# What happens to the momentum of a star as its mass is converted to energy? [closed]

Stars move relative to many frames of reference. We can use the CBR for this question, I suppose, but it may not matter. Their momentum p=mass x velocity.

Stars lose mass as it is converted to energy. Percentage-wise it isn't much, but it is tons per second, so it isn't negligible. What happens to the momentum of the star as it loses mass? Presumably it is conserved, so does the velocity of the star increase? Or does the overall system carry off some momentum with the energy, leaving the stellar velocity constant?

• This contains far too many questions. I'll answer the main one. – Rob Jeffries Nov 6 '17 at 2:00
• This would apply to any hot object that radiates heat in all directions, not just stars. It's an interesting application to conservation of energy that I'd never considered. Ultimately I think the problem can be simplified by taking a moving object and imagining two photons flying off it in opposite directions. From any frame of reference the photon traveling in the direction of the object would carry with it more energy and more momentum. The speed should remain unchanged given equal photon emissions in opposite directions, but doing the math would be an interesting exercise. – userLTK Nov 6 '17 at 3:08
• As Rob implied, please edit your text down to the main question. – Jan Doggen Nov 6 '17 at 8:56