In the latest discovery, the H.E.S.S. (a telescope that is operated by an international collaboration of scientists) has found three extremely luminous gamma-ray sources in the Large Magellanic Cloud (LMC), a satellite dwarf galaxy of the Milky Way.
These are objects of different types, namely the most powerful pulsar wind nebula; the most powerful supernova remnant; and a shell of 270 light years in diameter blown by multiple stars, and supernovae – a so-called superbubble.
The discovery is announced in the latest edition of the scientific journal, Science, in a research paper titled: The exceptionally powerful TeV ƴ-ray emitters in the Large Magellanic Cloud, which was published on Friday, 23 January 2015.
“This is a very important breakthrough for the team,” says Professor Sergio Colafrancesco, DST/NRF SKA Research Chair in the Wits School of Physics. “It paves the way to study external galaxies with very high-E telescopes such as H.E.S.S and then later with the planned Cherenkov Telescope Array (CTA) in Namibia. It will lead us to re-examine galaxy evolution and answer questions such as how high-E particles can affect the evolution of cosmic structures in the universe, principally galaxies, and the life cycles of matter in galaxies,” he adds.
Very high-energy gamma rays are the best tracers of cosmic accelerators such as supernova remnants and pulsar wind nebulae – end-products of massive stars. There, charged particles are accelerated to extreme velocities. When these particles encounter light or gas in and around the cosmic accelerators, they emit gamma rays. Very high-energy gamma rays can be measured on Earth by observing the Cherenkov light emitted from the particle showers produced by incident gamma rays high up in the atmosphere using large telescopes with fast cameras.
The Large Magellanic Cloud (LMC) is a dwarf satellite galaxy of our Milky Way, located about 170.000 light years away and showing us its face. New, massive stars are formed at a high rate in the LMC, and it harbors numerous massive stellar clusters. The LMC’s supernova rate relative to its stellar mass is five times that of our Galaxy. The youngest supernova remnant in the local group of galaxies, SN 1987A, is also a member of the LMC. Therefore, the H.E.S.S. scientists dedicated significant observation to searching for very high-energy gamma rays from this cosmic object.
For a total of 210 hours, H.E.S.S. has observed the largest star-forming region within the LMC called Tarantula Nebula. For the first time in a galaxy outside the Milky Way, individual sources of very high-energy gamma rays could be resolved: three extremely energetic objects of different types.
The so-called superbubble 30 Dor C is the largest known X-ray-emitting shell and appears to have been created by several supernovae and strong stellar winds. Superbubbles are broadly discussed as (complementary or alternative to individual supernova remnants) factories where the galactic cosmic rays are produced. The H.E.S.S. results demonstrate that the bubble is a source of, and filled by, highly energetic particles. The superbubble represents a new class of sources in the very high-energy regime.
Pulsars are highly magnetized, fast rotating neutron stars that emit a wind of ultra-relativistic particles forming a nebula. The most famous one is the Crab Nebula, one of the brightest sources in the high-energy gamma-ray sky. The pulsar PSR J0537−6910 driving the wind nebula N 157B discovered by the H.E.S.S. telescopes in the LMC is in many respects a twin of the very powerful Crab pulsar in our own Galaxy. However, its pulsar wind nebula N 157B outshines the Crab Nebula by an order of magnitude, in very high-energy gamma rays. Reasons are the lower magnetic field in N 157B and the intense starlight from neighboring star-forming regions, which both promote the generation of high-energy gamma rays.
The supernova remnant N 132D, known as a bright object in the radio and infrared bands, appears to be one of the oldest – and strongest – supernova remnants still glowing in very high-energy gamma rays. Between 2500 and 6000 years old – an age where models predict that the supernova explosion front has slowed down and it ought no longer to be efficiently accelerating particles – it still outshines the strongest supernova remnants in our Galaxy. The observations confirm suspicions raised by other H.E.S.S. observations, that supernova remnants can be much more luminous than thought before.
Observed at the limits of detectability, and partially overlapping with each other, these new sources challenged the H.E.S.S. scientists. The discoveries were only possible due to the development of advanced methods of interpreting the Cherenkov images captured by the telescopes, improving in particular the precision with which gamma-ray directions can be determined.
Indeed, the new H.E.S.S. II 28 m telescope will boost the performance of the H.E.S.S. telescope system, and in the more distant future the planned Cherenkov Telescope Array (CTA) will provide even deeper and higher-resolution gamma-ray images of the LMC – in the plans for science with CTA, the satellite galaxy is already identified as a “Key Science Project” deserving special attention.
· The H.E.S.S. telescope is operated by an international collaboration of scientists with a strong involvement by South African universities, in particular Wits University, North West University, and the Universities of the Free State and Johannesburg. Wits physicists are particularly involved in data analysis techniques, the development of theoretical interpretation tools of both extragalactic and galactic sources, and in the operational shifts at the telescope location in Namibia.
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Big bites from Apple
Apple’s announcement advanced medical features on its new Apple Watch and a more affordable iPhone were the biggest bites from its annual product launch, writes BRYAN TURNER.
Apple’s annual early-September event kicked off with a small advance that could make a big difference: the next iteration of the Apple Watch, Series 4, with the first consumer-facing ECG monitor approved by authorities. While the overall design remains similar to its predecessors, the screen is around 30% larger than the previous version, thanks to a smaller bezel. This resulted in new categories, namely 40mm and 44mm instead of 38mm and 42mm. However, Apple Watch bands from previous generations still work with the new Apple Watch. The screen is also rounded at the corners of the display, instead of being a square display inside rounded glass. Despite all the improvements, it still weighs around 30 grams without the watch band.
