A lot of these stars pulsate due to the way their upper layers absorb and emit energy from the core below, and while that’s complex it’s fairly well understood. However, a lot of these stars have a second periodicity on top of the primary one that generally lasts for months to years — much much longer than the primary pulsation period. These are called long secondary periods, and were first seen in red giants back in the 1930s. However, despite a century of observations the cause hasn’t been clear.
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.