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This article reviews the developments on the topic of so-called changing-look active galactic nuclei from the past ten years or so. These active galactic nuclei show dramatic flux and spectral changes at X-ray, ultraviolet and optical wavelengths, due to either obscuration or changes in accretion rate.
Prolonged radio emissions above a sunspot, akin to those auroral emissions previously seen in the polar regions of planets and certain stars, have been detected using the Very Large Array. This detection could potentially provide support for an alternative mechanism for the origin of some stellar radio bursts.
Juno’s global infrared mapping of Jupiter’s moon Io determined the distribution as well as the energy output of its volcanoes. Spatial differences emerge, with the equator more active than the polar zones and more heat flow at the north pole than at the south, indicative of an uneven lithosphere.
Extremely low-mass stars, much less massive than the Sun, lack radiative cores—something that could affect their magnetic dynamos. This study reveals that these stars can have magnetic fields that are up to 30% stronger than those of Sun-like stars, implying fundamental differences in their internal magnetic structures.
ESA’s Trace Gas Orbiter reveals that the winter night sky on Mars emits visible light between 50 km and 70 km altitude in the polar regions. This nightglow should be observable with simple space camera systems and the naked eyes of future Mars astronauts.
Theories predict that core asphericity must be involved in core-collapse supernova explosions; however, the shape of these explosions has not been directly observed. The distribution of the explosive burning ash has now been revealed using nebular spectroscopy, indicating that a collimated structure is common in many stellar explosions.
A lensed quasar at redshift z ≈ 10.3, seen in X-rays, hosts a supermassive black hole of mass similar to that of its host galaxy. The large black-hole mass at a young age, as well as the amount of X-rays it produces, suggest that the black hole formed from the collapse of a huge cloud of gas.
High-resolution observations using a network of ground-based radio dishes and one telescope in space have revealed filamentary structures in the source 3C279. These filaments may explain the origin of radio variability in blazar jets.
The altered and thermally metamorphosed CY chondrites are shown to be the meteoritic analogue of asteroid Phaethon. This suggests that Phaethon’s activity is driven by gas released from the decomposition of near-surficial material heated at perihelion, whereas the interior is kept relatively unaltered and hydrated.
Juno’s close flyby of Ganymede on 7 June 2021 allowed the infrared mapping spectrometer JIRAM to observe the surface at unprecedented spatial resolution. JIRAM’s detailed spectroscopic characterization reveals past extensive aqueous alteration on the moon, possibly together with hydrothermal activity.
Late-phase spectroscopy reveals that explosive nucleosynthesis, occurring in a bipolar collimated configuration, is commonly found for core-collapse supernovae, highlighting the importance of asphericity in shaping these diverse cosmic fireworks.
Venus’s atmosphere is linked to its interior and can be used to infer the planet’s evolution. Observed atmospheric N2, CO2 and surface pressures are best explained by an early phase of plate tectonics, operating for at least 1 billion years.
Space interferometry reveals the hidden and filamentary internal structure of the relativistic jet in 3C 279 at microarcsecond angular resolution. These details challenge previous assumptions on the morphology and radio variability of blazars.
Using NASA’s Juno mission measurements, researchers obtain a new high-precision map of Jupiter’s gravity field and confirm that the planet’s observed strong east–west jet streams penetrate inwards in a direction parallel to the planet’s spin axis.
New northern aurora emissions on Uranus in the infrared spectrum are detected after a 30-year search. The emissions, observed close to equinox, are most likely caused by the 88% increase in upper atmosphere column density.
Fast radio bursts, arriving at Earth from distant galaxies, usually have durations of a few milliseconds or more. Now, data on a source of repeating fast radio bursts have been revisited, with much higher time resolution than before, and burst signals are seen that last only a few microseconds — showing that the properties of fast radio bursts are more diverse than previously thought.
