Formation of new stellar populations from gas accreted by massive young star clusters
Nature 539, 7627 (2016). doi:10.1038/nature19336
Author: Chengyuan Li, Richard de Grijs, Licai Deng, Aaron M. Geller, Yu Xin, Yi Hu & Claude-André Faucher-Giguère
Nature529, 502–504 (2016); doi:10.1038/nature16493Following publication of this Letter, we were made aware that the target cluster identified as ‘NGC 1696’ is instead the cluster ‘NGC 1806’. This mistake was caused by a misidentification in the Hubble
The formation of Charon’s red poles from seasonally cold-trapped volatiles
Nature 539, 7627 (2016). doi:10.1038/nature19340
Authors: W. M. Grundy, D. P. Cruikshank, G. R. Gladstone, C. J. A. Howett, T. R. Lauer, J. R. Spencer, M. E. Summers, M. W. Buie, A. M. Earle, K. Ennico, J. Wm. Parker, S. B. Porter, K. N. Singer, S. A. Stern, A. J. Verbiscer, R. A. Beyer, R. P. Binzel, B. J. Buratti, J. C. Cook, C. M. Dalle Ore, C. B. Olkin, A. H. Parker, S. Protopapa, E. Quirico, K. D. Retherford, S. J. Robbins, B. Schmitt, J. A. Stansberry, O. M. Umurhan, H. A. Weaver, L. A. Young, A. M. Zangari, V. J. Bray, A. F. Cheng, W. B. McKinnon, R. L. McNutt, J. M. Moore, F. Nimmo, D. C. Reuter & P. M. Schenk
A unique feature of Pluto’s large satellite Charon is its dark red northern polar cap. Similar colours on Pluto’s surface have been attributed to tholin-like organic macromolecules produced by energetic radiation processing of hydrocarbons. The polar location on Charon implicates the temperature extremes that result from Charon’s high obliquity and long seasons in the production of this material. The escape of Pluto’s atmosphere provides a potential feedstock for a complex chemistry. Gas from Pluto that is transiently cold-trapped and processed at Charon’s winter pole was proposed as an explanation for the dark coloration on the basis of an image of Charon’s northern hemisphere, but not modelled quantitatively. Here we report images of the southern hemisphere illuminated by Pluto-shine and also images taken during the approach phase that show the northern polar cap over a range of longitudes. We model the surface thermal environment on Charon and the supply and temporary cold-trapping of material escaping from Pluto, as well as the photolytic processing of this material into more complex and less volatile molecules while cold-trapped. The model results are consistent with the proposed mechanism for producing the observed colour pattern on Charon.
Bridge the planetary divide
Nature 539, 7627 (2016). doi:10.1038/539025a
Authors: Ariel D. Anbar, Christy B. Till & Mark A. Hannah
To explain why our planet is habitable, geoscientists studying Earth’s surface and interior must work with each other and with communications scholars, write Ariel D. Anbar, Christy B. Till and Mark A. Hannah.
Astronomy: Small stars host water worlds
Nature 539, 7627 (2016). doi:10.1038/539008d
Earth-sized planets covered in water may be abundant around red dwarfs, the most common type of star in the Universe.Yann Alibert and Willy Benz at the University of Bern used computer simulations to predict the properties of planets that could form around red dwarfs
In writer Edgar Allan Poe's short story "The Tell-Tale Heart," a killer confesses his crime after he thinks he hears the beating of his victim's heart. The heartbeat turns out to be an illusion. Astronomers, however, discovered a real "tell-tale heart" in space, 6,500 light-years from Earth. The "heart" is the crushed core of a long-dead star, called a neutron star, which exploded as a supernova and is now still beating with rhythmic precision. Evidence of its heartbeat are rapid-fire, lighthouse-like pulses of energy from the fast-spinning neutron star. The stellar relic is embedded in the center of the Crab Nebula, the expanding, tattered remains of the doomed star.
