18. June 2019

eROSI­TA – the hunt for Dark En­er­gy be­gins

Proton launcher carrying SRG and eROSITA
Pro­ton launch­er car­ry­ing SRG and eROSI­TA
Image 1/4, Credit: MPE/Vadim Burwitz

Proton launcher carrying SRG and eROSITA

On 13 Ju­ly 2019, at 14:31 CEST, a Pro­ton launch­er car­ry­ing the Spek­trum-Rönt­gen-Gam­ma (SRG) space­craft, the Ger­man X-ray tele­scope eROSI­TA and its Rus­sian part­ner in­stru­ment ART-XC suc­cess­ful­ly lift­ed off from Baikonur Cos­mod­rome in Kaza­khstan.
Spektrum-Röntgen-Gamma is ready for launch
Spek­trum-Rönt­gen-Gam­ma is ready for launch
Image 2/4, Credit: Roscosmos/DLR/SRG/Lavochkin

Spektrum-Röntgen-Gamma is ready for launch

The Ger­man X-ray tele­scope eROSI­TA and its Rus­sian part­ner in­stru­ment ART-XC are in­stalled on the Nav­i­ga­tor plat­form. The Nav­i­ga­tor plat­form sup­plies the Spek­trum-Rönt­gen-Gam­ma space­craft with pow­er, sends the col­lect­ed da­ta to Earth and pro­vides at­ti­tude and or­bit con­trol.      
eROSITA mirror module
eROSI­TA mir­ror mod­ule
Image 3/4, Credit: P. Friedrich/MPE

eROSITA mirror module

The first core com­po­nent of the eROSI­TA space tele­scope con­sists of sev­en iden­ti­cal mir­ror mod­ules aligned in par­al­lel. Each has a di­am­e­ter of 36 cen­time­tres and con­sists of 54 nest­ed mir­ror shells whose sur­face is com­posed of a paraboloid and a hy­per­boloid (Wolter I op­tics). They col­lect high-en­er­gy pho­tons and fo­cus them on­to the X-ray cam­eras.      
eROSITA cameras
eROSI­TA cam­eras
Image 4/4, Credit: P. Friedrich/MPE

eROSITA cameras

The sec­ond core com­po­nent of the tele­scope is the X-ray cam­era sys­tem. At the fo­cal point of each mir­ror sys­tem is a high­ly sen­si­tive CCD de­tec­tor that was spe­cial­ly de­vel­oped for eROSI­TA in the semi­con­duc­tor lab­o­ra­to­ry at the Max Planck So­ci­ety. These de­tec­tors are a fur­ther de­vel­op­ment of ex­ist­ing X-ray CCD cam­eras.      
  • On 13 July 2019, the Spektrum-Röntgen-Gamma (SRG) spacecraft with the German X-ray telescope eROSITA will set off for the second Lagrange point.
  • With its seven X-ray detectors, the German space telescope will observe the entire sky, search for hot sources and map them.
  • eROSITA will help solve the mystery of Dark Energy.
  • Focus: Space

+++ The Spektrum-Röntgen-Gamma (SRG) spacecraft with the German X-ray telescope eROSITA and its Russian partner instrument ART-XC successfully launched from Baikonur Cosmodrome on 13 July 2019 at 14:31 CEST (17:31 local time) on board a Proton rocket. +++

