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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Win a Poster Heater with Gadget and Takealot.com
This winter Gadget and Takealot.com are giving away three Poster Heaters, which look like posters but become heaters when you plug them in.
Three Gadget readers will each win a unit, valued at R550 each. To enter, follow @GadgetZA and @Takealot on Twitter and tell us on the @GadgetZA account how many Watts the heater consumes.
What’s the big deal about these heaters? Many of us are struggling to keep the balance between soaring electricity costs and the need to keep warm this winter.
However, the recently launched Poster Heater by EasyHeat and distributed in South Africa by Takealot.com is not only one of the most cost effective electric heaters currently on the market, it is also easy to setup and use.
As the name indicates, it is a poster similar to one you would hang on a wall. But, plug it in and it turns into a 300 Watt heater. The Poster Heater isn’t designed to heat hallways or large rooms, but rather smaller ones like a bedroom or a baby’s nursery or a dressing room.
It uses radiant heating, which means that it heats up in a couple of minutes and the heat is directed at the objects or people around it, quickly taking the chill out of the air and providing a comfortable ambient temperature.
The other advantage of radiant heating is that it doesn’t dry out the air like infrared or gas heaters. Users also don’t have to worry about their children or pets getting too close to it because, even though it gets hot, it can be touched.
To enter the competition follow the steps below:
Competition entry details:
3. The competition closes on 31 July 2018.
4. Winners will be notified via Twitter on 1 August and Takealot.com will be in touch to organise delivery.
5. The competition is only open to South African residents.
Teraco pumps R1bn into SA data centre expansion
Teraco has announced that it will be expanding its Isando Campus to cater for the increased demand for additional data centre capacity.
The expansion will occur in two phases. Phase 1, currently underway, will grow the facility by 2 000 cabinets bringing the total JB1 Campus capacity to 5 700. Total usable floor space will increase by 4 000 square meters, expanding to a total of 12 000 square meters across the data centre campus. The anticipated ready for service date is in Q3 2019.
A total of 60MW of power will be reticulated to the site addressing requirements for further expansion after Phase 1 has been completed. The total power available to the Isando Campus will now reach 80MW.
Jan Hnizdo, Chief Financial Officer, Teraco says that he sees continued demand for Teraco’s services given the unique business model and secular growth trends as the African continent continues to digitally transform. The Teraco Campus expansion follows on from the recently launched Riverfields hyperscale data centre facility in Bredell.
Hnizdo says that funding for the build is via a combination of internally generated funds and enlarging existing debt facilities from R1.2bn to R1.8bn: “Our debt funding partners, Absa, continue to be highly supportive of our business model and are key partners in Teraco’s growth strategy”.
Teraco’s offering to clients of resilient data centre facilities allows for a choice of over 200 telco’s providing connectivity to Africa and the lowest latency interconnection points to cloud and content. Hnizdo says that with the recent announcements of direct interconnection availability to the major cloud onramps such as Amazon Web Services Direct Connect and Microsoft Azure ExpressRoute, Teraco has seen a growing uptake driven by the enterprise market: “The Teraco platform allows enterprises to have direct private connections to all the leading cloud providers in the most latency efficient and resilient manner possible. Enterprises can deploy their public, private and hybrid cloud strategies from the Teraco platform, which allows for complete freedom of choice from a cloud provider perspective, as well as significantly reducing the time and cost for enterprises to access these cloud platforms”.
Over the past decade, Teraco has focused on growing its ecosystems of telco, content, financial services, enterprise and service providers. Its offering is underpinned by providing clients with direct access to Africa’s largest Internet exchange, NAPAfrica, which includes all the benefits of interconnection via the Teraco platform.
Hnizdo says that Teraco is committed to growing its capacity footprint across its core hubs, thereby ensuring that clients have certainty and the flexibility of expansion to take part in the digital transformation that is happening across sub-Saharan Africa: “Teraco continues to invest significantly into the region’s ICT infrastructure and has built, what is now, Africa’s largest data centre. We take pride in our vendor neutral offering, with open access to interconnection and world class resilient data centre infrastructure for all our clients”.