Illustration of the method to estimate a comet's size (Image NASA/JPL-Caltech)

An article published in “The Astronomical Journal” describes a research on long-period comets concluding that they’re more common than expected. A team of researchers led by James Bauer of the University of Maryland used data collected by NASA’s WISE Space Telescope to discover that those at least one kilometer (0.6 miles) across are more common than expected and are, on average, twice as large as those of the Jupiter family.

The Fomalhaut system seen by ALMA and Hubble (Image ALMA (ESO/NAOJ/NRAO), M. MacGregor; NASA/ESA Hubble, P. Kalas; B. Saxton (NRAO/AUI/NSF))

Two articles to be published in “The Astrophysical Journal” describe two studies concerning the ring of debris surrounding the star Fomalhaut. An international team of astronomers used the ALMA radio telescope to get the first complete image of those debris, which are probably the product of a series of collisions among comets near the outer edges of that solar system. Carbon monoxide and carbon dioxide have also been found in abundance.

Scheme of the molecular oxygen production process (Image courtesy Caltech)

An article published in the journal “Nature Communications” provides an explanation for the presence of oxygen molecules on the comet 67P/Churyumov-Gerasimenko. Konstantinos Giapis, a chemical engineer at Caltech, conducted this research after noting that the chemical reactions that took place on the comet’s surface were similar to those he had been generating for years. The most likely hypothesis initially offered was that it had “survived” since the solar system’s formation but perhaps the correct explanation has now been found.

Phases of the collapse at Aswan (Image ESA/Rosetta/NavCam – CC BY-SA IGO 3.0; ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA)

Two articles, one published in the journal “Nature Astronomy” and one published in the journal “Science”, describe two studies about the comet 67P/Churyumov-Gerasimenko. The first is about a cliff Aswan in the Seth region of the comet’s nucleus that crumbled. The second article is about the changes that occurred on the comet’s surface detected thanks to ESA’s Rosetta space probe between the summer of 2014 and September 2016.

Dry ice detected with its spectral data and indication of the area (Image Data: ESA/Rosetta/VIRTIS/INAF-IAPS/OBS DE PARIS-LESIA/DLR; Reprinted with permission from G. Filacchione et al., Science 10.1126/science.aag3161 (2016); context image: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0)

Two articles published in the journal “Science” describe the discovery of dry ice, meaning frozen carbon dioxide, on the surface of the comet 67P/Churyumov-Gerasimenko. A team of researchers led by Gianrico Filacchione of the Italian National Institute for Astrophysics and another led by Sonia Fornasier the French LESIA-Observatoire de Paris and Université Paris Diderot used the observations conducted with the VIRTIS spectrometer aboard ESA’s Rosetta space probe to find for the first time dry ice on a comet’s nucleus.