VOA常速英语:ESA to Make 3D Map of Milky Way

The European Space Agency this week successfully launched the star-mapping satellite Gaia on a mission that will take it more than a million kilometers from Earth - to create the first three-dimensional (3D) map of our galaxy, the Milky Way.

The two-ton satellite, launched from the European Space Agency抯 center in French Guiana aboard a Russian Soyuz rocket, reached the initial orbit and deployed a 10-meter circular sunshield to keep the instruments on-board, including a telescope, cool. In order to focus on very distant and faint stars, Gaia has to be mechanically and thermally stable, so it has almost no moving parts.

Mark McCaughrean, the mission's chief scientist, says, 捏t will measure the positions of a billion stars but also their speeds, their motions. And with that we can run a movie of the Milky Way. We can run it forwards, into the future, how the Milky Way will develop by looking at all the stars and how they move. But we can run it backwards as well, and we can see how the Milky Way actually formed in the first place.?BR>
Gerard F. Gilmore, a professor at Cambridge University's Institute of Astronomy, says the three-dimensional picture will eventually cover half of the Milky Way and provide new knowledge about what keeps it together.

揂nd the particular interest that I have in here, locally, is in the nature of dark matter," he said. "What is dark matter made of? Dark matter is most of the weight in the Milky Way. It is dark matter that holds the Milky Way together. If there weren磘 all this dark material, our sun would fly off...away from the galaxy. The whole galaxy would fall apart.?BR>
The Gaia satellite will be moved to a distance of 1.5 million kilometers from Earth, to a gravitationally stable point called L2, where it will start its five-year mission of taking approximately 70 images of each star in our galaxy, building a catalog of about one billion stars.

L2 is also designated as the parking space for NASA抯 supersensitive infrared James Webb Space Telescope, scheduled for launch in 2018.

The overal cost of the Gaia mission is around $1.3 billion.