# If a hot Jupiter collides with the parent star, does it enhance or reduce the life of the star?

Suppose a hot Jupiter is collided into parent star due to tidal force, does the life of the star becomes longer due to extra hydrogen, or becomes shorter due to extra mass?

• Is the life of massive stars in general longer due to the extra hydrogen, or shorter due to the extra mass? – pela Jul 14 '16 at 8:43
• If they're roughly the same metallicity then I would say the extra mass causes the star to burn slightly quicker, but I would add that this is probably negligible over the lifetime of the star itself. – Dean Jul 14 '16 at 9:21
• Quicker would be my answer too. More mass = shorter stellar lifespan. That's a general rule with stars. – userLTK Jul 14 '16 at 12:51

The basic rule here being that core temperatures are dictated by the gravity well of the star, which is dictated by the mass (and a few other GR contributions, but usually predominantly mass). The more mass, the deeper the well. So adding more mass just means the core (and areas near it) are in a deeper gravity well, meaning the temperatures go up. Stellar fusion reaction rates are approximately non-linear polynomials in the temperature; some go as far as being proportional to $T^{40}$, the 40-th power of the temperature! It's this non-linearity which results in the fundamental relation of the short answer: more mass equals shorter life. Increasing the mass by a given proportion increases the fusion rates by a (much) larger proportion.