It delivers a hundredfold improvement. At a thousandth of a second of arc, or less than a millionth of a degree, Hipparcos has fixed directions, distances and motions of stars with an accuracy equivalent to observing an astronaut's height at the distance of the Moon. Astronomers will now re-assess all that they believed they knew about stars and their evolution. Tycho Brahe's revolution in astrometry let Kepler and Newton settle the argument about the nature of the Solar System. All are treated as if they were the same size, so that a star's width on the map gives an impression of its relative distance as measured by Hipparcos.
Numbers identify the most conspicuous stars, in descending order of brightness.
The Sun and many other stars orbit around the centre of the Milky Way Galaxy in a flattened disk. By looking away from the centre, and choosing distant stars from Hipparcos data, astronomers at the Turin Observatory and Oxford University confirm that the disk is not really flat. Outside the Sun's orbit, stars follow tilted orbits. Previous observations of outlying stars gave no more than an impression of their slanting paths. Their inclinations might all have been similar.