We’re not supposed to look at the sun, but no one said anything about listening. If you, like amateur astronomer Thomas Ashcraft, had your radio tuned to the right frequency last Saturday evening, you would have heard the garbled effects of a solar flare drowning out radio waves here on Earth after it erupted on the surface of the sun. For those of you who still want to listen after the fact, you’re in luck:
Thomas Ashcraft is an independent, self-taught radio astronomer who operates his own Heliotown Observatory in north central New Mexico. Using optical telescopes and radio instruments, Ashcraft keeps an eye (and an ear) on the Sun, Jupiter, meteoric fireballs and transient luminous events called red sprites. He recorded the sound of the solar flare this weekend and shared his methodology and thoughts with DISCOVER writer Breanna Draxler via e-mail.
A tree’s rings mark both its age and the local environmental conditions, which allows researchers to track historical changes in an ecosystem. But tree rings can also encode signals from beyond Earth: Ancient trees in the Northern Hemisphere have preserved a radioactive souvenir from a 1200-year-old burst of cosmic rays.
Using tree rings, researchers have collected 3,000 years worth of data on the presence of the radioactive carbon isotope carbon-14 in the atmosphere. When examining the ebb and flow of carbon-14 over time, Japanese researchers noticed an increase during the 8th and 9th centuries CE. They decided to look at that period in detail by studying the yearly concentrations of carbon-14 in Japanese cedar trees. The cedars revealed a 1.2 percent carbon-14 spike that lasted less than a year between 774 and 775 CE, which corresponded with similar spikes in North American and European trees. This peak, twenty times the amount of variation normally caused by the sun’s fluctuations, resulted from a short-term burst of cosmic rays. But where did those rays come from—a supernova, a solar flare, or some other source?