Beside the myth that black hole entering a planetary system will suck everything into its event horizon, there is another misconceptions people often assign to black holes and stars in general. Due to the way heliocentric principle is taught in classes, some students often get the impression that sun, stars and other objects with stellar mass like black hole are always stationary. This is actually a misconception and this article was written to explain why it is a misconception. In space it is impossible for anything with mass to remain stationary relative to any inertial reference frame.

Why it is impossible for black holes to remain stationary?

First, we have to understand that every object having mass is going to exert gravitational acceleration. The strength of this gravitational acceleration is proportional to the mass of an object and inversely proportional to the distance from said objects. This means that as long as there is any other object in our universe, a stationary object is going to be accelerated toward said object. Any stationary object would never retain its stationary status relative to any inertial reference frame or relative to the reference frame of any other objects with mass for more than 0 seconds.

image properties of author

image properties of author

Both images shown above are snapshots generated by a gravity simulator. As the data panel suggested in the first image, both stars were stationary relative to each other at April 15th 2009. However as time goes on, both stars are attracted toward one another because each of them exert gravitational acceleration. As the data panel show it in the second image, both stars are closing one another at 0.022105 Astronomical Unit per Day in May 25th.

Second, we have to understand that there are billions of stars in our galaxy alone. The mass of our own galaxy is approximately 100 billion times the mass of our sun. Such a colossal mass is going to exert considerable gravitational acceleration even for object thousands light years away from it. Our sun for example orbit the center of our galaxy with orbital velocity of 220 kilometer per second relative to the barycenter of our galaxy.

Any other stars in our galaxy also orbit the barycenter of our galaxy. Because of considerable difference in their initial position and hysteresis, each of those stars have different orbital velocity. The difference in velocity means that each of those stars are not going to be stationary relative to one another. The velocity difference however is so small compared to the distance between stars, so we need very long period of time before we can tell the difference. Anyway, the starry sky that we see today is considerably different from the starry sky the dinosaurs saw 220,000,000 years ago.

Third, stellar black holes typically only have mass around several solar mass (that is why they are called stellar black holes), this is very small compared to the mass of the galaxy itself. The black holes just like other stars are going to orbit the galactic core with different orbital velocity relative to other stars. This means that it is possible for the black hole to move around relative to other stars.

Conclusion

We have to understand that in space nothing could really be at rest relative from any inertial reference frame and from the reference frame of any other objects with mass. Object with mass always exert gravitational acceleration and acceleration always make stationary objects to gain velocity. As black holes and stars are simply objects with mass, it is impossible for them to remain stationary.

My other articles:

• Do Heliocentrism Means That the Sun is Stationary?
• Gravity Simulators and Their Role in Astronomy
• Will a Black Hole Entering Our Solar System Suck Everything In?
• Funny Childhood Misconceptions
• Why Most of Us Associate Nudity with Pornography?