Neptune is a Girl's Best Friend

This was announced a few weeks ago but I missed it and it is pretty cool. An article appeared in the January issue of Nature Physics talking about the possibility of diamonds inside Uranus and Neptune. J.H. Eggert and his team at Lawrence Livermore Labs used a laser to melt a diamond at a pressure of 40 million atmospheres (1 atmosphere is the air pressure at sea level on Earth). They slowly decreased the pressure and temperature. At about 11,000 atmospheres and 50,000 degrees, they found solid diamonds form!

Now here's my favorite part...the solid diamond floated! Usually, solids are more dense the the liquid form of a substance. Water is a notable exception (ice floats because it is less dense). Turns out diamonds have the same property. It makes sense when I thought about it...the crystal structure of diamond holds the carbon atoms fairly far apart, so the density is lower. The trick is it is hard to liquify carbon and measure its properties which they finally did.

This experiment simulated the conditions deep under the cloud tops of Uranus and Neptune. The idea put forth in this paper is that there is a possibility that there is liquid carbon which diamond "icebergs" floating in it. Now that is hard to imagine...I am still trying to wrap my head around that one!

This is all very preliminary and a lot more work needs to be done. This work is a nice example of how we can study distant planets by combining computer simulations and laboratory experiments here on Earth...and I so going to use diamond as another example of a substance that has a lower density in its solid state.

Aren't you glad I didn't use the name of the "other" planet in this blog title?

Reprinted with permission from the Half-Astrophysicist Blog.