuries. We are still using them as fixed points, but this time for navigating the galaxy,” Jofre said.

UK Gaia lead Professor Gerry Gilmore added: “Advances in understanding the history and structure of our Galaxy with ambitious projects are possible only because, like Newton, we see farther by standing on the shoulders of giants. For reliably determining what chemical elements the stars are made of, those giants are the benchmark stars. All our vastly expanding knowledge depends on really understanding the few."

Inset images: Crab Nebula and graphic rendering of the Gaia satellite

A team of astronomers have created the first standardised set of measurement guidelines for analysing and cataloguing stars.

This is the first attempt to cover a wide range of stellar classifications, and do everything from the beginning – methodically and homogenouslyPaula JofreAmanda Smith/Institute of AstronomyThe first standardised way to measure stars has been developed for Gaia mission

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YesNews type: News

Dark matter with a tiny electrical charge could put the brakes on pulsars, offering a new way to look for clues to the nature of the mysterious substance

A (personal) call for a giant space telescope from Martin Barstow. He'll talk about this on Tuesday at the National Astronomy Meeting. http://www.ras.org.uk/news-and-press/news-archive/254-news-2014/2474-time-to-think-big-a-call-for-a-giant-space-telescope


Time to think big: a call for a giant space telescope
www.ras.org.uk
In the nearly 25 years since the launch of the Hubble Space Telescope (HST), astronomers and the public alike have enjoyed ground-breaking views of the cosmos and the suite of scientific discoveries that followed. The successor to HST, the James Webb Space Telescope should launch in 2018 but will have a comparatively short lifetime. Now Prof Martin Barstow of the University of Leicester is looking to the future. In his talk at the National Astronomy Meeting (NAM 2014) in Portsmouth on Tuesday 24 June, he calls for governments and space agencies around the world to back the Advanced Technologies Large Aperture Space Telescope (ATLAST), an instrument that would give scientists a good chance of detecting hints of life on planets around other stars.

The telescope that will live on the now-flat summit of Cerro Amazones in the Atacama desert will be the largest of its kind in the world - and a ghost

Scientists who claimed to have found a pattern in the sky left by the super-rapid expansion of space just fractions of a second after the Big Bang say they are now less confident of their result.

Today a groundbreaking ceremony took place to mark the next major milestone towards ESO’s European Extremely Large Telescope (E-ELT). Part of the 3000-metre peak of Cerro Armazones was blasted away as a step towards levelling the summit in preparation for the construction of the largest optical/infrared telescope in the world.

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Active galaxies host supermassive black holes in their cores. The intense gravity of the black hole creates a turbulent cauldron of extreme physics. These galaxies, such as NGC 5548 in this study, are too far away for the plasma fireworks to be directly imaged. Therefore astronomers use X-ray and ultraviolet spectroscopy to infer what is happening near the black hole. The new twist is the detection of a clumpy stream of gas that has swept in front of the black hole, blocking its radiation. This deep look into a black hole's environment yields clues to the behavior of active galaxies.

Astronomers have discovered strange and unexpected behaviour around the supermassive black hole at the heart of the galaxy NGC 5548. The international team of researchers detected a clumpy gas stream flowing quickly outwards and blocking 90 percent of the X-rays emitted by the black hole. This activity could provide insights into how supermassive black holes interact with their host galaxies.

For the first time, the BICEP2 team – hailed for their gravitational wave discovery earlier this year – have dialled back on the certainty of the result

Cosmic inflation is sound whether or not we have found primordial gravitational waves, says the theory's co-founder Andrei Linde

An international team of astronomers, using data from several NASA and European Space Agency (ESA) space observatories, has discovered unexpected behavior from the supermassive black hole at the heart of the galaxy NGC 5548, located 244.6 million light-years from Earth. This behavior may provide new insights into how supermassive black holes interact with their host galaxies.

They may be little, but they pack a big star-forming punch. New observations from NASA's Hubble Space Telescope show small galaxies, also known as dwarf galaxies, are responsible for forming a large proportion of the universe's stars.

The Rosetta spacecraft is now 165,000km from Comet 67P/Churyumov-Gerasimenko, and closing. Pictures of the 4km-wide ice ball will now get more and more detailed.