Continue Reading.

View On WordPress

ASTRONOMERS DETECT BIGGEST EXPLOSION IN THE HISTORY OF THE UNIVERSE Scientists studying a distant galaxy cluster have discovered the biggest explosion seen in the Universe since the Big Bang. The blast came from a supermassive black hole at the Centre of a galaxy hundreds of millions of light-years away. It released five times more energy than the previous record holder. Professor Melanie Johnston-Hollitt, from the Curtin University node of the International Centre for Radio Astronomy Research, said the event was extraordinarily energetic. "We've seen outbursts in the Centres of galaxies before but this one is really, really massive," she said. "And we don't know why it's so big. "But it happened very slowly -- like an explosion in slow motion that took place over hundreds of millions of years." The explosion occurred in the Ophiuchus galaxy cluster, about 390 million light-years from Earth. It was so powerful it punched a cavity in the cluster plasma -- the super-hot gas surrounding the black hole. Lead author of the study Dr Simona Giacintucci, from the Naval Research Laboratory in the United States, said the blast was similar to the 1980 eruption of Mount St. Helens, which ripped the top off the mountain. "The difference is that you could fit 15 Milky Way galaxies in a row into the crater this eruption punched into the cluster's hot gas," she said. Professor Johnston-Hollitt said the cavity in the cluster plasma had been seen previously with X-ray telescopes. But scientists initially dismissed the idea that it could have been caused by an energetic outburst, because it would have been too big. "People were skeptical because the size of outburst," she said. "But it really is that. The Universe is a weird place." The researchers only realised what they had discovered when they looked at the Ophiuchus galaxy cluster with radio telescopes. "The radio data fit inside the X-rays like a hand in a glove," said co-author Dr Maxim Markevitch, from NASA's Goddard Space Flight Center. "This is the clincher that tells us an eruption of unprecedented size occurred here." The discovery was made using four telescopes; NASA's Chandra X-ray Observatory, ESA's XMM-Newton, the Murchison Widefield Array (MWA) in Western Australia and the Giant Metrewave Radio Telescope (GMRT) in India. Professor Johnston-Hollitt, who is the director of the MWA and an expert in galaxy clusters, likened the finding to discovering the first dinosaur bones. "It's a bit like archaeology," she said. "We've been given the tools to dig deeper with low frequency radio telescopes so we should be able to find more outbursts like this now." The finding underscores the importance of studying the Universe at different wavelengths, Professor Johnston-Hollitt said. "Going back and doing a multi-wavelength study has really made the difference here," she said. Professor Johnston-Hollitt said the finding is likely to be the first of many. "We made this discovery with Phase 1 of the MWA, when the telescope had 2048 antennas pointed towards the sky," she said. "We're soon going to be gathering observations with 4096 antennas, which should be ten times more sensitive." "I think that's pretty exciting." TOP IMAGE....This extremely powerful eruption occurred in the Ophiuchus galaxy cluster, which is located about 390 million light years from Earth. Galaxy clusters are the largest structures in the Universe held together by gravity, containing thousands of individual galaxies, dark matter, and hot gas. Credits: X-ray: NASA/CXC/Naval Research Lab/Giacintucci, S.; XMM:ESA/XMM; Radio: NCRA/TIFR/GMRTN; Infrared: 2MASS/UMass/IPAC-Caltech/NASA/NSF CENTRE IMAGE....The Murchison Widefield Array (MWA) is a low frequency radio telescope and is the first of four Square Kilometre Array (SKA) precursors to be completed. LOWER IMAGE....Tile 107, or “the Outlier” as it is known, is one of 256 tiles of this SKA precursor instrumentn located 1.5km from the core of the telescope. Lighting the tile and the ancient landscape is the Moon. Photographed by Pete Wheeler, ICRAR.

2017 Best Timelapse: ‘GLEAM’ by Dr John Goldsmith, Dr Natasha Hurley-Walker and the GLEAM Team "GLEAM: the southern sky in radio and visible light" A unique timelapse movie showing the sky above a ‘tile’ of the Murchison Widefield Array radio telescope, located in outback Western Australia. The ‘normal’ optical sky transitions to a view of the sky at radio wavelengths. The Milky Way is visible as a band across the sky and the dots beyond are some of the 300,000 galaxies observed by the telescope for the GLEAM survey. Credit: Radio image by Dr Natasha Hurley-Walker (ICRAR/Curtin) and the GLEAM Team. MWA tile and landscape by Dr John Goldsmith / Celestial Visions. This timelapse was awarded Best Timelapse at the 2017 Astrofest Astrophotography Exhibition.

