The European Space Agency is preparing to launch a satellite that will produce the most accurate three-dimensional map of our part of the Milky Way.
The agency says its Gaia satellite due to launch Thursday from French Guiana at 6:12 a.m. (0912 GMT; 4:12 a.m. EST) will survey some 1 billion stars in our galactic neighborhood.
Even that is just a small fraction of the stars in the Milky Way.
Gaia will also use its 1,000-megapixel camera to hunt for planets, asteroids and comets beyond our Solar System.
ESA says scientists are hoping the satellite's sensitive instruments can be used to test a key part of Albert Einstein's General Theory of Relativity that predicts "dips" and "warps" in space caused by the gravity of stars and planets.