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Early high-resolution images of two 2021 novae reveal eruptions unfolding in multiple stages with colliding outflows that produce shocks and gamma rays, reshaping our understanding of stellar explosions.

Two flat-spectrum radio sources in the Milky Way globular cluster M22 are thought to be accreting stellar-mass black holes; the identification of two black holes in one cluster shows that the ejection of black holes from clusters is not as efficient as predicted by most models.

A type Ia supernova shows the presence of helium-rich circumstellar material, as demonstrated by its spectral features, infrared emission and a radio counterpart, that probably originates from a single-degenerate system in which a white dwarf accretes material from a helium donor star.

Simultaneous optical and gamma-ray observations of nova V906 Carinae reveal correlated flares in both wavelength ranges that can be linked to shocks in the nova ejecta. Weak X-ray emission suggests that the shocks are deeply embedded, but they contribute substantially to the luminosity of the nova.

High-resolution radio imaging of the γ-ray-emitting nova V959 Mon, hosted by a white dwarf and its binary companion, shows that gaseous ejecta are expelled along the poles as a wind from the white dwarf, that denser material drifts out along the equatorial plane, propelled by orbital motion, and that γ-ray production occurs at the interface between these polar and equatorial regions.

A tight correlation between gamma rays and optical emission in nova ASASSN-16ma indicates that the optical light comes from reprocessed emission from shocks in the ejecta, rather than an energy release near the hot white dwarf, as in the standard model.

Accretion onto the surface of a white dwarf typically generates supersoft X-ray emission and broad emission lines due to nuclear fusion. ASASSN-16oh exhibits no visible broad lines, implying there is no surface fusion, and instead, a belt around the dwarf called a spreading layer is the source of the supersoft X-ray emission.