When Did the Center of the Milky Way ‘Explode’?

About 3.5 million years ago, the supermassive black hole at the heart of the Milky Way seemed to experience a period of increased activity. Even from our distance of 27,000 light-years away on Earth, it would have been observable as a faint glow, perhaps even triggering wonder in early human ancestors. Some popular science articles have described this event as an explosion, but it falls far short of the energy and duration of human-made explosions. In terms of energy, it was vastly stronger, but most importantly, it lasted for thousands of years.

What Really Happened at the Galactic Center?

The center of the Milky Way has not experienced a 'supernova-type' explosion. Rather, it contains a massive black hole that releases a significant amount of energy every time something massive falls into it. This process is not an explosion, as black holes do not ‘explode’ in the conventional sense. Instead, a black hole simply continues to draw in matter, consuming it and preventing it from ever returning.

Other galaxies, like Seyfert galaxies such as NGC 1068 and Messier 77, contain supermassive black holes in their cores. These galaxies were once thought to be in a state of perpetual 'explosion' until better telescopes revealed that the phenomena observed were due to the black holes swallowing matter.

The Supermassive Black Hole at the Galactic Center

The heart of our galaxy is characterized by a supermassive black hole with a mass of just over 4 million times our sun's mass. This black hole occasionally attracts and devours large celestial bodies. While this process does release a considerable amount of energy, in the grand scheme of things, the galactic center remains fairly quiet compared to other black holes in the universe. The black hole continues to attract and consume matter, but it does not ‘explode’ in the way that stars in supernovae do.

The Misconception of Black Hole Explosions

"The center is characterised by a supermassive black hole of a little over 4 million times our sun’s mass. It will occasionally have things drift into it which will spark things up a bit. In general it is fairly quiet as SMBs go."

Common misunderstandings about black hole behavior often stem from a lack of understanding of the science behind these phenomena. Black holes do not have a traditional explosion or eruption in the way that we think of them in the realm of everyday experience. Despite the energy release that occurs as matter approaches and falls into the black hole, the black hole itself remains stable and continues to consume mass indefinitely.

While these events are fascinating and certainly visible to astronomers, they do not fit the common vernacular of an 'explosion.' The term is often used colloquially to convey a sudden and intense release of energy, which is not the case in the context of black holes. Understanding these cosmic phenomena requires a deep appreciation of the complex interplay between gravity, mass, and energy that defines the behavior of black holes in the universe.