Now, this peaceful picture is brutally disturbed by an international group of astronomers who bring us the message that a black hole of at least a hundred solar masses is likely to ambush us in our own backyard.
Theta Orionis, a fuzzy star in Orion's sword harbouring a massive black hole?
Ok, in true astronomical distances our 'backyard' is at a safe distance of more than a thousand light years, but the above makes it abundantly clear that for an astronomer this black hole is close.
And that is good news as it brings the stars surrounding this black hole within comfortably reach of any decent amateur telescope. Or even within reach of a powerful binocular. Aim your telescope or binocular at the constellation known as Orion, and locate the central star in Orion's sword. In your telescope this central star will reveal itself as a fuzzy object known as Orion's Nebula. At the heart of this nebula you will see four bright stars arranged in a trapezoidal shape: Theta Orionis, better know as the Trapezium Cluster. Together these stars, each weighing in at a dozen to a few dozen suns, are responsible for illuminating Orion's Nebula. This illumination is bright enough to render Orion's Nebula observable in the night sky from almost any city, no matter how bad the light pollution. It is this brightness and the extent of this nebula (roughly two moon diameters) that has made astronomers referring to this nebula as the "Great Orion Nebula".
The trapezium cluster was discovered by Galileo almost four centuries ago. The stars in this cluster have been studied since, and we know already for some time there is more than just four stars in this cluster. We also known these stars to be in a fast whirling motion. This motion has puzzled astronomers and was never fully resolved. And now a few astronomers claim that to explain this whirling motion you have to assume a black hole of at least a hundred solar masses at the center of the trapezium cluster.
Since I first directed a telescope at the night sky, Orion's Nebula has been my favorite object. Once you have looked through a telescope at this massive gas and dust cloud, it is no longer a surprise this stellar nursery is often referred to as to the Great Nebula in Orion or the Great Orion Nebula. Just the suspicion of a massive black hole lurking at the center of this massive cloud, forcing its newborn stars to enter a lethal dance, makes this astronomical object even more compelling.
Whether the suspicion of a black hole being located in Orion's Trapezium Cluster stands up to scrutiny remains to be seen. If confirmed, astronomers will learn a lot by inspecting their backyard.