The introduction of the first consumer-facing wrist ECG (electrocardiogram) is revolutionary in the wearable space and reaffirms the Apple Watch as a device for the health conscious. The Apple Watch underwent a full internal and external redesign. Internally, the digital crown has been redesigned to be more “clicky”, with haptic feedback, and features a metal tip for use in an ECG measurement. An ECG can be taken when the user completes a circuit by placing the opposite hand’s finger on the metal tip of the digital crown. This is helpful for those who need to know when they are experiencing atrial fibrillation, an irregular beating of the heart. Fall detection has also been implemented, where a user must tap “I’m fine” after a fall, slip or trip. If the Apple Watch is still for a minute after a fall, emergency contacts are notified with a fall message and location.
Next up, the iPhone line was given an update instead of an upgrade with the iPhone XS. Last year broke the 8-year “major iPhone version followed by an S version” cycle. Apple opted to skip what would have been the iPhone 7S and released the iPhone 8. Apple also released the iPhone X for its tenth anniversary of releasing iPhones. This year, the S cycle is back. The iPhone XS sends the message that Apple is not currently concerned with cosmetic features and would rather focus on making its flagship smartphones better internally.
The iPhone XS was released in 2 tiers, namely the 5.8″ iPhone XS and the 6.5″ iPhone XS Max. The iPhone XS Max is what we know as the “Plus” range, which features a screen that’s almost an inch bigger diagonally than the iPhone XS and holds the same Super Retina Display specification, around 450 pixels per inch. Internally, the iPhone XS Max is no different from the iPhone XS apart from a larger battery.
Apple’s A12 bionic chip is not the first 7-nanometre chip to be announced in a smartphone (that was Huawei) but will be the first to reach the market. The incredible aspect of the 7nm chip is that it houses 6.9 billion transistors, which allow for 5 trillion operations to be run per second. In addition to this, a Neural Engine allocates all the processes where they fit best, either to the CPU, the GPU or processes quickly itself. This speeds the iPhone XS up by 30% compared to the iPhone X – if you are able to notice such things.
Talking pf which, thanks to the better processor, Face ID performs a lot faster. The neural engine can separate hair from the backgrounds of portrait photos. The XS also has wider stereo sound, thanks to a slight internal speaker readjustment. The screen has been optimised for Dolby Vision and HDR10 which work with the OLED screen to provide vibrant colours and distinct on-screen graphics.
Apple left a surprise for the end of its keynote when CEO Tim Cook introduced the iPhone XR. This iPhone looks and feels like an iPhone XS at first glance, but has been stripped of some features.
It’s interesting that Apple is not repeating its iPhone 5C mistakes with this iPhone. It uses the A12 Bionic, the same processor in the XS line, which means that the cheaper iPhone performs exactly the same as the most expensive one. The XR has an edge-to-edge display with Face ID, like the iPhone XS, but has an LCD screen instead of OLED. This would have reduced Apple’s cost per unitsubstantially. On the back, the XR sports a single camera instead of the dual camera setup in the iPhone XS. However, the iPhone XR can still do portrait mode photos, thanks to the A12 Bionic.
Overall, it may seem as if the Apple Watch stole the show, but Apple no doubt hopes the iPhone XR will convince the market it is an affordable iPhone.
IFA: New smartphones and TVs from Hisense
At the recently held IFA in Berlin, Hisense introduced three new smartphones and three TVs.
Hisense provided the following information:
Among the phones unveiled at the event was the new Hisense A6, which comes equipped with two screens – one in the front and one in the back. The front screen features a bright and 6.01 inch FHD+ AMOLED display, while the one on the back has a 5.61 inch HD+ e-ink display with eye-care front light – ideal for reading e-books and performing tasks that do not need a colour display, like energy efficient internet browsing. The phone also combines a 12MP rear camera with a 16MP front camera for serious selfie fun.
Elegantly designed with 3D glass on the back and curved on four sides for a comfortable grip, the Hisense Infinity H12 Pro has an 84 inch X-Infinity Display and a Full HD+ resolution of 1080 x 2280. It is also decked out with a dual camera, offering 12MP and 5MP rear cameras as well as a 20MP front camera with multiple shooting modes including night, indoor, snow, smiling face and panorama modes. For security, the phone can be unlocked using fingerprint identification and Face Unlock.
With a 6.19 inch HD+ X-Infinity Display, for maximum comfort while watching series or playing games on the go, the Hisense Infinity H12 is also the ideal phone for amateur photographers thanks to its dual camera with a 12MP Big Pixel and a secondary 5MP sensor. Other features include 4GB RAM and 32GB ROM which can be extended with MicroSD cards with a capacity of up to 128GB.
Visitors to IFA Berlin got to see Hisense’s new 75 inch U9D TV. Its 4K Quantum Dot Display, which is divided into over 5,000 local dimming zones, combined with premium backlighting (Prime Array Backlight), produces exquisite images with very deep black and bright white for an exceptional viewing experience. The U9D also has a contrast ratio of 150,000:1 and a luminance of 2,500 nits to deliver brilliant and colourful images with high-contrast that almost seem real.
Equally as impressive is the U8A which, with its Elite Backlight technology, delivers brilliant contrast values and images in a wide colour spectrum. The frameless and super slim TV also features a 4K-Quantum Dot-Display with a 120 Hz refresh rate.
Hisense introduced three of its new 4K Laser-TV models at IFA Berlin which give customers a home cinema experience thanks to their massive screens that range from 80 to 100 inches. These connect wirelessly to a console that receives, processes and displays broadcast signals via an integrated TV tuner and delivers streaming content thanks to its Smart TV platform. These TVs can be used in all lighting conditions and offer an image brightness of up to 3,000 lumens.
All of the TVs feature a smart VIDAA U user interface that can be easily personalised – giving viewers extra fast access to their preferred TV station or films from their favourite streaming service. It also comes with a remote control for easy use.