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Welcome to the webpages of H.E.S.S., one of the leading observatories studying very high energy (VHE) gamma-ray astrophysics. To learn more about H.E.S.S. and the high energy universe, or to view pictures from the telescopes and the site in Namibia visit the About H.E.S.S. section.

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H.E.S.S. completes a very successful year 2020
February 10, 2021

2020 will have its place in history. The Covid-19 pandemic affected the lives of many people all over the world. That is why we are grateful to the continued efforts of our local crew and shifters, and many members of the collaboration, in keeping H.E.S.S. running during this unprecedented time. Thanks to their hard work, the experiment completed an extremely successful year 2020. We celebrate a record telescope efficiency resulting in the largest annual amount of data taken in the history of H.E.S.S..

2020 has been the first full year in the H.E.S.S. extension phase that started with the installation of a new camera on CT5, the world's largest Imaging Atmospheric Cherenkov Telescope (IACT). For this phase the collaboration had set new goals to increase operational efficiency and agility. While the implementation was challenged by global, Covid-19 induced travel restrictions, the high goals that had been set for H.E.S.S. have been met. Not only did the H.E.S.S. telescopes continue observations throughout the pandemic-stricken year - no small feat. The new camera runs flawlessly. Many new features in operations increased the on-target time. As a result the number of observing hours obtained with all telescopes has increased further and reached a new record level.

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The new camera on the CT5 telescope (shown here after its arrival in Namibia, © C. Föhr, Heidelberg) worked smoothly throughout its first year on site, contributing to the high telescope efficiency.

2020 has been the most successful year in terms of data-taking in the history of H.E.S.S. The operational efficiency exceeded 98% for the full 5 telescope array for most of the year, with an average telescope efficiency of 95%. In the entire year about 1180 hours of dark-time observations were taken with each of the 5 telescopes. This record level is unrelated to weather conditions, which caused weather losses that were close to the long-term average.

In addition, the collaboration started taking data under moonlight conditions, reflecting the increasing importance of time-domain astronomy for the H.E.S.S. science program. This mode is still in its ramp-up phase and is expected to lead to a further increase of observing time in 2021.

The collaboration does not take for granted all the work that has gone into making sure the operations were smooth and successful, but aims for another high in 2021 and is looking forward to again meet in person and celebrate together.

We mourn the passing of our friend and colleague
January 10, 2021
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Friends and colleagues were sad and shocked to learn that on January 9, 2021 Albert Jahnke died in his hometown, Windhoek, in Namibia. Albert, who has joined the local crew of the H.E.S.S. experiment on its Farm Göllschau site in 2006, died of an infection with Covid-19.

The H.E.S.S. Collaboration offers its deepest condolences to the family and friends of Albert Jahnke.

Albert Jahnke graduated from Windhoek and subsequently Technikon in South Africa. He had worked in telecommunication with various schools and enterprises before deciding to combine his profession with his long-standing interest in astronomy. In 2006 he joined the team in charge of operating the H.E.S.S. array on Farm Göllschau. First he was responsible for training the monthly shift-crews of H.E.S.S. members, mostly from Europe, for their four-week observing campaigns. Albert introduced them to the safety regulations, instrumentation and operation of the telescopes and observational procedures and worked alongside with them for the first few nights of the monthly shift. He kept his responsibility for this activity throughout his entire engagement in H.E.S.S. and has worked closely with more than a hundred two-to-three-person shift crews.

Over the years Albert took up other duties, contributed to many installations on the H.E.S.S. site, worked tirelessly on maintaining all hardware components, and cooperated closely with the many teams of the collaboration that are in charge of any subsystem of the array to ensure the proper functioning. He contributed to almost all aspects of local operations. His dedication to H.E.S.S. was outstanding and it has frequently been difficult to prevent him from working overtime well past his term of duty. He was always available to help shift-crews with any problem they might face at any time of the day and often provided advice even from home when being off-duty.

Beyond work in the control-building and with the telescopes, Albert's contribution to life on Göllschau will probably be best remembered for his excellent barbecues. These weekly events were known as highlights in the monthly shifts and very much looked forward to by returning visitors.

