The heart of the Milky Way is dominated by—even defined by—its supermassive black hole (SMBH). It's named Sagittarius A-star (Sgr A*), and it has about 4 million solar masses. Its gargantuan gravitational pull, powerful radiation, and complex magnetic fields shape its surroundings.

Sgr A* is a quiescent SMBH rather than an active galactic nuclei (AGN). It still has an accretion ring, but it's fed by a trickle of material rather than a gluttonous flow. So it doesn't host the type of bright accretion ring characteristic of an actively feeding SMBH.

Astrophysicists can't take their eyes off Sgr A*, and they observe it across multiple wavelengths and probe it and its environment in every way they can. Its proximity to Earth compared to SMBH in other massive galaxies gives researchers an opportunity to study SMBH in greater detail.…