Astronomy Picture of the Day—20180806

Discover the cosmos! Each day a different image orphotograph of our fascinating universe is featured, along with a briefexplanation written by a professional astronomer.

2018 August 6

Trapezium: At the Heart of Orion

Image Credit: Data: Hubble Legacy Archive, Processing: Robert Gendler

Explanation: Near the center of this sharp cosmicportrait, at the heart of the Orion Nebula, are four hot, massive stars knownas the Trapezium. Gathered within a region about 1.5 light-years in radius,they dominate the core of the dense Orion Nebula Star Cluster. Ultraviolet ionizing radiation from the Trapezium stars, mostly from the brightest starTheta-1 Orionis C powers the complex star forming region's entire visible glow.About three million years old, the Orion Nebula Cluster was even more compactin its younger years and a recent dynamical study indicates that runawaystellar collisions at an earlier age may have formed a black hole with morethan 100 times the mass of the Sun. The presence of a black hole within thecluster could explain the observed high velocities of the Trapezium stars. TheOrion Nebula's distance of some 1,500 light-years would make it the closest known black hole to planet Earth.