Confirmation of C60+ in the interstellar medium

Confirming interstellar C+60 using the Hubble Space Telescope

Recent advances in laboratory spectroscopy lead to the claim of ionized Buckminsterfullerene (C60+) as the carrier of two diffuse interstellar bands (DIBs) in the near-infrared. However, irrefutable identification of interstellar C60+ requires a match between the wavelengths and the expected strengths of all absorption features detectable in the laboratory and in space. Here we present Hubble Space Telescope (HST) spectra of the region covering the C60+ 9348, 9365, 9428 and 9577 {\AA} absorption bands toward seven heavily-reddened stars. We focus in particular on searching for the weaker laboratory C60+ bands, the very presence of which has been a matter for recent debate. Using the novel STIS-scanning technique to obtain ultra-high signal-to-noise spectra without contamination from telluric absorption that afflicted previous ground-based observations, we obtained reliable detections of the (weak) 9365, 9428 {\AA} and (strong) 9577 {\AA} C60+ bands. The band wavelengths and strength ratios are sufficiently similar to those determined in the latest laboratory experiments that we consider this the first robust identification of the 9428 {\AA} band, and a conclusive confirmation of interstellar C60+.

http://arxiv.org/abs/1904.08821

Astrophysical detection of the helium hydride ion

Primordial molecule detected in space for the first time

Within 100,000 years of the Big Bang, the very first molecule emerged, an improbable marriage of helium and hydrogen known as a helium hydride ion, or HeH⁺. "It was the beginning of chemistry," said David Neufeld, a professor at John's Hopkins University and co-author of a study published Wednesday detailing how—after a multi-decade search—scientists finally detected the elusive molecule in space. Theoretical models had long since convinced astrophysicists that HeH⁺ came first, followed—in a precise order—by a parade of other increasingly complex and heavy molecules.
HeH⁺ had also been studied in the laboratory, as early as 1925.

https://phys.org/news/2019-04-elusive-molecule-universe-space.html

Brown dwarfs formed in a protoplanetary disk?

Are brown dwarfs failed stars or super-planets? 

Brown dwarfs fill the "gap" between stars and the much smaller planets—two very different types of astronomical objects. But how they originate has yet to be fully explained. Astronomers from Heidelberg University may now be able to answer that question. They discovered that the star ν Ophiuchi in the Milky Way is being orbited by two brown dwarfs, which in all probability formed along with the star from a gas and dust disk, just as planets do.

https://phys.org/news/2019-04-brown-dwarfs-stars-super-planets.html

Discovery of a nearby stellar stream in Gaia DR2

Extended stellar systems in the solar neighborhood - II. Discovery of a nearby 120° stellar stream in Gaia DR2

We report the discovery of a large, dynamically cold, coeval stellar stream that is currently traversing the immediate solar neighborhood at a distance of only 100 pc. The structure was identified in a wavelet decomposition of the 3D velocity space of all stars within 300 pc to the Sun. Its members form a highly elongated structure with a length of at least 400 pc, while its vertical extent measures only about 50 pc. Stars in the stream are not isotropically distributed but instead form two parallel lanes with individual local overdensities, that may correspond to a remnant core of a tidally disrupted cluster or OB association. Its members follow a very well-defined main sequence in the observational Hertzsprung-Russell diagram and also show a remarkably low 3D velocity dispersion of only 1.3 km/s. These findings strongly suggest a common origin as a single coeval stellar population.

http://arxiv.org/abs/1901.06387