A place in the shade
Unlike many space telescopes orbiting the Earth , Gaia will observe from a point much farther, 1.5 million kilometers from us. This point, called the Lagrangian point L2, is a region of gravitational equilibrium in the Earth-Sun system, ie where the gravitational pull of the Sun and the Earth balance each other almost exactly. It is a vantage point, because in the L2 Sun’s light is blocked by the Earth. In this region of continuous shadow, the satellite can then observe continuously without being disturbed by sunlight. Other space observatories, such as the Planck telescope, in orbit around L2 for the same reasons.
The journey to L2 will last about three weeks, and then it is expected that Gaia reaches its destination after the first week of January. At this point will have already deployed its solar screen ten feet in diameter and will be powered by six solar panels installed on the same screen. Once in L2 satellite, weighing about 2 tons, will be subjected to the initial stages of calibration, which will last about three months. After these stages of calibration and commissioning, will be ready to begin his long census of the Milky Way.
With the eyes of Gaia“For the first time we can measure directions and distances on a galactic scale,” said Mario Lattanzi INAF-Astrophysical Observatory of Turin, in charge of the coordination group Italian “It’s like when cartographers drew the first maps to guide the captains of ships. In five years we will have the largest celestial map ever made. “
In fact, those five years, the satellite will measure position, distance and speed over a billion stars, leading also measures spectroscopic to determine other physical parameters such as temperature or surface gravity. The three-dimensional map that will result will enable astrophysicists to study the composition of our Galaxy and to understand the formation and evolution.
Gaia will observe about a billion and a half stars to magnitude 20, or about 1 million of times weaker of the stars visible to the naked eye. For each, you can measure the position in the sky with a precision of 10 millionths of a second of arc, which is equivalent to the ability to measure the Earth from the fingernail of an astronaut on the moon! The satellite has two ” eyes “very special: two telescopes looking in two directions of the sky separated by 106.5 °. By turning on its axis about every six hours, Gaia will map the sky with these two telescopes. The light is sent, with an appropriate system of mirrors, on a focal plane where it is a complex “retina” electronics, consisting of 106 CCD detectors, which in total form a huge room 1 Gigapixel. Looking at the sky repeatedly over the years, Gaia will highlight the motion of stars in space. Moreover, exploiting the phenomenon of parallax, with a well known technique in astronomy the satellite can also determine the distance of the individual stars. But in his long and complex stellar census, Gaia could also reveal some new secret laws that govern gravity.Einstein under examination
To reduce the astrometric data, the team of Gaia must take account of the laws of the theory of General Relativity, published by Albert Einstein in 1916. According to General Relativity, the presence of a mass deforms the structure of space-time, bending the path of light rays. The Solar System thus becomes a perfect natural laboratory to test Einstein’s equations. The light of the stars observed by Gaia, should in fact make a real “slalom” relativistic caused by the gravitational field of the planets. The researchers Gaia expect to get about a hundred million steps to what could become the largest experiment ever conducted relativity. In this way, Gaia could confirm General Relativity or even reveal small deviations from Einstein’s theory. This would have profound implications on modern cosmological theories that base their predictions right on Einstein’s theory. A planet-hunting Looking
in the areas closer to the Sun Gaia will also thoroughly study the stars smaller and weaker. Within a distance of about 650 light years, scientists expect Gaia fact to determine the spatial distribution and properties of red dwarfs and brown dwarfs. At smaller distances, that is about 80 light-years, The satellite will also detect the presence of extrasolar planets, including rocky planets of Neptune type. To do this, Gaia will observe the faint movements of the stars caused by the gravitational perturbation induced by the planets that revolve around it. Compared to other projects related to the study of extrasolar planets, such as the Space Telescope “Kepler”, the census of Gaia will not discriminate against the stars nor the chemical composition, location, or age. This is very important because at the moment it is not possible to predict, in the light of current theories, which can be of the Suns stars with planetary systems. Only a complete census of Gaia as that can help solve this problem.
A major technological challenge
The menu scientific Gaia is undoubtedly of great importance and, as often happens with such ambitious projects, the related technological challenges are no less. In addition to the realization of the satellite itself, the analysis of the data has in fact necessitated the development of methods and computing infrastructure appropriate. For example, to obtain the location and other information for each star, it is necessary to apply a series of complex adjustments that take into account the perturbation of the optics, and other effects related to the propagation of light in space. Given the billion and a half stars of Gaia, one becomes aware of the problem easily. All measurements must then be converted into positions on the celestial sphere. A major project, for which in 2006 was founded a consortium of data analysis and processing (DPAC), which counts more than 400 scientists in 22 countries. Inside the DPAC, the center of Italian processing (DPCT), based in Turin, will verify and calibrate the astrometric information. “The Data Centre built in Turin at ALTEC, which will also use the FERMI supercomputer installed at CINECA in Bologna, has been sized to handle and store the enormous amount of data that will be collected by the Gaia satellite during its operational life, “says Barbara Negri, head of ASI Exploration and Observation of the Universe. The implementation of the DPCT in fact saw the participation of an industrial partner as ALTEC-Turin: “The Data Processing Center Italian in Turin has been a great technological challenge from the point of view of production that put to the test success with our technical capabilities, “said Luigi Maria Quaglino, CEO of Altec,” and now we are ready for the operational phase to provide the necessary support to industrial science team for a full exploitation of the data. “
A mountain of DVD
At the end of the five year mission, Gaia will have racked up one of the largest astronomical catalogs ever created, which will be available to scientists around the world. It is estimated that the catalog will occupy about one petabyte, or 1 million Gigabite, more or less equivalent to 200 thousand DVD.
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