Astronomers have created a new 3D map of the interstellar gas in the local area around our Sun. “Local” is a relative term, as the map extends to an area of 300 parsecs and provides new absorption measurements towards more than 1800 stars. The group of astronomers, from the US and France, were able to characterize the properties of the interstellar gas within each sight line. The new map will allow astronomers to better understand the interplay between the evolution of stars and their exchange of matter with the ambient interstellar medium.
The local area around our Sun has been studied with many surveys at various wavelengths, but the whole picture is still far from being either complete or fully understood. Our sun resides in a “cavity” a region of very low-density neutral gas, known as the Local Cavity. Theories of the general interstellar medium require that these large rarefied cavities exist, and astronomers believe the cavities were formed by the combined action of energetic supernova events and the outflowing winds of clusters of hot and young stars. The history of our Local Cavity is still speculative, but astronomers think it was created about 15 million years ago by a series of supernova outbursts, with the last re-heating happening about 3 million years ago.
The team gathered their data primarily from the European Southern Observatory in Chile, and combined it with previously published results. The map (shown above) shows the sodium map of the interstellar gas density within 300 parsecs. The white area surrounding the Sun (at the center of the map) corresponds to the Local Cavity. It is about 80 parsecs in radius in most directions and is surrounded by a highly fragmented “wall” of dense neutral gas. The various gaps in the wall are “interstellar tunnels” and represent rarefied pathways into other surrounding interstellar cavities. Maps of the distribution of calcium have never been made before, and they reveal that the Local Cavity contains numerous filamentary structures of partially ionized gas that appear to form in a honeycomb-like pattern of small interstellar cells.
Source: Astronomy and Astrophysics