Cold working of sodium metal converts body centred sodium metal to a mixture of a hexagonal form and body centred sodium at 5 K. The hexagonal from converts back to the body-centred form at 100-100 K.
Cold working of lithium metal converts body centred lithium metal to a mixture of a hexagonal form and body centred lithium at 78 K.
Potassium, rubidium, and caesium retain their body centred structure after coolingX-ray study of the alkali metals at low temperatures, , Acta Crystallographica, 08/1956, Volume 9, Issue 8, p.671 - 677, (1956)
Crystal structure of uranium nitride, UN. The structure is face-centered cubic with a lattice constant of 4889 ± 0.001 Å at 26°C and sodium chloride type. The theoretical density is 14315 kg m–3, and the U—N bond distance for coordination number 6 is 2.4449 Å.Crystallographic Data. 177. Uranium Mononitride, , Analytical Chemistry, 01/1959, Volume 31, Issue 1, p.156 - 157, (1959)
Scientists crossed a new frontier in exo-planet research just last year when, using the Hubble Space Telescope, they detected sodium by its characteristic orange colour in the atmosphere of a large alien world orbiting the star HD 209458. Perhaps we are seeing ETs street lighting from a distance?
Beginning in 2006, a new telescope, Kepler (approved recently by NASA) will monitor about 100,000 nearby stars, searching for the slight dimming that occurs when an orbiting planet blocks some of the parent star's light. Because Kepler will be sensitive enough to detect planets as small as Earth, this celestial survey will give scientists an idea of how common Earth-like planets are - and identify candidates for further study.
This space telescope will use a technique called interferometry to dramatically reduce the obscuring glare from the planet's parent star, allowing scientists to see the planet itself, and so perhaps be able to analyse the atmospheres of those planets - required to detect signs of life.