Denmark the 22 proposals have been agreed upon by a parliamentary majority. Denmark shares strong cultural and historic ties with its Scandinavian neighbours Sweden and Norway. It has historically been one of the most socially progressive cultures in the world. In 1969, Denmark was the first country to legalise pornography, and in 2012, Denmark replaced its "registered partnership" laws, which it had been the first country to introduce in 1989, with gender-neutral marriage. Modesty and social equality are important parts of Danish culture. The astronomical discoveries of Tycho Brahe (1546–1601), Ludwig A. Colding's (1815–88) neglected articulation of the principle of conservation
Planetary nebula the French astronomer Antoine Darquier de Pellepoix described in his observations of the Ring Nebula, "...a very dim but perfectly outlined; it is as large as Jupiter and resembles a fading planet". Whatever the true origin of the term, the label "planetary nebula" became ingrained in the terminology used by astronomers to categorize these types of nebulae, and is still used by astronomers today. Most planetary nebulae form at the end of the star's life, and are a relatively short-lived phenomenon, lasting perhaps a few tens of thousands of years, compared to a typical stellar lifetime spanning several billion years.