Comment by photochemsyn | Hacker News Reader

Comment by photochemsyn | Hacker News Reader

As NASA notes:

> "...the Sun - in fact, our whole solar system - orbits around the center of the Milky Way Galaxy. We are moving at an average velocity of 828,000 km/hr. But even at that high rate, it still takes us about 230 million years to make one complete orbit around the Milky Way!"

It takes a vast amount of energy for a stable orbiting body to reach the center of mass of the object it is orbiting around, for example that's why the small Parker Solar Probe (launched 2018) required the massive Delta 4 heavy rocket to provide the boost energy:

https://www.youtube.com/watch?v=AlyuSwRSVHU

So, 'dragged' isn't really the right way to think about it, is it? If two stars collided there must have been some massive energy input into the X7 object which accelerated it towards the black hole (it might instead have been accelerated away from the black hole, depending on the dynamics of the collision). Hence, 'it was shoved towards the black hole' is perhaps a more accurate view than 'it is being dragged by the black hole'.

It would have been shoved backwards relative to the original orbit, perpendicular to the direction of the black hole.

When you think of orbiting as "falling and missing continuously", the lowest-energy way to stop missing is to stop moving forward.

It's not tugged towards the black hole in a straight line - the word "dragged" fits best if you interpret it like the drag on an airplane, something that's impeding the movement of the body and sucking energy away.

I suppose a lot depends on the frame of reference, but if this came about from two stars colliding, it seems safe to assume these two stars were in relatively stable orbits around the galactic center. Those orbits were stable because of the dragging effect of the black hole, much like Earth's orbit is stable because of the dragging effect of the Sun.

If the Earth smacked dead-on into another Earth orbiting in the opposite direction around the sun, I imagine most of the combined mass would start falling into the sun due to net loss of momentum, although jets of material might get accelerated further out into the solar system, as well as inwards. In that case 'dragged' might make more sense.

The case for two stars seems more complicated, they start orbiting each other before merging, which could be a very energetic event if they were large enough, i.e. a 'merger-triggered core collapse supernova'.

I just love the Delta's giant fireball at launch

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