What prevents the Milky Way from collapsing into the black hole located at its center?

 What prevents the Milky Way from collapsing into the black hole located at its center?

Credit: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)

The black hole located at the center of our galaxy, known as Sagittarius A, possesses an immense mass and is highly compact. With a mass approximately 4 million times that of our sun, one might wonder why the Milky Way does not collapse into it. However, the answer lies in the vast distance between us and the black hole. Sagittarius A is situated about 27,000 light-years away from Earth, which equates to roughly 250 trillion kilometers or 155 trillion miles. This significant distance creates a substantial amount of space between the black hole and the majority of stars in our galaxy.

 

Gravity, as we know, is the force that attracts objects with mass towards each other. The strength of gravity is directly proportional to the mass of an object. Additionally, the closer two objects are, the stronger their gravitational attraction becomes. Given the immense mass of the black hole, one might assume that its gravity would pull everything in the galaxy towards it. However, this is not the case.

 

While gravity is a dominant force, it is not the sole force at play within the galaxy. Another force, known as centripetal force, also comes into play. Centripetal force is responsible for keeping objects in a circular path around another object. To illustrate, consider swinging a ball on a string around your head. The string provides the centripetal force necessary to prevent the ball from flying away.

 

The same principle applies to the stars and planets within the galaxy. They move at high speeds around the center of the galaxy, where the black hole resides. This rapid motion generates enough centripetal force to counterbalance the gravitational pull of the black hole. Consequently, rather than falling into the black hole, these celestial bodies orbit around it in a stable manner.

 

It is important to note that this equilibrium is not flawless. Occasionally, objects can come dangerously close to the black hole and succumb to its gravitational pull. This can occur during stellar collisions or when gas and dust clouds become excessively dense near the galaxy's center. When such events transpire, we witness extraordinary phenomena, including the emergence of jets of radiation and matter shooting out from the vicinity of the black hole's event horizon.

However, such occurrences are infrequent and have minimal impact on the majority of the galaxy. As inhabitants of one of the spiral arms within the Milky Way, we are shielded from the threat of being consumed by the black hole situated at its core. Instead, we can appreciate its magnificence from a distance, observing the dark silhouette it creates, encircled by a radiant halo of light that is actually the result of gravitational bending.