If we ever make contact with an alien civilization, how will we understand what they’re saying? That’s the question that preoccupies John Elliott of...
Each year, the American Astronomical Society (AAS) hosts two big meetings in January and June that span all of astronomy and its subfields of cosmology, helioastronomy, and planetary science. The COVID-19 pandemic took its toll, beginning in June 2020, when the meeting format pivoted to online presentations. The January 2022 meeting was canceled outright, but by June 2022, the society pivoted again, offering a hybrid mix of in-person and online formats. These two meetings underscored the unquenchable thirst for astronomical questing among our veteran and rising scientists. Here are a few highlights from these meetings.
The formula for collisional excitation of the atoms responsible for auroral emission can explain why green auroras from excited oxygen atoms can occur at relatively low altitudes, but red auroras from these same atoms are constrained to higher altitudes of lower density. The same formula also suggests much lower electron velocities (~100 km/s) than are required to excite the oxygen atoms to the required metastable levels for subsequent emission (~1000 km/s).
Fast Radio Bursts are flashes of radio emission lasting for several milliseconds. The time of arrival of signals depends on the radio frequency, called the dispersion measure (DM), which depends on the environment through which the signals travel, specifically the number of free electrons in their path. Very few FRBs have matches with sources observed at other wavelengths (Wikipedia - Fast Radio Burst).
...What we have come to appreciate is the seminal role played by clustered star formation in driving the physical and chemical evolution of the galaxies that host these stellar nurseries. Such concentrated sites of newborn stars along with their nebular environs constitute what are known as galactic ecosystems. These energized realms represent vital “crucibles” for growing the chemical complexity that is necessary for biotic processes.
If the Big Bang theory is correct, how fast is the universe expanding? Astronomers are facing a troubling disconnect between different methods used to measure the expansion rate, known as the Hubble constant. The two methods are giving similar but slightly different rates. Either one method is providing inaccurate results, or there is some kind of unknown physics operating in the universe.