GALAXY SURROUNDED BY A HALO OF TRANQUIL GAS Astronomers studying the outskirts of a distant galaxy have discovered that the galaxy sits in a serene ocean of gas. The massive galaxy, which is about four billion light-years from Earth, is surrounded by a halo of gas that is much less dense and less magnetised than expected. The finding was published today in the journal Science. Astrophysicist Associate Professor Jean-Pierre Macquart, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), said gas on the outskirts of galaxies has traditionally been hard to study. "The halo of gas can actually extend out 10 times further than the stars in a galaxy, and can contain a substantial amount of the matter that's in a galaxy," he said. "But it's very difficult to see the gas directly with a telescope." Associate Professor Macquart said this discovery was made using a new technique involving fast radio bursts -- powerful flashes of energy from deep space. "Fast radio bursts come from all over the sky and last for just milliseconds," he said. "They involve incredible energy -- equivalent to the amount released by the Sun in 80 years. We're not sure what causes them, and have only recently been able to pinpoint the galaxies they come from." Associate Professor Macquart said the research team looked at how a single fast radio burst distorted as it travelled five billion light-years through the universe. Along the way, the burst shot through a galaxy's halo of gas, like a lighthouse's beam cutting through the fog. Associate Professor Macquart said the researchers expected the signal from the fast radio burst to be distorted by the galaxy. "If you go out on a hot summer's day, you see the air shimmering, and the trees in the background look distorted because of the temperature and density fluctuations in the air," he said. "That's what we thought would happen, that the signal from the fast radio burst would be completely distorted after passing through the hot atmosphere of the galaxy. But instead of the stormy galactic 'weather' we were expecting, the pulse we observed had travelled through a calm sea of unperturbed gas." The finding suggests that galaxy halos are much more serene than previously thought, with gas that is less turbulent, less dense and less magnetised than expected. One reason astronomers are so interested in galaxy halos is because they can help us understand why material is ejected from galaxies, causing them to stop growing. University of California Professor of Astronomy and Astrophysics J. Xavier Prochaska, who led the research, said halo gas provides a fossil record of these ejection processes. "So our observations can inform theories about how matter is ejected and how magnetic fields are transported from the galaxy," he said. Professor Prochaska said the team now plans to test other galaxies. "Our research appears to reveal something entirely new about galactic halos," he said. "Unless of course, this galaxy happens to be just some weird exception -- and with only one object you can't be sure about that." The research used a fast radio burst that was detected in November by the Australian Square Kilometre Array Pathfinder (ASKAP), in outback Western Australia. The telescope is a precursor to the Square Kilometre Array (SKA), which will be the world's largest radio telescope when it's built in the next decade. The study was led by Professor Xavier Prochaska from the University of California and involved 19 researchers from around the world.

STAR FORMATION MAY BE HALTED BY COLD IONISED HYDROGEN For the first time ionised hydrogen has been detected at the lowest frequency ever towards the centre of our galaxy. The findings originate from a cloud that is both very cold (around -230 degrees Celsius) and also ionised, something that has never been detected before. This discovery may help to explain why stars don’t form as quickly as they theoretically could. Dr. Raymond Oonk (ASTRON/Leiden Observatory/SURFsara) led this study which is published today in MNRAS. He said: “The possible existence of cold ionised gas had been hinted at in previous work, but this is the first time we clearly see it.” Ionisation is an energetic process that strips electrons away from atoms. The atom will become electrically charged and can then be called an ion. This typically happens in gas that is very hot (10,000 degrees Celsius) and where atoms can easily lose their electrons. It was therefore puzzling to discover the ionised hydrogen from very cold gas in this cloud. Normal energy sources, such as photons from massive stars, would not cause this. More exotic energy forms, such as high energy particles created in supernova shockwaves and near black holes, are more likely to be responsible. Dr. Oonk continues: “This discovery shows that the energy needed to ionise hydrogen atoms can penetrate deep into cold clouds. Such cold clouds are believed to be the fuel from which new stars are born. However, in our galaxy we know that the stellar birth rate is very low, much lower than naively expected. Perhaps the energy observed here acts as a stabiliser for cold clouds, thereby preventing them from collapsing on to themselves and forming new stars.” The observation was made with the Engineering Development Array (EDA), a prototype station of the Square Kilometre Array (SKA), the worlds’ largest radio telescope. A/Prof. Randall Wayth (Curtin University/ICRAR) says: “This detection was made possible by the wide bandwidth of the EDA and the extremely radio quiet location of the Murchison Radio-astronomy Observatory. The low frequency portion of the Square Kilometre Array will be built at this location in the coming years, so this excellent result gives us a glimpse of what the SKA will be capable of once it’s built.” The data reduction was led by Emma Alexander (University of Manchester) as part of her summer student internship at ASTRON: “It’s a very exciting time to be coming into radio astronomy, and it was great to work on the first high resolution spectroscopic data from this SKA prototype station. The technologies that are being developed for the SKA, and the science results that come from them, will be a driving force for my generation of radio astronomers.” This work was carried out as a collaboration between the Netherlands Institute for Radio Astronomy (ASTRON), Leiden University, the International Centre for Radio Astronomy Research (ICRAR), University of Manchester and the Square Kilometre Array. IMAGE....A composite image showing our Galaxy, the Milky Way, rising above the Engineering Development Array at the Murchison Radio-astronomy Observatory in Western Australia. The location of the centre of our Galaxy is highlighted alongside the ionized hydrogen (H+) signal detected from this region of sky. The white-blueish light shows the stars making up the Milky Way and the dark patches obscuring this light shows the cold gas that is interspersed between them. Credit: Engineering Development Array image courtesy of ICRAR. Milky Way image courtesy of Sandino Pusta.

The Engineering Development Array The Engineering Development Array (EDA) is a separate telescope designed and built by Curtin University. It is a single field-node of 256 antennas, replicating the proposed antenna layout of the SKA-low field nodes, but using Murchison Widefield Array (MWA) dipole antennas. Data taken from the EDA is compared and correlated against the MWA. As the MWA antennas have already been thoroughly characterised, the EDA helps us understand how a larger group of randomly spread antennas can be expected to perform in the given layout.