So, I’m a science fiction writer…and the scenario is a nomad black hole of 10 to 10,000 solar masses that is discovered on its way into the inner solar system at a closing speed of 8000 km/sec relative to the sun…
Does anybody have any idea of a framework to figure out the largest black hole that I could use that wouldn’t kill everyone on Earth? So I suppose (a) that would leave Earth in more-or-less a similar orbit and (b) wouldn’t fracture the crust/mantle to such an extent that the entire surface would be destroyed.
Play around with this simulator ROGUE STAR, which allows you to send a “rogue star” of various masses through the solar system at various speeds. Generally the faster the better, by the way - the slower the star moves, the more time it has to affect the orbits of stars.
No. Black holes are denser not more massive after they collapse; while you’ll experience the famous exotic effects of a black hole if you get really close up, at a distance its gravity is no different than that of any other object of the same mass.
Re: star speed… if the star was going fast enough, it could have any desired mass due to relativistic mass increase at high speeds. How fast does something need to go to double its mass? Is there anything in the umiverse that can accelerate stars to relativistic speeds without destroying them?
You might try out Universe Sandbox, a solar system/space phyics/etc simulator, which would allow you to send a user-created object of desired mass, direction, and velocity through the solar system. At least you’d be able to see if it sends anyone we care about careening into the sun.
I understand that a sequel, which models at least some climate effects (due to changes in axial tilt, CO2 and water levels, enormous horrific impact craters, etc) is in alpha at the moment.
I guess the longer term problem would be that the Earth would inevitably be kicked into a different orbit around the Sun…which would mess up everything (either freeze us or bake us). At the same time, though, I’m sure the event would trigger some intense volcanic activity which would kick immense clouds of dust and particles into the air and cool the Earth.
All of that would be for a sequel right now I just need the characters to survive the initial pass!
Ha, yes, these are the sorts of scenarios I’m toying with… in the short term, if we survived an event like this, there would be a lot of cooling from a massive amount of dust and particles from all the volcanic events it would probably trigger
Also, in this scenario - I’ve read that if two black hole collide, the resultant black hole can be accelerated at great speeds due to the combined angular momentum…that’s why I have it going at 8000 km/sec relative to the sun…anyone have any opinions on that?
I thought approaching the speed of light caused your mass to increase, which is why we cannot get TO the speed of light because of infinite mass, or something?
I cannot get the Rogue Star sim to work - I’ve uploaded all the latest Java plug-ins to my browsers, enabled the security settings, clicked “yes” to allow it to run…and tried it on Chrome and on Explorer but it still comes up with an “error cannot run” message…
Actually, I can’t get it to work now either - it’s been some years since I’ve used it, so perhaps it’s not compatible with any modern browser. Sorry about that.
This isn’t quite the same thing - but it’s a solar system simulator that still works for Firefox My Solar System 2.04
As with every other object, a black hole’s gravity depends on its mass, which can be anything from tiny to immense. The only “size” that applies to a black hole is the Schwarzschild radius (the radius of the event horizon).
The OP specified a black hole of 10 to 10,000 solar masses. In this range, “gravity per size” - commonly known as “density” - is indeed greater than most stars. But it’s interesting to note that truly huge black holes (e.g. this one, at 17 billion solar masses) have a rather low density.
I’ve thought about this a bit more. You can calculate the acceleration of the Earth caused by the black hole - it’s G*M/R^2 - where G is the gravitational constant, M is the mass of the black hole, and R is the distance of the black hole from the Earth. But let’s do it in terms of the acceleration of the Earth caused by the Sun - now it’s M/R^2 where M is the mass of the black hole (in terms of solar mass) and R is the distance from the Earth to the black hole in astronomical units; that makes the acceleration of the Earth caused by the Sun equal to 1 - a nice round number.
But it’s not the total acceleration the black hole causes on the Earth that matters - after all the Sun causes more acceleration for the Moon than the Earth does, but the Moon is still orbiting Earth. What you need is the relative acceleration - the difference between the acceleration that the black hole causes on the Earth and the acceleration that the black hole causes on the Sun. As a rough order of magnitude that is M/Re^2-M/Rs^2 (where M is still the mass of the black hole in terms of the solar mass, Re is the distance from the Earth to the black hole in units of au, and Rs is the distance from the Sun to the black hole in units of au. If the black hole is fairly distant from the Sun and the Earth, then this turns out to be M/R^3. If that term is bigger than (say, for the sake of argument) 0.01, then there’s going to be a noticeable affect on the Earth’s orbit around the Sun, which suggests that a supermassive black hole is going to doom us if it gets anywhere near the inner solar system.