Polymerisation of Hydrogen and Helium

How cool does that sound?

It turns out that may just be what’s happening in the middle of White Dwarf stars, based on emission spectra.  Why is that so crazy?  I’m glad you asked.  Well you just can’t make polymer-like chains of hydrogen and helium on Earth; you need a much much [much^n where n is large] higher magnetic field to produce these interactions, dubbed paramagnetic bonding.  Recent modelling from a group consisting of researchers from Norway and the US has been able to shed some light on the mechanism allowing for these molecules.

Artist's rendition of a Neutron Star.  Photo from http://www.dailygalaxy.com/my_weblog/2007/08/astronomers-bel.html.

Artist’s rendition of a Neutron Star. Photo from http://www.dailygalaxy.com/my_weblog/2007/08/astronomers-bel.html.

Earth’s magnetic field is massive.  It protects us from the solar winds.  Without this giant field our atmosphere would likely be just a fraction of the density it is now.  We have a 2000+ kilometre wide core that’s spinning resulting in a dynamo that essentially makes life possible.  OK, so I obviously have a thing for magnetics but get this.

Earth’s field is about 52 microTesla where I live.  Micro as in 10^-6.  The fields in the middle of these White Dwarf stars are ~400,000 Tesla – 4×10^5.  Yeah, that’s 11 orders of magnitude greater.  In Neutron Stars and magnetrons that can be even higher—approximately 10^10 Tesla.  The best we’ve done on Earth is a few hundred Tesla and the generators tear themselves apart nearly instantly.

When we get into magnetic fields this intense, the magnetic interactions become just as important as Coulomb (electrical) interactions.  This means that most of what we know about chemistry on Earth must be completely re-thought for the centres of these stars.

OK, so I also have to admit that my chemistry is piss-poor, and I don’t understand all the implications of paramagnetically-bonded elements.  I will try to relate my rude understanding, and I definitely invite comments and corrections.  Most of my understanding comes from [1] below.

The claims, however, are bold—and according to researcher Mark Hoffman, justified.  This is a totally new bonding mechanism.  Think back to high school chemistry, where we learned about covalent bonding (like what holds ethanol together), and ionic bonding (like what holds table salt together).  (Yes, I am sitting at a bar as I write this.)

Well now we have paramagnetic bonding, where the orbitals of the electrons in the atoms are modified and align with the background field.  This forces atoms to all have an aligned dipole moment, allowing them to bond in a way not unlike Van der Waals forces.

Lange et. al. provides the following schematic:

F1.largeSo, while we can’t observe these interactions directly, their modelling provides the best model so far for how hydrogen and helium can polymerise in the middle of some of the most extreme pseudo-stable environments in the Universe.  That’s pretty cool.

[1] Kai K. Lange et. al., 2012, A paramagnetic bonding mechanism for diatomics in strong magnetic fields, Science, 337, pp 327-331.

[2] http://www.sciencedaily.com/releases/2012/12/121207174415.htm


About faradaysheadache

Research Geophysicist with the US Geological Survey.
This entry was posted in Astronomy, Chemistry, Physics, Science and tagged . Bookmark the permalink.

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