DirtyBlackRussian

.@ESA_Euclid space telescope has discovered 31 quasars from the early Universe, including the two most distant quasars identified to date. These remarkable objects were already shining when the Universe was less than 800 million years old, offering astronomers a rare opportunity to investigate how supermassive black holes formed and evolved during the earliest stages of cosmic history. Quasars are extraordinarily luminous galactic nuclei powered by matter falling towards supermassive black holes. As gas spirals inward, it becomes extremely hot and releases enormous amounts of radiation, sometimes outshining the entire galaxy surrounding it. Their extraordinary brightness allows astronomers to detect them across billions of light-years. Among Euclid's discoveries, 12 quasars have redshifts of 7 or greater. Two are particularly remarkable: EUCL J172902.75+641018.1, with a redshift of 7.77, and EUCL J125308.55+705432.3, at 7.69. Their light began its journey when the Universe was approximately 670 million years old. These objects existed during the epoch of reionization, when radiation from the first generations of stars and galaxies was transforming the intergalactic medium. The discoveries were made using observations covering approximately 3,000 square degrees of sky. Researchers combined Euclid's visible and near-infrared observations with machine-learning and probabilistic selection techniques, followed by spectroscopic observations from ground-based telescopes to confirm the candidates. What makes these results particularly valuable is Euclid's ability to identify relatively faint quasars that previous surveys struggled to detect. Its enormous survey area, sensitivity and infrared capabilities are expanding our understanding of the early quasar population. The central question remains how black holes could grow to enormous masses so soon after the Big Bang. By identifying a larger and more diverse population of ancient quasars, Euclid provides new observational constraints on their formation, accretion histories and the evolution of their host galaxies. Although Euclid was primarily designed to investigate dark matter, dark energy and the large-scale structure of the Universe, its observations are also becoming an important resource for exploring the earliest chapters of cosmic history. 🍁 aanda.org/articles/aa/full_h…

When the @ehtelescope Horizon Telescope released its first image of M87* in 2019, the most striking feature was a bright ring surrounding a dark centre. The glow comes from hot plasma close to the black hole, about 55 million light-years away. Its gravity bends the light on its way to us and captures some of it, leaving a shadow against the surrounding glow. An independent team has now returned to the telescope measurements to ask how much of that familiar shape the data can actually pin down. The question arose from the way the image was made. Radio telescopes on different continents observed M87* at the same time. Each pair recorded information about structure on a particular scale and in a particular direction. The gaps between those measurements leave room for more than one image to fit the data. In one earlier reanalysis, changing the size of the patch of sky being reconstructed was enough to produce an elongated bright patch where the ring had been. Samuel Lai and colleagues at Australia’s @CSIRO took a different approach. They combined the signals in a way that cancels out calibration errors introduced at individual telescopes while preserving information about the shape of the source. Their algorithm had no ring built into it. Yet when they applied it to the original observations, a ring emerged around a dark centre, measuring 42.2 ± 1.5 microarcseconds across. At M87’s distance, that diameter is consistent with a black hole about 6.5 billion times as massive as the Sun. The finer details, including exactly where the plasma appears brightest, are still harder to recover. What now stands on firmer ground is what most of us remember from that first image. A different team, working from the same measurements with a different method, recovered both the ring and its size. 🍁 nature.com/articles/s41586-0…