By measuring the distance from the Sun to thousands of individual pulsating stars scattered throughout our galaxy, a group of researchers has published in Science the three-dimensional map of the Milky Way on a larger scale to date.
According Przemek Mroz, from the University of Warsaw, the map reveals the S-shaped structure of the combined star disk of the Milky Way.
Our galaxy has, on average, 100,000 light years in diameter, but only 1,000 light years wide. Within this flattened disk (although slightly deformed), the Sun and its planets are embedded in a curved arm of gas and dust, so the solar system is about 26,000 light years from the turbulent core of the galaxy.
Much of the current understanding of the spiral shape and structure of our galaxy is based on indirect measurements of celestial landmarks and inferences based on other galaxies, but the current three-dimensional map is different, is measured more accurately, as Mroz points out:
Our map shows that the Milky Way disc is not flat. It is deformed and twisted. This is the first time we can use individual objects to display it in three dimensions.
To reach this level of accuracy, basically more benchmarks were obtained.
The researchers measured the periodic variations in the brightness of classical cepheids (massive stars that pulsed radially, varying both in temperature and diameter to produce brightness changes with a very regular stable period and amplitude) in order to accurately determine the distances to these stars. The distance was thus traced to more than 2,400 cepheids along the Milky Way, most of which were identified through the gravitational lens effect, which doubled the number of known classical galactic cepheids.
To collect such a complete and pure sample of cepheids, one has to regularly observe the entire Milky Way for a long period of time. To give some numbers: the galactic disk had been observed for six years, taking 206 726 images of the sky, containing 1,055,030,021 stars, what led to 153 704 543 662 individual observations.