Flare Stars

Flare stars are usually very cool, dim dwarf stars with much smaller sizes and masses than our Sun. The flares are not predictable either in time or intensity. Like solar flares but generally much larger, stellar flares are caused when strong magnetic field loops are broken by turbulence in the atmosphere of the star, causing radiation and hot ionized gas to erupt into space.

Proxima Centauri

Proxima Centauri is the nearest star to our Sun and it also happens to be a flare star. A red dwarf star that is typically invisible to the naked eye, Proxima Centauri randomly undergoes huge increases in brightness that last for a few hours.

Below is an observed light curve for Proxima Centauri. The video covers two days of Hubble Space Telescope observations, and each plotted time interval corresponds to only 4 minutes of real time. Two large flares can be clearly heard during the video. Also interesting to note are the regular silent gaps in observations. These occur because the Hubble Space Telescope has an orbit time of about 95 mins, which means observations of Proxima Centauri were blocked by the Earth every hour or so. The video scans over time (x-axis) and modulates pitch based on magnitude (y-axis). Lower pitch represents dimmer magnitudes.

The next video is an observed spectrum for Proxima Centauri. This video scans across a plot of brightness measured in flux or intensity of light (y axis) versus wavelength (x axis), moving from blue to red wavelengths from 3800 to 7200 angstroms. Lower pitch represents weaker flux. Because Proxima Centauri is a dim red dwarf star, its spectrum peaks at larger wavelengths, so you will hear a gradual increase in flux during the video.

These spectral data were obtained with the Hubble Space Telescope, provided courtesy of Jim Davenport et al. 2016 (link). Optical light curve is from the Microvariability and Oscillations of Stars (MOST) satellite (Walker et al. 2003 (link)).