HEASARC: The Hidden Universe Revealed

The Hidden Universe Revealed

In its lonely halo orbit 1.5 million miles from earth, the Spektr-RG observatory (SRG for short) scans great circles on the sky around the Sun-Earth L2 point (the first Russian observatory to operate there). SRG carries two telescopes, eROSITA and ART-XC, and these two telescopes map out the entire X-ray Universe every six months. SRG has just finished its first all-sky X-ray survey, which lasted from December 8, 2019 until June 10, 2020. The ART-XC telescope provides the highest-resolution wide-field images in the high-energy X-ray band (4-30 keV), and so provides a revolutionary new view of the X-ray Universe. Because the high-energy X-rays that ART-XC observes can penetrate through vast amounts of dust, ART-XC can find obscured objects hidden to telescopes which operate in lower energy bands. The image above shows the very first all-sky map obtained by ART-XC, in the 4-12 keV band. ART-XC has already detected nearly 600 objects, about two thirds of which are within the Milky Way, and the remainder beyond our Galaxy. The bright areas in the upper left and lower right of the image are the ecliptic poles, which are more highly exposed due to SRG’s orbit around the Sun-Earth line. The all-sky survey will be repeated 7 more times over the next 3.5 years, building up exposure to detect ever-fainter sources and allowing scientists to monitor changes in the X-ray sky. ART-XC is expected to eventually find around 10 thousand hard X-ray sources, providing a unique census of actively feeding supermassive black holes and other strange objects. The ART-XC telescope was developed by the Space Research Institute(Moscow) and the Russian Federal Nuclear Center (Sarov), while its mirrors were fabricated by NASA’s Marshall Space Flight Center.

Published: June 22, 2020 https://heasarc.gsfc.nasa.gov/docs/objects/heapow/archive/large_scale_structure/art-xc_survey.html


SRG Observatory: Half a Year in Space!

Half a year ago, on July 13, 2019, the SRG astrophysical observatory was launched from the Baikonur Cosmodrome. These six months have been full of events: orbit corrections, switch-on and the “first light” of the ART-XC and eROSITA telescopes, their tuning and calibration, the first scientific observations, entry into the operating orbit around the L2 point, and, finally, the long-awaited beginning of the all-sky X-ray survey.

In the course of the calibration and performance verification phase, during daily communication sessions a total of 360 gigabytes of scientific data were received by three ground stations. The first results of these observations were presented at the all-Russian conference “High-energy astrophysics today and tomorrow – 2019”, which was held in December at the Space Research Institute of the Russian Academy of Sciences in Moscow.

On December 8, 2019, the SRG observatory began its all-sky survey. Completing six revolutions per day around the spacecraft’s axis pointed at the Sun, the telescopes of the observatory will complete the first scan of the whole sky already by June 2020, and a total of 8 such surveys are planned to be carried out over 4 years. The illustration shows (in Galactic coordinates) the one sixth of the sky for which data have been obtained during the first month of the survey. During this period, the ART-XC telescope has detected more than 3 million hard X-ray photons (with energies between 4 and 30 keV) from the distant Universe. It is these photons which are shown on the map.

To demonstrate the huge scientific potential of these data, two small fragments of the map are shown on a much larger scale. In the first of them, one can see an extended object – the hot remnant of the Cassiopeia A supernova, which exploded about 300 years ago in our Galaxy (the colors show the image obtained with ART-XC in hard X-rays, while the contours show for comparison an image obtained previously in soft X-rays with the German ROSAT observatory). In the second field, three point-like sources are clearly visible: two X-ray binary systems,

V395 Car and MAXI J0911-655, in our Galaxy, in which matter from a normal star is flowing onto a neutron star (in the latter case, a strongly magnetized neutron star is spinning 340 times per second), and a Seyfert galaxy, IRAS 09149-6206, at a distance of 840 light-years from us, where accretion of interstellar medium onto a supermassive black hole takes place.

The service systems of the SRG spacecraft and all 14 units of the ART-XC and eROSITA telescopes continue to operate in nominal regime, providing the scientists with new data on a daily basis. The unique all-sky X-ray survey is going on!


Spectrum-RG Orbital X-ray Observatory Begins its All-sky Survey

The Spectrum-RG orbital X-ray observatory, launched from the Baikonur kosmodrom on July 13, 2019, begins the survey of the entire sky. On December 8, a spacecraft moving along the orbit around the L2 libration point at a distance of one and a half million kilometers from the Earth, started rotation around the axis directed towards the Earth. Thus, the SRG observatory began scanning the sky along the big circle on the celestial sphere, marking the start of the 4-years long all-sky survey. Following the Earth movement around the Sun, the ART-XC and eRosita telescopes will obtain every six months the map of the whole sky more sensitive than any all-sky data obtained by X-ray astronomers so far. The sum of eight independent sky maps that are expected after four years of the survey will make it possible to achieve record-high sensitivity and find about three million active nuclear galaxies and quasars, hundreds of thousands of clusters and group galaxies, and about half a million active stars, white dwarfs, pulsars and remnants of supernova explosions, neutron stars and black holes in our Galaxy. Comparison of individual sky maps will allow astrophysicists to monitor variability of millions of X-ray sources over the entire sky.

