Russian X-ray telescope that will open up new space objects

[ScienceNology] - International Orbiting Astrophysical Observatory «Spectrum-Roentgen-Gamma» (AWG) will be equipped Russian X-ray telescope that will open up new space objects.

The project agreement was signed by the AWG at the international air space between the Federal Space Agency (Roskosmos) and the German Aerospace Center (DLR). AHWG Observatory is scheduled to start in 2012 for a term of seven years. It is designed to survey the entire sky specular X-ray telescopes in the hard energy range (0,5-11 keV). Review will be a record due to its high sensitivity, which is a large effective area of mirror systems, high angular resolution optics and extremely large telescopes for such a field of view.

As the press service of the Institute for Space Research (IKI), with the new X-ray Observatory to be found about 100 thousands of new galaxy clusters and more than 3 million new active nuclei of galaxies in the center of which, presumably, are superheavy black holes. Information about large-scale structure of the universe, obtained on the basis of clusters of galaxies is crucial to study its evolution, including, for the understanding of the role it played in the so-called «dark energy». In addition, based on data on AHWG nuclei of active galaxies can be studied the growth and evolution of superheavy black holes.

Earlier X-ray review of the entire sky was made by the satellite ROSAT (Germany / United States / United Kingdom, 1990-1999), but only in the «soft» (0,5-2 keV) energy range and the worst, about 40 times the sensitivity. Because of the strong interstellar or internal absorption at low energies, many interesting X-ray sources were not detected.

The observatory will be equipped with a two AHWG specular X-ray telescopes: eROSITA (Germany) - the basic tool for the mission weighing 760 kg, which works in the energy range 0,5-10 keV, and the unit ART-XC (Russia), weighing 350 kg, supplementary tool in a German hard energy range 6-30 keV.

Orbit, which will work Observatory (in the vicinity of the point of L2) - one of the five existing in the sun - the Earth points where the perturbing gravitational effects on the spacecraft from the Sun and the Earth reduced to a minimum. Point L2 (Libration point) is located on the sun - the Earth at 1.5 million miles of Earth.

First, the observatory will not pass through the Earth's radiation belts, which have to disconnect the equipment from the damaging effects of the flow of charged particles in the electronic components of devices. Secondly, here the most comfortable temperature, because the sun is always located on the one hand, to the Earth to the Moon and very far away, and the heat flow from them do not make any perturbation, temperature at which the work equipment is stable. Finally, the apparatus of the orbit does not go into the Earth's shadow, and solar panels will be able to ensure energy devices.

Home Organization for scientific equipment Observatory - IKI. According to ground-and space complex «AHWG» parent organization - the Scientific-Production Association to them. SA Lavochkin. The project also involved the Russian Federal Nuclear Center - All-Russian Scientific Research Institute of Experimental Physics (Sarov), in cooperation with the IKI is developing the telescope ART-XC. On the German side of the project involved the German Aerospace Center, Institute for Extraterrestrial Physics, and several other institutions of society to them. Max Planck and universities.

Source :  Science and life , 20 August 2009

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Tiny Flares Responsible for Outsized Heat of Sun's Atmosphere

<-- This false-color temperature map shows solar active region AR10923, observed close to center of the sun's disk. Blue regions indicate plasma near 10 million degrees K. Credit: Reale, et al. (2009)

"Why is the sun's corona so darned hot?" asks James Klimchuk, an astrophysicist at the Goddard Space Flight Center's Solar Physics Laboratory in Greenbelt, Md.

The mystery of why temperatures in the solar corona, the sun's outer atmosphere, soar to several million degrees Kelvin (K) —much hotter than temperatures nearer the sun's surface—has puzzled scientists for decades. New observations made with instruments aboard Japan's Hinode satellite reveal the culprit to be nanoflares.

Nanoflares are small, sudden bursts of heat and energy. "They occur within tiny strands that are bundled together to form a magnetic tube called a coronal loop," says Klimchuk. Coronal loops are the fundamental building blocks of the thin, translucent gas known as the sun's corona.

Scientists previously thought steady heating explained the corona's million degree temperatures. The steady heating model indicates that a coronal loop of a given length and temperature should have a specific density. However, observations showed that coronal loops have much higher density than the steady heating model predicts. Newer models based on nanoflares can explain the observed density. But no direct evidence of the nanoflares existed until now.

Two active regions appear as bright areas on this full-disk image of the sun, taken with the Hinode spacecraft's X-Ray Telescope. Credit: NASA -->

Observations from the NASA-funded X-Ray Telescope (XRT) and Extreme-ultraviolet Imaging Spectrometer (EIS) instruments aboard Hinode reveal that ultra-hot plasma is widespread in solar active regions. The XRT measured plasma at 10 million degrees K, and the EIS measured plasma at 5 million degrees K. "These temperatures can only be produced by impulsive energy bursts,"says Klimchuk, who presented the findings on August 6 at the International Astronomical Union General Assembly meeting in Rio de Janeiro, Brazil.

"Coronal loops are bundles of unresolved strands that are heated by storms of nanoflares."

Coronal heating is a dynamic process. The brightness of the observed X-ray and ultraviolet emission is strongly dependent on the density of the coronal plasma. Where there's low density, there isn't much brightness. Where there's high density, there's a lot of brightness. The corona is mostly bright at about 1 million degrees K.

Klimchuk and colleagues constructed a theoretical model to explain how plasma evolves within these coronal tubes and what causes temperatures to skyrocket. "We simulate a burst of heating and see how the corona responds," says Klimchuk. "Then we make predictions about how much emission we should see from plasma of different temperatures."

Klimchuk surmises that when a nanoflare suddenly releases its energy, the plasma in the low-temperature, low-density strands becomes very hot—around 10 million degrees K—very quickly. The density remains low, however, so the emission, or brightness, remains faint. Heat flows from up in the strand, where it's hot, down to the base of the coronal loop, where it's not as hot. This heats up the dense plasma at the loop’s base. Because it is so dense at the base, the temperature only reaches about 1 million degrees K. This dense plasma expands up into the strand. Thus, a coronal loop is a collection of 5-10 million degree K faint strands and 1 million degree K bright strands.

"What we see is 1 million degree K plasma that has received its energy from the heat flowing down from the superhot plasma," says Klimchuk. "For the first time, we have detected this 10 million degree plasma, which can only be produced by the impulsive energy bursts of nanoflares."

The Hinode observations and the scientists' analysis verify that nanoflares are occurring on the sun and that they explain much and perhaps most coronal heating. The observations also confirm "there is some nanoflare activity everywhere" in the sun's active regions, says Klimchuk.

Nanoflares are responsible for changes in the X-ray and ultraviolet (UV) radiation that happen as an active region evolves. X-ray and UV get absorbed by Earth's upper atmosphere, which heats up and expands. Changes in the upper atmosphere can affect the orbits of satellites and space debris by slowing them down, an effect known as "drag." It is important to know the changing orbits so that maneuvers can be made to avoid space collisions. The X-ray and UV also affect the propagation of radio signals and thereby adversely affect communication and navigation systems.

The discovery that nanoflares play an important and perhaps dominant role in coronal heating paves the way to understanding how the sun affects Earth, our place in the universe.


Source : NASA / Goddard

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