Over a decade before planets were found orbiting normal stars, the astronomy world was intrigued by the discovery of a vast, edge-on, pancake-flat disk of dust and gas encircling the newborn star Beta Pictoris. It appeared to validate the hypothesis by the German philosopher Immanuel Kant, 230 years ago, that our solar system was born when planets condensed from nebular material in the plane of such a disk. (This model was independently proposed by French scholar Pierre-Simon Laplace in 1796.) Kant regarded the coplanar obits of the planets a fossil skeleton of the long-ago disintegrated disk. Though nearly two dozen circumstellar debris disks have been viewed by the Hubble Space Telescope to date, Beta Pictoris is the first and best example of what a forming young planetary system looks like. That's because it can be seen edge on, and it is the only disk to date where a planet has also been imaged. Hubble has been used to intensively study the disk for the past two decades and this latest picture when compared to previous observations shows that the disk particles appear to smoothly revolve around the star like a majestic carousel. Ground-based telescopes found a Jupiter-sized world embedded in the disk in 2009, and future observations may yield more planetary objects.
Explosive lithium production in the classical nova V339 Del (Nova Delphini 2013)
Nature 518, 7539 (2015). doi:10.1038/nature14161
Authors: Akito Tajitsu, Kozo Sadakane, Hiroyuki Naito, Akira Arai & Wako Aoki
The origin of lithium (Li) and its production process have long been uncertain. Li could be produced by Big Bang nucleosynthesis, interactions of energetic cosmic rays with interstellar matter, evolved low-mass stars, novae, and supernova explosions. Chemical evolution models and observed stellar Li abundances suggest that at least half the Li may have been produced in red giants, asymptotic giant branch (AGB) stars, and novae. No direct evidence, however, for the supply of Li from evolved stellar objects to the Galactic medium has hitherto been found. Here we report the detection of highly blue-shifted resonance lines of the singly ionized radioactive isotope of beryllium, 7Be, in the near-ultraviolet spectra of the classical nova V339 Del (Nova Delphini 2013) 38 to 48 days after the explosion. 7Be decays to form 7Li within a short time (half-life of 53.22 days). The 7Be was created during the nova explosion via the alpha-capture reaction 3He(α,γ)7Be (ref. 5). This result supports the theoretical prediction that a significant amount of 7Li is produced in classical nova explosions.
Astrophysics: A lithium-rich stellar explosion
Nature 518, 7539 (2015). doi:10.1038/518307a
Authors: Margarita Hernanz
The contribution of explosions known as novae to the lithium content of the Milky Way is uncertain. Radioactive beryllium, which transforms into lithium, has been detected for the first time in one such explosion. See Letter p.381