Search Publications
Cobalt-56 γ-ray emission lines from the type Ia supernova 2014J
Sunyaev, R.; Sazonov, S.; Churazov, E. +8 more
A type Ia supernova is thought to be a thermonuclear explosion of either a single carbon-oxygen white dwarf or a pair of merging white dwarfs. The explosion fuses a large amount of radioactive 56Ni (refs 1-3). After the explosion, the decay chain from 56Ni to 56Co to 56Fe generates γ-ray photons, which a…
A luminous, blue progenitor system for the type Iax supernova 2012Z
Foley, Ryan J.; Riess, Adam G.; Kirshner, Robert P. +6 more
Type Iax supernovae are stellar explosions that are spectroscopically similar to some type Ia supernovae at the time of maximum light emission, except with lower ejecta velocities. They are also distinguished by lower luminosities. At late times, their spectroscopic properties diverge from those of other supernovae, but their composition (dominate…
Characterizing and predicting the magnetic environment leading to solar eruptions
Amari, Tahar; Canou, Aurélien; Aly, Jean-Jacques
The physical mechanism responsible for coronal mass ejections has been uncertain for many years, in large part because of the difficulty of knowing the three-dimensional magnetic field in the low corona. Two possible models have emerged. In the first, a twisted flux rope moves out of equilibrium or becomes unstable, and the subsequent reconnection…
H2D+ observations give an age of at least one million years for a cloud core forming Sun-like stars
Caselli, Paola; Menten, Karl M.; Sipilä, Olli +8 more
The age of dense interstellar cloud cores, where stars and planets form, is a crucial parameter in star formation and difficult to measure. Some models predict rapid collapse, whereas others predict timescales of more than one million years (ref. 3). One possible approach to determining the age is through chemical changes as cloud contraction occu…
A massive galaxy in its core formation phase three billion years after the Big Bang
Kirkpatrick, Allison; Franx, Marijn; van Dokkum, Pieter +13 more
Most massive galaxies are thought to have formed their dense stellar cores in early cosmic epochs. Previous studies have found galaxies with high gas velocity dispersions or small apparent sizes, but so far no objects have been identified with both the stellar structure and the gas dynamics of a forming core. Here we report a candidate core in the…
Early turbulent mixing as the origin of chemical homogeneity in open star clusters
Krumholz, Mark R.; Feng, Yi
The abundances of elements in stars are critical clues to stars' origins. Observed star-to-star variations in logarithmic abundance within an open star cluster--a gravitationally bound ensemble of stars in the Galactic plane--are typically only about 0.01 to 0.05 over many elements, which is noticeably smaller than the variation of about 0.06 to 0…
The rarity of dust in metal-poor galaxies
Sandstrom, Karin M.; Bolatto, Alberto D.; Leroy, Adam K. +7 more
Galaxies observed at redshift z>6, when the Universe was less than a billion years old, thus far very rarely show evidence of the cold dust that accompanies star formation in the local Universe, where the dust-to-gas mass ratio is around one per cent. A prototypical example is the galaxy Himiko (z = 6.6), which--a mere 840million years after th…
Stellar feedback as the origin of an extended molecular outflow in a starburst galaxy
Moustakas, J.; Rudnick, G. H.; Krips, M. +6 more
Recent observations have revealed that starburst galaxies can drive molecular gas outflows through stellar radiation pressure. Molecular gas is the phase of the interstellar medium from which stars form, so these outflows curtail stellar mass growth in galaxies. Previously known outflows, however, involve small fractions of the total molecular gas…
The exclusion of a significant range of ages in a massive star cluster
Deng, Licai; de Grijs, Richard; Li, Chengyuan
Stars spend most of their lifetimes on the main sequence in the Hertzsprung-Russell diagram. The extended main-sequence turn-off regions--containing stars leaving the main sequence after having spent all of the hydrogen in their cores--found in massive (more than a few tens of thousands of solar masses), intermediate-age (about one to three billio…
Inefficient star formation in extremely metal poor galaxies
Wang, Junzhi; Gao, Yu; Zhang, Zhi-Yu +5 more
The first galaxies contain stars born out of gas with few or no `metals' (that is, elements heavier than helium). The lack of metals is expected to inhibit efficient gas cooling and star formation, but this effect has yet to be observed in galaxies with an oxygen abundance (relative to hydrogen) below a tenth of that of the Sun. Extremely metal po…