On 13 July 2019 the Spektrum-Röntgen-Gamma (Spektr-RG / SRG) spacecraft will be launched from the Kazakh steppe, marking the start of an exciting journey. SRG will be carrying the German ‘extended ROentgen Survey with an Imaging Telescope Array’ (eROSITA) X-ray telescope and its Russian ART-XC partner instrument. A Proton rocket will carry the spacecraft from the Baikonur Cosmodrome towards its destination – the second Lagrange point of the Sun-Earth system, L2, which is 1.5 million kilometres from Earth. In orbit around this equilibrium point, eROSITA will embark upon the largest ever survey of the hot Universe. The space telescope will use its seven X-ray detectors to observe the entire sky and search for and map hot sources such as galaxy clusters, active black holes, supernova remnants, X-ray binaries and neutron stars. “eROSITA’s X-ray ‘eyes’ are the best that have ever been launched as part of a space telescope. Their unique combination of light-collecting area, field-of-view and resolution makes them approximately 20 times more sensitive than the ROSAT telescope that flew to space in the 1990s. ROSAT also incorporated advanced technology that was ‘made in Germany’. With its enhanced capabilities, eROSITA will help researchers gain a better understanding of the structure and development of the Universe, and also contribute towards investigations into the mystery of Dark Energy,” says Walther Pelzer, Executive Board Member for the Space Administration at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR), which supported the development of eROSITA at the Max Planck Institute for Extraterrestrial Physics (MPE).

Dark Energy – a ‘cosmic fuel’ that is accelerating the expansion of the Universe

The Universe has been expanding continuously since the Big Bang. Until the 1990s, it was thought that this cosmic expansion would slow down and eventually come to a halt. Then, the astrophysicists Saul Perlmutter, Adam Riess and Brian Schmidt observed stellar explosions that were visible from a great distance and always emitted the same amount of light. They measured their distances and could hardly believe their findings. “The Type 1a supernovae observed exhibited lower brightness levels than expected. It was clear that the Universe was not slowing down as it expanded – quite the opposite, in fact. It is gathering speed and its components are being driven further and further apart at an ever-increasing rate,” explains Thomas Mernik, eROSITA Project Manager at the DLR Space Administration. With this discovery, the three researchers turned science upside and were awarded the Nobel Prize in Physics in 2011. Yet Perlmutter, Riess and Schmidt have left us with one crucial question: “What is the ‘cosmic fuel’ that powers the expansion of the Universe? Since no one has yet been able to answer this question, and the ingredients of this catalyst are unknown, it is simply referred to as Dark Energy. eROSITA will now attempt to track down the cause of this acceleration,” explains Mernik.

An­i­ma­tion - The eROSI­TA X-ray tele­scope - On the hunt for Dark En­er­gy
Very lit­tle is known about the Uni­verse. The in­gre­di­ents that make up four per­cent of its en­er­gy den­si­ty – ‘nor­mal’ ma­te­ri­al such as pro­tons and neu­trons – is on­ly a very small part of the ‘Uni­verse recipe’. What the oth­er 96 per­cent is com­posed of re­mains a mys­tery. To­day it is be­lieved that 26 per­cent is Dark Mat­ter. How­ev­er, the largest share, es­ti­mat­ed at 70 per­cent, is com­prised of Dark En­er­gy. To track this down, sci­en­tists must ob­serve some­thing unimag­in­ably large and ex­treme­ly hot. Galaxy clus­ters are com­posed of up to sev­er­al thou­sand galax­ies that move at dif­fer­ent ve­loc­i­ties with­in a com­mon grav­i­ta­tion­al field. In­side, these strange struc­tures are per­me­at­ed by a thin, ex­treme­ly hot gas that can be ob­served through its X-ray emis­sions. This is where eROSI­TA’s X-ray ‘eyes’ come in­to play. They al­low to ob­serve galaxy clus­ters and see how they move in the Uni­verse, and above all, how fast they are trav­el­ling. We hope that this mo­tion will tell us more about Dark En­er­gy.
Credit: DLR (CC-BY 3.0)

The eROSITA X-ray telescope - On the hunt for Dark Energy from DLR - German Aerospace Center on Vimeo.

