A NASA observatory has closely observed the galactic big ‘sister’ of the Milky Way, spying 40 X-ray binaries, the objects that are said to be main factor in the heating of interstellar gases and thus key drivers of galaxy evolution.

Nuclear Spectroscopic Telescope Array of NASA, or NuSTAR, is a space telescope that can detect some of the highest-energy X-rays generated by the universe. While spying on the Andromeda Galaxy (M31), NuSTAR astronomers didn’t face disappointment.

Just like the Milky Way, Andromeda is a quite huge spiral galaxy present at a distance of nearly 2.5 million light years away. Though the distance sounds like a long way, Andromeda is our closest spiral galaxy neighbor.

Due to its relative closeness, missions, such as NuSTAR, can conduct a detailed study of X-ray emissions of Andromeda. On January 5, some latest findings were presented at the 227th meeting of American Astronomical Society in Kissimmee, Fla.

Daniel Wik of NASA Goddard Space Flight Center in Greenbelt said, “Andromeda is the only large spiral galaxy where we can see individual X-ray binaries and study them in detail in environment like our own. We can then use this information to deduce what’s going on in more distant galaxies, which are harder to see”.

There are two stellar objects present in X-ray binaries, usually a star and one stellar remnant, such as a neutron star or black hole. When the pair orbits each other, the star’s plasma is dragged away by the compact remnant, and when plasma comes toward neutron star or the black hole, the gas faces rapid and strong heating, a process that can result into generation of high-energy X-rays.

With the help of NuSTAR observations of a neighbor galaxy, now astronomers can be able to better understand and know whether the X-ray binaries consist of mainly black holes or neutron stars. They will be able to compare their radiation with the average X-ray emissions from far away galaxies.