Wednesday, December 18, 2013

New Esa-probe: "Gaia" to 3-D map of the Milky Way drawing - Spiegel Online

Whether subtle flash of thought or quip – who occasionally uses the short message service Twitter, knows this problem: when 140 characters is final. So you have to learn to focus on the essentials. The new flagship of the European Space Research is now in a sense a similar challenge. The launching into space on Thursday telescope “Gaia” is to build the largest and most detailed to date 3D map of the Milky Way. And because the two-ton probe has a digital camera with an unprecedented resolution on board, they must consider carefully what data they even radioed to Earth.

two telescopes to detect the probe position, color and brightness of a total of a billion stars. With approximately every tenth of them also the radiation spectrum is determined. It can be seen among other things, the chemical composition. But has “Gaia” an image sensor on board, which consists of 106 individual detectors. Together, they bring it to almost a billion pixels. This is about 50 times as much, can boast such a professional SLR camera.

“‘Gaia’ is the greatest discovery machine astronomy,” says Alvaro Giménez Cañete, Esa-Director of Science and Robotic Exploration. This will Europe “a pioneer in precision astronomy”. Cheap it is not, the mission cost is 740 million euros. Plus another 200 million euros for the data processing.

200,000 DVDs would be necessary to store

Even the new high-tech device can watch one percent of all stars in our galaxy just once. The Milky Way is a disk, about 100,000 light-years in diameter and 3000-16000 light years thick. And even elementary questions – such as on the number of spiral arms of our galaxy – are difficult to answer. But it seems clear: The Milky Way has about a hundred billion suns


to examine a fraction of them himself, is a gigantic job: per day to make “Gaia” about forty million individual measurements – and send as 50 gigabytes of data back to Earth. There, the 35-meter antennas of Esa listen in New Norcia (Australia), Cebreros (Spain) and Malargüe (Argentina) to the signals. Is controlled by the mission by the European Space Operations Centre in Darmstadt.

five years, will that work as if everything goes according to plan. During this time, each observed star is to be taken about 70 times targeted. Here, according to Esa calculations 900 billion observational data come together with a total volume of one petabyte. Six data centers take care of the flood of data, for storing them 200,000 DVDs would be necessary.

“Galactic microscope”

A group of more than 430 scientists (“Gaia Data Processing and Analysis Consortium”) to ten years to evaluate the information. First partial results will probably only be available in three to four years, and the final evaluation even at the earliest from 2022.


now all the effort? “Gaia” is not only the sky more accurately measured than previous missions such as “Hipparcos”, in which the Europeans had early nineties mapped 2.5 million stars. The new probe will also rediscover cosmic objects, including:

  • up to 250,000 unknown asteroids and comets in our solar system
  • hundreds of thousands of quasars, ie nuclei of distant active galaxies,
  • thousands of exoplanets with planetary systems
  • thousands of supernovae, and
  • tens of thousands of brown dwarfs, ie stars whose mass was too low to start the cosmic fires of nuclear fusion in its interior.
  • Built the probe was at Astrium in France. Eric Beranger, chief of the relevant subsidiary, called “Gaia” a “galactic microscope” and the “Eye of the Universe”. On the one hand the finest PR talk, on the other hand, an indication of how complicated was the development.

    Almost 20 years to prepare for the mission lasted. Last, the start was again delayed because literally had to be replaced at the last second parts of the communication technology.

    Now, however, it should finally begin. Following the launch of a Soyuz-ST rocket from the launch site in French Guiana needs “Gaia” for about a month until her workplace. The reason is that it will make its observations on the so-called Lagrange point L2, a million miles away from Earth. There, the gravitational forces of the Sun and the Earth cancel. The probe can thus pull in unison with our planet around the central star.

    Otherwise, it applies its influence as far as possible be avoided. The sun shines so bright that it would blind the sensitive camera chip. Also, Moon, Earth, and many stars are too bright for “Gaia” So the probe radiation sources to some extent in the back. A ten-meter structure at the bottom, which can be thought of as a kind of apron, makes this possible. It is expanded only at the observation point, and is also used to power the probe.

    What Twitter is concerned: “Gaia” has long since been a separate account. And can there ever learn as much information to accommodate little space.

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