Flash in space: An artist’s view of a gamma-ray burst. Credit: DESY, Science Communication Lab Using the H.E.S.S. observatory, researchers at GRB 190829A observe unusual features that challenge models. Researchers from the H.E.S.S. Collaboration succeeded to derive the intrinsic spectrum of the very-high-energy gamma-ray afterglow emission of a relatively nearby gamma-ray burst. Surprisingly, the gamma-ray spectrum resembles that of the much lower-energy X-rays, while the fading emission from both bands was observed to march in parallel over three nights. These remarkable findings challenge the current emission scenarios. Gamma-ray bursts (GRBs) are bright X-ray and gamma-ray flashes observed in the sky, emitted by distant extragalactic sources. They are associated with the creation or merging of neutron stars or black holes; processes that result in an explosive outburst of material moving incredibly close to the speed of light. The initial flashes, which last a few seconds, are...

An artist’s rendition of the Parker Solar Probe approaching the Sun. Astronomers have used data from Parker, along with data from other solar missions, to detect and study Solar stream interactions. Credit: NASA/Johns Hopkins APL/Steve Gribben  When a fast solar wind stream erupts from a coronal hole (a cooler region in the Sun’s atmosphere) and overtakes a slower moving solar wind stream, a stream interaction region (SIR) can form. In the SIR, a density “pileup” of compressed plasma develops upstream of the interface; typically there is a peak in pressure followed by a rarefaction region in the fast solar wind component. As the SIR propagates away from the Sun, to distances of one astronomical unit or beyond, the compression can form a shock that efficiently accelerates charged particles. Thus SIRs are a major source of energetic particles in interplanetary space. Coronal holes, the main sources of the high-speed stream, rotate as the Sun rotates on its axis, and the SIR structure...

  Galaxies exchange matter with their external environment thanks to galactic winds. The MUSE instrument from the Very Large Telescope has, for the very first time, mapped the galactic wind that drive these exchanges between galaxies and nebulae. This observation led to the detection of some of the Universe’s missing matter. Galaxies can receive and exchange matter with their external environment thanks to the galactic winds created by stellar explosions. Thanks to the MUSE instrument[1] from the Very Large Telescope at the ESO, an international research team, led on the French side by the CNRS and l’Université Claude Bernard Lyon,[1,2] has mapped a galactic wind for the first time. This unique observation, which is detailed in a study published in MNRAS on September 16, 2021, helped to reveal where some of the Universe’s missing matter is located and to observe the formation of a nebula around a galaxy. Galaxies are like islands of stars in the Universe, and possess ordinary or ba...