predictions. Studies of young radio pulsars and the remarkable magnetar subclass have revealed that as many as 1 in 10 neutron stars, which have descended from normal stars, are born with magnetic fields that exceed 1014 times that of our Sun. What sets this fraction, and whether or not the birth of these highly magnetic neutron stars visibly alters the supernova event, are being actively investigated. Progress here will depend on large surveys of supernovae as well as continued radio and X-ray pulsar observations. The most rapidly rotating neutron stars appear to spin on their axes about once every 1½ milliseconds, by accreting material from a rapidly rotating disk of matter donated from a companion star. However, ever more sensitive radio pulsar surveys continue to find that the maximum spin rate observed is surprisingly less than the maximum possible value, leading to the speculative suggestion that gravitational wave emission regulates the maximum rate. This hypothesis is testable with Advanced LIGO.

The Chemistry of the Universe

Many astrophysical processes exhibit rich chemical signatures and products. The cycle of matter in our galaxy proceeds from the expulsion of matter into interstellar space from dying stars, where it undergoes chemical transformations and eventual incorporation into diffuse clouds and dense molecular clouds. Well over 140 molecules, rich in organic material, have been detected in the interstellar medium by radio, microwave, and infrared techniques, and this is almost certainly the tip of the interstellar chemical iceberg (Figure 2.13). Thanks to the diverse range of interstellar energy sources and environments to which such molecules are exposed, we have the opportunity with ALMA and SOFIA to study fundamentals of chemistry under conditions we cannot create here on Earth.

ALMA will greatly increase our ability to probe the chemistry of nearby galaxies. On a cosmological scale, the chemistry of the primordial elements hydrogen, helium, and lithium was surprisingly rich and dictated the early-universe interactions between matter and radiation. Molecular hydrogen was possibly crucial in forming the first stars after recombination, and studies of redshifted spectra of neutral atomic hydrogen may provide information concerning molecular hydrogen by observing density inhomogeneities. Observations of molecular spectra can give us unique probes of the density, temperature, and kinematics of regions where stars and planets are formed. Exploration of the chemistry in high-redshift galaxies is a current challenge that, as it is met, will provide us with a picture of the evolution of molecular reactions and species across cosmological time.

Tracing the history of organic molecules through their cycles of formation, modification, destruction, and reformation often on the surfaces of tiny dust grains within molecular clouds to their incorporation in planetary systems is important



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