Galaxy clusters – a key to Dark Energy

Very little is known about the Universe. The ingredients that make up four percent of its energy density – ‘normal’ material such as protons and neutrons – is only a very small part of the ‘Universe recipe’. What the other 96 percent is composed of remains a mystery. Today it is believed that 26 percent is Dark Matter. However, the largest share, estimated at 70 percent, is comprised of Dark Energy. To track this down, scientists must observe something unimaginably large and extremely hot: “Galaxy clusters are composed of up to several thousand galaxies that move at different velocities within a common gravitational field. Inside, these strange structures are permeated by a thin, extremely hot gas that can be observed through its X-ray emissions. This is where eROSITA’s X-ray ‘eyes’ come into play. They allow us to observe galaxy clusters and see how they move in the Universe, and above all, how fast they are travelling. We hope that this motion will tell us more about Dark Energy,” explains Thomas Mernik.

Map of the entire hot Universe – the largest cosmic catalogue

Scientists are not just interested in the movement patterns of galaxy clusters. They also want to count and map these structures. Up to 10,000 such clusters should be ‘captured’ by eROSITA’s X-ray ‘eyes’ – more than have ever been observed before. In addition, other hot phenomena such as active galactic nuclei, supernova remnants, X-ray binaries and neutron stars will be observed and identified. eROSITA will scan the entire every six months for this purpose and create a deep and detailed X-ray map of the Universe over four years. This will make it possible for eROSITA to produce the largest-ever cosmic catalogue of hot objects and thus improve our scientific understanding of the structure and development of the Universe.

eROSITA – seven X-ray ‘eyes’ looking into the Universe

The German telescope consists of two core components – its optics and the associated detectors. The former consists of seven mirror modules aligned in parallel. Each module has a diameter of 36 centimetres and consists of 54 nested mirror shells, whose surface is composed of a paraboloid and a hyperboloid (Wolter-I optics). “The mirror modules collect high-energy photons and focus them onto the CCD X-ray cameras, which were specially developed for eROSITA at our semiconductor laboratory in Garching. These form the second core component of eROSITA and are located at the focus of each of the mirror systems. The highly sensitive cameras are the best of their kind and, together with the mirror modules, form an X-ray telescope featuring an unrivalled combination of light-collecting area and field-of-view,” explains Peter Predehl, eROSITA Principal Investigator at MPE.

Spektrum-Röntgen-Gamma – a space mission with numerous partners

Spektrum-Röntgen-Gamma (SRG) is a space mission with numerous partners. On the Russian side, it involves the space agency Roscosmos, the space company Lavochkin and the Space Research Institute of the Russian Academy of Sciences (IKI) . The German eROSITA X-ray telescope was developed and built by the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, in collaboration with the Leibniz Institute of Astrophysics in Potsdam (AIP) and the universities of Erlangen-Nuremberg, Hamburg and Tübingen with the support of the DLR Space Administration. Furthermore, the Universities of Munich and Bonn will participate in analysing eROSITA data. The partner institutes involved in the eROSITA telescope have created software for data analysis, mission planning and simulations, as well as components of the hardware. However the main responsibility lay with MPE. “As a rule, an instrument as complex as eROSITA can only be implemented by a major institute with the help of an industrial Prime Contractor. However, together with MPE, we took a different path and let the institute conduct the development work on its own,” says Thomas Mernik. The project management, product assurance and system design were key tasks performed by MPE itself. It also delegated other tasks to industry, such as the manufacturing of the mirrors, the structure, the thermal insulation, mechanical precision parts, electronics boards and much more. “Since eROSITA is about to embark on its journey into space, in retrospect we can say that this approach was very successful and sensible,” says Mernik.

Contact
  • Elisabeth Mittelbach
    Ger­man Aerospace Cen­ter (DLR)
    Com­mu­ni­ca­tions, Space Ad­min­is­tra­tion
    Telephone: +49 228 447-385
    Fax: +49 228 447-386
    Königswinterer Str. 522-524
    53227 Bonn
    Contact
  • Thomas Mernik
    Ger­man Aerospace Cen­ter (DLR)
    Space Ad­min­is­tra­tion
    Space Sci­ence
    Telephone: +49 228 447-111
    Fax: +49 173 3555497
    Königswinterer Straße 522-524
    53227 Bonn
    Contact

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