Organic composition of C/1999 S4 (LINEAR): a comet formed near Jupiter?

In the current paradigm, Oort cloud comets formed in the giant planets' region of the solar nebula, where temperatures and other conditions varied greatly. The measured compositions of four such comets (Halley, Hyakutake, Hale-Bopp, and Lee) are consistent with formation from interstellar ices in the cold nebular region beyond Uranus. The composition of comet C/1999 S4 (LINEAR) differs greatly, which suggests that its ices condensed from processed nebular gas, probably in the Jupiter-Saturn region. Its unusual organic composition may require reevaluation of the prebiotic organic material delivered to the young Earth by comets.

An extragalactic supernebula confined by gravity.

Little is known about the origins of globular clusters, which contain hundreds of thousands of stars in a volume only a few light years across. Radiation pressure and winds from luminous young stars should disperse the star-forming gas and disrupt the formation of the cluster. Globular clusters in our Galaxy cannot provide answers; they are billions of years old. Here we report the measurement of infrared hydrogen recombination lines from a young, forming super star cluster in the dwarf galaxy NGC5253. The lines arise in gas heated by a cluster of about one million stars, including 4,000-6,000 massive, hot 'O' stars. It is so young that it is still enshrouded in gas and dust, hidden from optical view. The gases within the cluster seem bound by gravity, which may explain why the windy and luminous O stars have not yet blown away those gases. Young clusters in 'starbursting' galaxies in the local and distant Universe may also be gravitationally confined and cloaked from view.