How do I make a black hole?

[Sampoerna]

How to create a black hole in Universe Sandbox 2?

[Dan Dixon]

A black hole is just an object who's size is so small that the escape velocity at it's surface is equal to the speed of light.
http://en.wikipedia.org/wiki/Black_hole


Click this button:


From this post:
http://universesandbox.com/forum/index.php/topic,3999.msg38798.html#msg38798
Thanks Bla!

OR

To make any object in Universe Sandbox a black hole:
1 - Select the object
2 - Click on the lock icon next to the mass textbox to lock the mass.
3 - Click on the Diameter text box in the object's properties
4 - Click on 'Black hole' in the diameter popup.

This will set the radius of the object to be really small and make it a black hole.

Try it on our Sun or on the Earth.

Later this year I hope to improve the visuals of black hole objects.

Thanks for the question.

[Dan Dixon]

Posting to bringing this back to the front page. I'll be including these steps in a future "Fun Things to Do" activity in the near future.

[Darvince]

Doesn't Ctrl + W also make the selected object a black hole?

[Technotica]

I have a related question, if you make a sun into a black hole, why do all the objects in the system fly towards the black hole and then get 'sling shotted' (slung shot?) out of the system? Wouldn't the black hole eat them?

I have the collision setting to merge.

[Joshimitsu91]

You can also change the texture colour to dark black for added effect!

I have a related question, if you make a sun into a black hole, why do all the objects in the system fly towards the black hole and then get 'sling shotted' (slung shot?) out of the system? Wouldn't the black hole eat them?

I have the collision setting to merge.

Providing you don't change the mass the planets shouldn't change their paths at all.

If objects are getting slingshotted out of the system, it may because they are passing in a tight eliptical orbit. If the time-step is too large, the calculations can't simulate a close pass-by well and it causes the object to shoot away from the star. This is to do with how the RK4 method (or euler) simulates the system. It may also be worth enabling RK4 if you can.

The black hole will eat any objects that collide with it, i.e. they pass too close or don't have enough speed. It's still possible for objects to orbit a black hole as they do a star, and even for black holes to orbit stars or even planets. The only difference with a black hole is that at its surface the gravity is so intense that light cannot escape, at long ranges it is equivalent to a star (from Newtonian Physics anyway... i'm not 100% sure about in reality, i'm no expert).

I hope this helped, i'm sure someone will correct me if i'm wrong! 

Josh

[Joshimitsu91]

Posting to bringing this back to the front page. I'll be including these steps in a future "Fun Things to Do" activity in the near future.

It might be a good idea to make a sticky post with some links to other threads, like this thread and the tutorials on binary star systems etc?

Doesn't Ctrl + W also make the selected object a black hole?

Yes it does, thanks for the tip! (Lol the moon has to be 0.22 mm in diameter...)

[de_Stan]

But i get the same result by just increasing the mass of an object without turning it into a black hole right? Selecting black hole just changes it's size. For example if i turn the Sun into a black hole nothing happerns. I have to increase the mass too. I dont have any knowledge of this so it might sound funny to some of you but i why should i turn the sun into a black hole? Just increase the mass and planets will go for the sun.

This is what i see from the sim but i might miss the main idea..

[Bla]

Black holes in Universe Sandbox are like all other bodies. The only difference is that their density is set so that light cannot escape from its surface. This results in the size of bodies being much more compact, and thus much harder to hit. The objects which pass close by will probably be slingshot away, and this doesn't have to be because the time step is too high.
Universe Sandbox doesn't make the colission with black holes any different than other bodies in the simulation, either. If the combine mode is selected, they will combine (like what I think you're imagining should happen), if bounch mode is enabled they will simply bounch off each other.

In reality, gravity is a force caused by mass, and it doesn't matter whether the mass is a black hole, star or planet. The gravity is dependent on how big the mass is and how far away from it you are. If you turn a star into a black hole, with the same mass, it will not have any effect on any orbits. But because the black hole is much smaller, if a body gets within what would've been the surface of the old star, the gravitational force on that body will be bigger, eventually reaching the point where light can't escape if it gets as close as the surface of the black hole.