Albert enjoyed working for H.E.S.S. and was a devoted, reliable and hard-working colleague who contributed much to the success of the experiment. Following a very difficult year he fell victim to the pandemic during a well-deserved Christmas and New Year break.

He has been a good friend to many members of the collaboration. He will be truly missed.

H.E.S.S. data resolve extragalactic jet in Centaurus A
June 18, 2020

Today the H.E.S.S. collaboration published a breakthrough result in the magazine Nature (Volume 582, pages 356–359, 2020), revealing the gamma-ray emission from the famous radio galaxy Centaurus A (also known as NGC 5128) to be spatially extended over thousands of light-years. This is the first time that an extragalactic source has been spatially resolved in the regime of very high energy gamma-ray astronomy and permits a direct determination of the size the region responsible for gamma-ray emission at TeV energies in an active galaxy. The publication, based on advanced data analysis of a large amount of excellent data obtained with the H.E.S.S. array is a technical achievement and an important step in our understanding of relativistic jets in the Universe.

During the last decades the universe beyond our Milky Way has been probed in the light of very high energy (VHE) gamma-rays, identifying many different kinds of distant Quasars and other active galaxies. Curiously, those distant and extremely luminous sources of gamma-ray emission are very often found to vary within weeks or days - sometimes even as fast as hours. It was hence concluded, that the highly energetic emission originates from very compact regions - very likely linked to a massive Black Hole in the center of the host galaxy. The new study of Centaurus A observations reveals that the emitting regions of these very energetic sources are actually extended over many thousands of light-years.

Centaurus A, one of the first radio galaxies to be discovered, is a well-known active galaxy on the Southern Sky that displays prominent jets in highly resolved radio and X-ray images. The H.E.S.S. array detected TeV gamma-ray radiation from this object in 2009 and studies its spectral and temporal characteristics. A new analysis method that now allows mprphological studies find the gamma-ray source to be spatially extended in the direction of the radio and X-ray jets. While the different angular resolutions that can be achieved in different enrgy ranges prohibit a directs comparison on all angular scales, the figure clearly illustrates that the best-fitting model of the gamma-ray emission lines up with the synchrotron radiation revealed in the radio band.

H.E.S.S. array continues observations during COVID-19 pandemic
May. 10, 2020

While the COVID-19 pandemic has spread around the globe and still imposes severe restrictions in very many countries, the H.E.S.S. array was able to continue operations throughout March and April 2020 and anticipates continuous operations in the forthcoming months. This is very important for scientific investigations within the HESS collaboration and the scientific community at large and is made possible by several favorable circumstances:

The HESS array is located on the Goellschau farm, 120 km south of Windhoek in Namibia, a sparsely populated region in a sparsely populated country. The small local crew and the observers live and work in a very isolated environment already in normal times. Thanks to early and efficient monitoring, Namibia has been able to limit the influx and spread of Corona in the country and suffers very small numbers of infections. The H.E.S.S. site is a very safe place to work and operate. At the same time, Namibian regulations during the pandemic permit the continuation of Scientific Services and thus enabled operations.

The observers that had started their scheduled shift prior to the onset of restrictions have fortunately been able and eager to continue measurements beyond their regular slot, supported by the on-site local H.E.S.S. crew. Advancing further through these difficult times, the H.E.S.S. observing program continues thanks to members of the Namibian H.E.S.S. partner UNAM (University of Namibia), again supported by the local Namibian H.E.S.S. crew. The situation is continuously monitored as the health and safety of everybody involved is of utmost importance.

Continuous observations ensures new scientific discoveries (such as the detections of one of the brightest outbursts yet measured with HESS) in April 2020 and the completion of the test of new instrumentation that has been installed in the end of 2019. The H.E.S.S. collaboration is grateful to all individuals that have made continuous operations and observations possible and continue to do so in the forthcoming times. This includes the local crew in Namibia, shift-teams and many off-site sub-system experts making extra efforts for the operation of the H.E.S.S. array.