Juno catches an escaping ion as new telescopes target atmospheres and early black holes
Juno measured an ion escaping Jupiter's aurora in place, a 900-telescope design targets Earth-like atmospheres in one transit, and Webb found the closest confirmed early black-hole pair.
Science··Midday
Juno measures an ion escaping the aurora in place
Particle instruments on the Juno spacecraft have detected the trihydrogen cation directly in place in Jupiter's auroral region for the first time, rather than by remote sensing. Jian-zhao Wang and colleagues report the result in Nature Astronomy. The ion is produced in hydrogen-rich planetary atmospheres by solar radiation and particle impacts and is treated as a key diagnostic of atmospheric energy balance. At Jupiter it forms most efficiently in the auroral region, where electrons rain down. Until now its properties could be inferred only from infrared emission integrated along the line of sight, with limited altitude resolution. Juno caught the ion far above the ionosphere and measured intermittent outflows faster than the planet's escape speed. In the authors' proposed mechanism, the outflow begins in the auroral upward electric current region through plasma-wave interactions and is then accelerated by the electric potential above the ionosphere. The reported loss rate is of order ten to the twenty-sixth per second. Similar mechanisms may work at other planets with infrared aurorae and strong magnetic fields.[1]
Nine hundred small telescopes aim at Earth-like air in one transit
To read weaker signatures in nearby planetary atmospheres, Jian Ge and colleagues at the Shanghai Astronomical Observatory propose an array of 900 space telescopes, each with a one-metre aperture, working together. The combined collecting area matches a single 30-metre mirror; the James Webb telescope's mirror is 6.5 metre. The proposal is posted as a preprint on arXiv, has not been peer reviewed, and gives no cost for the array. In the design, called Life 2.0, each telescope carries its own miniature spectrograph and very low-noise detector, observes the transit independently, is calibrated on its own, and the spectra are combined afterwards. The team calculates that this arrangement could detect atmospheric signatures at about one part per million in Earth twins passing in front of Sun-like stars, including oxygen, ozone and water vapour, in a single annual transit. Target candidates would come from the PLATO and Earth 2.0 missions. Ge's team includes researchers in China and Spain. The proposal rests on splitting the same collecting area across many small, individually cheap craft instead of launching one giant mirror.[2]
Webb separates the closest confirmed early black-hole pair
On a more distant scale the James Webb telescope has separated two supermassive black holes about 4,900 light years apart inside a merging galaxy in a system called LID-1166. Hyewon Suh of the International Gemini Observatory and NSF NOIRLab and colleagues used the near-infrared spectrograph NIRSpec to find two compact sources, both carrying the spectral signature of gas swirling at high speed, the mark of a feeding black hole. ALMA data from the Atacama showed pools of cold gas around each nucleus. The system first drew attention as a strong X-ray source in the Chandra COSMOS Legacy survey but stayed invisible even in the deepest Hubble images. The pair is the narrowest confirmed this early, when the universe was about 1.3 billion years old; the finding was posted as a preprint and accepted by Nature Astronomy. Other candidate pairs from even earlier epochs had separations of tens of thousands of light years. Anna Trindade Falcão of NASA's Goddard Space Flight Center, who was not involved, says the second source stayed in place when the galaxy's light was subtracted by several methods, which is meaningful evidence, yet detailed follow-up is still needed to rule out one black hole plus leftover glow. Juno's ion, the 900-telescope design and Webb's pair put efforts to catch weak signals — in place, with many small instruments, or with a new spectrograph — on the same agenda.[3], [1], [2]