I hope what I wrote is correct and useful.

[Joshimitsu91]

But i get the same result by just increasing the mass of an object without turning it into a black hole right? Selecting black hole just changes it's size. For example if i turn the Sun into a black hole nothing happerns. I have to increase the mass too. I dont have any knowledge of this so it might sound funny to some of you but i why should i turn the sun into a black hole? Just increase the mass and planets will go for the sun.

This is what i see from the sim but i might miss the main idea..

As bla said, the only thing that determines whether its a black hole is that the gravity at its surface is so great that light cannot escape. So if its mass is the same its diameter will decrease, and at ranges outside the original star diameter, nothing will change. If you want stuff to be "sucked" towards the sun, you will have to increase the mass, but that is not what happens when a star becomes a black hole.

The objects which pass close by will probably be slingshot away, and this doesn't have to be because the time step is too high.

Objects should tend to orbit the star/black hole if they don't hit it, even if the orbit is very elliptical/large, unless the acceleration is so great that they break away. What i was refering to is that sometimes planets etc. seem to shoot away at very high speed (i've seen mercury at 0.22c), and that is the scenraio which i believe is caused by using too large a time step.

[Dan Dixon]

Black holes in Universe Sandbox are like all other bodies. The only difference is that their density is set so that light cannot escape from its surface. This results in the size of bodies being much more compact, and thus much harder to hit. The objects which pass close by will probably be slingshot away, and this doesn't have to be because the time step is too high.
Universe Sandbox doesn't make the colission with black holes any different than other bodies in the simulation, either. If the combine mode is selected, they will combine (like what I think you're imagining should happen), if bounch mode is enabled they will simply bounch off each other.

In reality, gravity is a force caused by mass, and it doesn't matter whether the mass is a black hole, star or planet. The gravity is dependent on how big the mass is and how far away from it you are. If you turn a star into a black hole, with the same mass, it will not have any effect on any orbits. But because the black hole is much smaller, if a body gets within what would've been the surface of the old star, the gravitational force on that body will be bigger, eventually reaching the point where light can't escape if it gets as close as the surface of the black hole.

I hope what I wrote is correct and useful.

Yes. This is correct (and useful). Thanks.

[Technotica]

And I always thought if something gets too close to a black hole the hole will eat it up (I blame scifi movies and books! )!

[Joshimitsu91]

And I always thought if something gets too close to a black hole the hole will eat it up (I blame scifi movies and books! )!

Well you thought right, you just over estmated their power! Lol

[Dan Dixon]

Read all about them here:
http://en.wikipedia.org/wiki/Black_hole

Or a simpler version:
http://simple.wikipedia.org/wiki/Black_hole

[Jayman0101]

When I create a black hole, i get a message that says "Set the diameter of Earth(for example) so that it's escape velocity equals the speed of light."
 
Help?

[Darvince]

I don't get what you mean. It made the black hole already. It's just telling you what it did.

[Joshimitsu91]

When I create a black hole, i get a message that says "Set the diameter of Earth(for example) so that it's escape velocity equals the speed of light."
 
Help?

Thats basically the definition of a black hole... so its saying "Set the [Earth] to be a Black Hole". All it has done is kept the mass of the Earth the same and reduced its size to that of a black hole of the same mass.

[Teh_Saccade]

When I create a black hole, i get a message that says "Set the diameter of Earth(for example) so that it's escape velocity equals the speed of light."

It's probably easier to understand if you read the message as:
"[Universe Sandbox has] set the diameter of Earth (for example) so that it's escape velocity equals the speed of light."

It is a report, not an instruction for you
Confused me too, first few times.

[Dan Dixon]

It's probably easier to understand if you read the message as:
"[Universe Sandbox has] set the diameter of Earth (for example) so that it's escape velocity equals the speed of light."

Good idea. This change will be in the next update.

[Hegemon54]

I think in the latest version, you said that you added a black hole button?  Where is that?

[Dan Dixon]

you added a black hole button?  Where is that?

Select an object. The button is in the properties panel on the right side of the screen.