Potassium isotopic evidence for a high-energy giant impact origin of the Moon
Nature 538, 7626 (2016). doi:10.1038/nature19341
Authors: Kun Wang & Stein B. Jacobsen
The Earth–Moon system has unique chemical and isotopic signatures compared with other planetary bodies; any successful model for the origin of this system therefore has to satisfy these chemical and isotopic constraints. The Moon is substantially depleted in volatile elements such as potassium compared with the Earth and the bulk solar composition, and it has long been thought to be the result of a catastrophic Moon-forming giant impact event. Volatile-element-depleted bodies such as the Moon were expected to be enriched in heavy potassium isotopes during the loss of volatiles; however such enrichment was never found. Here we report new high-precision potassium isotope data for the Earth, the Moon and chondritic meteorites. We found that the lunar rocks are significantly (>2σ) enriched in the heavy isotopes of potassium compared to the Earth and chondrites (by around 0.4 parts per thousand). The enrichment of the heavy isotope of potassium in lunar rocks compared with those of the Earth and chondrites can be best explained as the result of the incomplete condensation of a bulk silicate Earth vapour at an ambient pressure that is higher than 10 bar. We used these coupled constraints of the chemical loss and isotopic fractionation of K to compare two recent dynamic models that were used to explain the identical non-mass-dependent isotope composition of the Earth and the Moon. Our K isotope result is inconsistent with the low-energy disk equilibration model, but supports the high-energy, high-angular-momentum giant impact model for the origin of the Moon. High-precision potassium isotope data can also be used as a ‘palaeo-barometer’ to reveal the physical conditions during the Moon-forming event.
Icy heart could be key to Pluto’s strange geology
Nature 538, 7626 (2016). http://www.nature.com/doifinder/10.1038/nature.2016.20856
Author: Alexandra Witze
NASA’s New Horizons mission plumbs complex interplay between the dwarf planet's surface and its sky.
Astrophysics: Birth of stellar siblings
Nature 538, 7626 (2016). doi:10.1038/538466a
Authors: Adele Plunkett
Binary and multiple star systems result from the fragmentation of dense material in young molecular clouds. Observations reveal that this can occur on small scales, supporting a previous model of star formation. See Letter p.483
A triple protostar system formed via fragmentation of a gravitationally unstable disk
Nature 538, 7626 (2016). doi:10.1038/nature20094
Authors: John J. Tobin, Kaitlin M. Kratter, Magnus V. Persson, Leslie W. Looney, Michael M. Dunham, Dominique Segura-Cox, Zhi-Yun Li, Claire J. Chandler, Sarah I. Sadavoy, Robert J. Harris, Carl Melis & Laura M. Pérez
Binary and multiple star systems are a frequent outcome of the star formation process and as a result almost half of all stars with masses similar to that of the Sun have at least one companion star. Theoretical studies indicate that there are two main pathways that can operate concurrently to form binary/multiple star systems: large-scale fragmentation of turbulent gas cores and filaments or smaller-scale fragmentation of a massive protostellar disk due to gravitational instability. Observational evidence for turbulent fragmentation on scales of more than 1,000 astronomical units has recently emerged. Previous evidence for disk fragmentation was limited to inferences based on the separations of more-evolved pre-main sequence and protostellar multiple systems. The triple protostar system L1448 IRS3B is an ideal system with which to search for evidence of disk fragmentation as it is in an early phase of the star formation process, it is likely to be less than 150,000 years old and all of the protostars in the system are separated by less than 200 astronomical units. Here we report observations of dust and molecular gas emission that reveal a disk with a spiral structure surrounding the three protostars. Two protostars near the centre of the disk are separated by 61 astronomical units and a tertiary protostar is coincident with a spiral arm in the outer disk at a separation of 183 astronomical units. The inferred mass of the central pair of protostellar objects is approximately one solar mass, while the disk surrounding the three protostars has a total mass of around 0.30 solar masses. The tertiary protostar itself has a minimum mass of about 0.085 solar masses. We demonstrate that the disk around L1448 IRS3B appears susceptible to disk fragmentation at radii between 150 and 320 astronomical units, overlapping with the location of the tertiary protostar. This is consistent with models for a protostellar disk that has recently undergone gravitational instability, spawning one or two companion stars.