June 2023

The Dragon cargo spacecraft departing the International Space Station to end its CRS-28 mission (Image NASA TV)

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A little while ago, SpaceX’s Dragon spacecraft ended its CRS-28 (Cargo Resupply Service 28) mission for NASA splashing down smoothly off the Florida Coast. The Dragon left the International Space Station about 22 hours earlier. For SpaceX, this was the 8th mission of the 2nd contract with NASA to transport supplies to the Station with the new version of the Dragon cargo spacecraft.

Shortly after the splashdown, SpaceX’s recovery ship went to retrieve the Dragon to transport it to the coast. The cargo brought back to Earth will be delivered to NASA within a few hours. The Dragon spacecraft reached the International Space Station on June 6, 2023.

Diagram of Earth as a detection center for very low-frequency gravitational waves emitted by pairs of supermassive black holes (top) using pulsars (bottom) (Image courtesy EPTA)

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A series of articles published or being published in the journals “Astronomy and Astrophysics” and “The Astrophysical Journal Letters” reports various aspects of the detection of very low-frequency gravitational waves. Researchers from the European Pulsar Timing Array (EPTA), the Indian Pulsar Timing Array (InPta), the Parkes Pulsar Timing Array (PPTA), the Chinese Pulsar Timing Array (CPTA), and the North American Nanohertz Observatory for Gravitational Waves (NanoGrav) analyzed data collected over the course of more than 25 years using groups of pulsars to obtain a kind of detector of gravitational waves at the galactic level. This was possible by exploiting the extreme regularity of the signals emitted by pulsars to detect variations of less than a millionth of a second and their correlations to identify gravitational waves. This technique expands the gravitational-wave astronomy opened up by the LIGO and Virgo detectors since the announcement of the first detection in February 2016.

The nebula Sh2-284 (Image ESO/VPHAS+ team. Acknowledgement: CASU)

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An image captured by the OmegaCAM instrument mounted on ESO’s VST in Chile shows details of the nebula cataloged as Sh2-284. It’s part of the VST Photometric Hα Survey of the Southern Galactic Plane and Bulge (VPHAS+), a survey that included over 500 million objects in the Milky Way to improve our understanding of stars’ life cycles. Sh2-284 is a sort of star nursery whose shape was compared to that of a cat’s face and for this nicknamed “smiling cat”.

The movement of exoplanet AF Lep b, identified in the white spot near the arrows, in images captured in December 2021 and February 2023

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An article published in “Astrophysical Journal Letters” reports the role of the astrometric technique in the discovery of one of the least massive planets so far photographed directly. A team of researchers used the Keck II telescope at the Keck Observatory in Hawaii to photograph the exoplanet cataloged AF Lep b, among the first discovered using the technique of astrometry, which is usually used in conjunction with other astronomical investigation methods. This offers new perspectives in the search for exoplanets.

The area surrounding Sagittarius A* (Image IXPE: NASA/MSFC/F. Marin et al; Chandra: NASA/CXC/SAO; Image Processing: L.Frattare, J.Major & K.Arcand)

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An article published in the journal “Nature” reports evidence that about 200 years ago, Sagittarius A*, or simply Sgr A*, the supermassive black hole at the center of the Milky Way, had a period of intense activity during which it swallowed considerable amounts of gas and dust. A team of researchers led by Frédéric Marin of the Astronomical Observatory of Strasbourg, France, used in particular data collected by the IXPE space telescope to examine the polarization of X-ray light emitted by bright large molecular clouds close to Sgr A*. The conclusion is that their out-of-normal brightness must have been due to the fact that they are reflected emissions produced by some kind of powerful and short-lived flare of the supermassive black hole that occurred about 200 years ago.