# Where is the materials of comet after it crashed into the sun?

If a comet crashes into the sun, where will the substance (eg: water,silicon) be? Will they be inside the sun? Or they will be ejected from sun again?

• Some ancient star-hitting comets have ended up in your head and is now thinking about it. – LocalFluff Feb 2 '16 at 11:09

It depends on the size of the comet. If it's only $0.1$–$1\,\mathrm{km}$, it will evaporate before even reaching the Sun (Li. et al. 2013; Knight & Walsh 2013), and the released gasses will be ejected by the Sun's radiation pressure. Larger comets, so-called Sungrazing comets, can survive close passages, although they probably will be torn apart by tidal forces.
If the comet comes so close that it crashes into the Sun (I'm not sure this has ever been observed, despite various blogs discussing this, but there's no reason it couldn't happen), it would reach the escape velocity of the Sun, i.e. $\sqrt{2 G M_\odot / R_\odot}\sim600\,\mathrm{km}\,\mathrm{s}^{-1}$. This New Scientist article claims that the impact would cause an explosion and possibly a coronal mass ejection, but the underlying scientific article by Brown et al. (2015) seems to indicate that the large ablation of the comet will result in less dramatic velocities.
• Your last sentence needs more precision/deletion. The Sun should end up as a $0.5 M_{\odot}$ white dwarf; the minority of that mass loss will occur during the planetary nebula phase, which occurs right at the end of the Sun's "normal" life, not when it becomes a red giant. – ProfRob Feb 2 '16 at 9:07