Probing the sun
Neutrinos produced in the sun’s core could shed light on how much of the sun is composed of elements heavier than helium, Emily Conover reported in “Physicists spot a new class of neutrinos from the sun” (SN: 8/1/20, p. 11).
Reader Simon Read was curious about other ways physicists could study the sun. He suggested gravitational waves might be a good way to study the sun’s massive eddies.
In general, just about any accelerating massive object can produce the spacetime ripples known as gravitational waves, but most are too tiny to detect. That’s probably the case for gravitational waves from the churning of the sun, Conover says, “otherwise we would have seen them already.”
There’s more that goes into the formation and detection of gravitational waves than just an object’s mass. “For example, the object’s acceleration has to be large enough and the waves emitted have to match the frequency of gravitational waves that experiments can detect,” Conover says. Scientists typically detect gravitational waves from black holes that orbit around one another before colliding and merging into one. Solar eddies have much less mass, and the mass moves more slowly.
Additionally, to produce gravitational waves, the accelerating mass must be asymmetrical. “A perfectly spherical, spinning object would produce no gravitational waves no matter how fast you spin it and how massive it is,” Conover says. “In black hole collisions, you have big black holes circling each other, separated by empty space in between.” Swirling solar material wouldn’t be as asymmetric as the black hole scenario, so would likely produce smaller waves.
Black hole systems are relatively easy to understand theoretically: Black holes are all identical to one another aside from mass and spin. “That means it’s possible to calculate the gravitational waves you’d expect from a given pair, which is how physicists know what to look for,” Conover says. “That would be hard to do with the chaotic churning of the sun.”
Two extreme lightning bolts, called megaflashes, more than doubled previous records, Carolyn Gramling reported in “Two lightning megaflashes shattered distance and duration records” (SN: 8/1/20, p. 5).
Reader Lucille Cholerton wondered why megaflashes occur.
Megaflashes form within vast networks of thunderstorms and cloud cover called mesoscale convective systems. Within these systems can be broad swaths of steady rainfall called stratiform regions, Gramling says. Such regions have less lightning activity than other parts of mesoscale convective systems, which allows charges to build up in the clouds over very long distances. A spark, perhaps a flash of lightning from elsewhere, can trigger a cascade of electric discharges within a stratiform region, creating a megaflash.
Shoring up mussels
Biologists are on a mission to save a freshwater mussel from extinction, Stephen Ornes reported in “To save Appalachia’s endangered mussels, scientists hatched a bold plan” (SN: 8/1/20, p. 22).
“Getting readers to be concerned about survival [of] rhinos and tigers is simpler than the challenge that author Stephen Ornes sets and meets: making us care about these dinky invertebrates,” reader Guy Webster wrote. “He gives us scene-setting stories with human heroes, mixed with important information about the freshwater mussels,” Webster wrote. “Thanks for publishing stories like this.”