The main scientific goal of sky survey is the study of the large-scale structure of the Universe and the study of the nature of Dark Matter and Dark Energy. At the same time, the unprecedented sensitivity of the survey and numerous selection of X-ray sources of different types that will be discovered during the survey have enormous potential for new discoveries and will gain research in all branches of modern high-energy astrophysics.

The beginning of the sky survey was preceded by the painstaking work of scientists and engineers at the Space Research Institute (IKI) of the Russian Academy of Sciences in Moscow and at the Institute of Extraterrestrial Physics (MPE) of the Max Planck Society in Germany to set up and calibrate two unique X-ray telescopes. This work ended with extensive verification observations, during which the telescopes were tested during real observations of astrophysical objects. The figures below demonstrate the capabilities of the SRG / eRosita telescope for conducting deep sky fields with the size of tens of square degrees (see also the image of the eFEDS mini-survey on the MPE website).

Figure 1 shows an X-ray map of the Galactic disk region (the so-called “Ridge of the Galaxy”) obtained by the eRosita telescope in October 2019. As seen from the image map with a size of 25 squared degrees, numerous X-ray sources were detected, both located in our Galaxy, and quasars located at large distances from the Earth and observed through the Galaxy. Of great interest are Galactic objects: clusters of young stars emitting in X-rays, stars even less massive than our Sun, but having corona emitting in X-rays thousands of times brighter than the corona of our Sun. The map also shows X-ray pulsars: rapidly rotating magnetized neutron stars, the remnants of supernova explosions in which shock waves emit X-ray photons due to collisions of gas detached from a dead star with the surrounding interstellar matter. The map exhibits zones of diffuse X-ray emission. Blue and green colors correspond to high photon energies emitted by a gas with a temperature of tens of millions of degrees, and red color corresponds to a colder gas with a temperature of hundreds of thousands to a million degrees.

The Lockman Hole is a unique area in the sky where the absorption of X-rays by the interstellar medium of our Galaxy reaches its minimum value, which allows us to study distant quasars and clusters of galaxies with record sensitivity. In the sky region with the size of 20 square degrees, the eRosita telescope detected about 6,000 X-ray sources (Figure 2). The vast majority of these sources are the active galactic nuclei and quasars, the radiation of which is associated with the accretion of matter into a supermassive black hole. According to photometric redshift estimate, the most distant of them are located at redshifts up to z ~ 4-5. Also found more than 100 clusters of galaxies and several hundred active stars located in our galaxy.

The images shown above were obtained within the Russian quota of observational time of the eRosita telescope, and were analyzed by the scientists of the high-energy astrophysics department at IKI.

“Spectrum-RG: 100 days in flight” press conference

Link to broadcast: http://pressmia.ru/pressclub/20191022/952527193.html

October 22 at 14:30 MSK at the International Multimedia Press Center of the MIA “Russia Today” will host a multimedia press conference on the topic: “Spectrum-RG: 100 days in flight”.

The participants:
– Scientific leader of the Spectrum-RG project, academician of the RAS Rashid SYUNYAEV;
– Deputy Head of Department – Head of Department of Roscosmos State Corporation Viktor VORON;
– Deputy Head of  NPOL Ilya LOMAKIN;
– Deputy Scientific Director of the Spectrum-RG project, Corresponding Member of the RAS Eugene CHURAZOV;
– Leading Researcher at IKI, Corresponding Member of RAS Marat GILFANOV;
– Principal Investigator of the ART-XC telescope, head of the high-energy astrophysics department at IKI Mikhail PAVLINSKY;
– Head of the Department of Ground-Based Scientific Complexes, IKI RAS Vladimir NAZAROV.

