Is that realistic?

[Anthony Sigouin]

I increase the mass of Venus or Earth till it becomes a brown darf than at a particular threshold it becomes all of a sudden a very cold (0.002 K) dark gray star (at about 78 M Jupiter) . I would think that the normal transition would be a red dwarf star?

I give about 6000 times the mass of the sun to the earth and reduce its radius to about 20 km but still no black hole but a star...

Do you have to adjust yourself properly each parameters in relation with each other for the physics to stay realistic?

[bshapiroalbert]

Thanks for asking about this.

When planets transition to stars, they do heat up eventually, but it takes a very long time (hundreds of thousands of years) for the heat to move through the star from its core to its surface, which is why they initially appear to be cold. You can make stars heat up faster by lowering their Surface Heat Capacity under
Temperature > Energy Flow > Surface Heat Capacity

To create a black hole, when you adjust Earth's Mass, you change the Radius calculation to be From Composition to From Density, which locks the objects density. This means that instead of it's Density increasing as you add Mass, it's Radius increases instead.

You can adjust this by pressing the lock button next to the Mass of object after adjusting the mass and then decreasing the radius. That will automatically increase the object's density, causing it to turn into a black hole.

[Anthony Sigouin]

Thank you for your response!

I didn't know for the first point about the black star and I found out myself the second point. It will probably help other people too.

The game is really great, really immersive!

[bshapiroalbert]

Thank you for your kind words, I'm glad to hear your enjoying Universe Sandbox so much. Please do let us know if you have any other questions or issues related to Universe Sandbox.