Link: https://ria.ru/20191021/1560017579.html

HEASARC Picture of the week

Seven First Lights of ART-XC

One of the most exciting times in the life of any astronomical observatory is achieving “first light“, the first time a telescope produces an image of an astronomical object. For space-based observatories, this can be a time that’s especially nerve-wracking, given the remote nature of the science and the fact that it can be difficult to address problems in deep space. As capabilities grow, and observatories are placed farther from earth, problems encountered are ever harder to resolve. The Spektr-RG observatory (or SRG as it’s more commonly known) is a Russian-German X-ray observatory, launched on July 13, and currently on a journey to its final staging point, a region of precarious orbital stability in the earth-Sun system called “L2”, about a million miles from earth along the earth-Sun line. Once it arrives at L2, SRG will survey the entire sky every six months over the next four years. SRG consists of two observing instruments. The Astronomical Roentgen Telescope X-ray Concentrator (ART-XC) instrument consists of 7 individual telescopes whichwill generate images of the X-ray sky in the energy band from 5 kilo-electronvolts up to 30 kilo-electronvolts, which is about 3 times higher in energy than most other imaging X-ray observatories, like ChandraXMM-Newton and Swift. ART-XC was developed by the Russian Academy of Sciences’ Space Research Institute, in cooperation with the Russian Federal Nuclear Centre; NASA’s Marshall Space Flight Center provided ART-XC’s X-Ray mirrors. The image above is the first light image from the 7 ART-XC telescopes, obtained on July 30, 2019. This image shows the well-known X-ray pulsar Cen X-3, a binary system in which a spinning neutron star (rotating once every 4.8 seconds) is in a 2-day orbit around Krzeminski’s star, a massive star about 20 times the mass of the Sun. ART-XC can also measure the time variation of the observed X-rays, and the plot on the bottom of the image clearly shows the 4.8 second X-ray variation of the pulsar as measured by ART-XC. eROSITA, developed by Germany’s Max Planck Institute, is the second instrument on SRG, and is expected to achieve first light in the coming weeks.

Published: August 12, 2019 


INTEGRAL coordinated observations of Cen X-3

31 July 2019 INTEGRAL is currently observing the High Mass X-ray Binary Cen X-3. The source is the target selected for the first light of the ART-XC detector onboard the Spektr-RG mission.

INTEGRAL observations will provide complementary information of the source at hard X-rays and will help to characterise the performance of the ART-XC detector in space. Spektr-RG was launched from the Baikonur Cosmodrome on 13 July 2019. We wish sucessful operations to our Spektr-RG colleagues.

Source: INTEGRAL ESA Mission

ART-XC First light

On July 30, 2019 the first images of Cen X-3 X-ray pulsar have been obtained with ART-XC telescope onboard Spektr-RG mission.

Quick-look data analysis demonstrated a strong pulsations with known period of 4.8 seconds.


Images of the X-ray pulsar Cen X-3 obtained with seven ART-XC telescope modules. The location of the images corresponds to the location of the telescope modules. Bottom panel: the pulse profile of Cen X-3 folded with the period of about 4.8 s, registered by the ART-XC telescope from this source.

More detailed investigations will be later presented in official press release.

Last, but not the least, there is a little film, showing how brightness of the pulsar changes – through the eyes of ART-XC

HEASARC: The Launch of SRG

The image above shows the launch of Spectrum-Roentgen-Gamma from the Baikonur Cosmodrome in the Republic of Kazakhstan on July 13, 2019. Spectrum-Roentgen-Gamma (also called Spektr-RG, or SRG for short) is a Russian-German space observatory (with contributions from NASA), which will explore the entire high-energy X-ray Universe. The primary instrument on SRG is the “extended ROentgen Survey with an Imaging Telescope Array” telescope, better known as eROSITA. eROSITA will perform an unprecedented, 4-year long survey of the entire X-ray sky, greatly improving upon the only prior imaging all-sky X-ray survey, obtained by the German-US-UK ROSAT observatory in the early 1990s. The eROSITA survey will be obtained over a 5-times wider X-ray energy band, extending from 0.2 keV up to 10 keV, and to a much higher sensitivity than achieved by the ROSAT All-Sky Survey. The Astronomical Roentgen Telescope – X-ray Concentrator (or ART-XC) on SRG will expand the energy range of SRG to even higher energies, up 30 kilo-electron volts. One of the primary goals of SRG is to detect tens of thousands of distant galaxy clusters to determine the large scale structure in the Universe and test our understanding of the mysterious dark energy which drives the Universe apart. SRG will observe the Universe from a parking orbit at the Sun-Earth L2 point, a region of gravitational stability about a million miles behind Earth along the Sun-Earth axis. SRG will execute its 4-year all-sky survey by orbiting around the Sun-Earth axis every 4 hours. After this survey, SRG will spend 3 years taking detailed observations of individual celestial objects including galaxy clusters, active galactic nuclei, stars, neutron stars and black holes.

Published: July 15, 2019

eROSITA – the hunt for Dark Energy begins

(18 June 2019 – DLR) On 21 June 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.

erosita 1

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. (courtesy: Roscosmos/DLR/SRG/Lavochkin)

erosita 2

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. (courtesy: P. Friedrich/MPE)

erosita 3

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. (courtesy: P. Friedrich/MPE)

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.

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.

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