Light curve of the week: RR Lyrae
The above light curve, with its periodic increase and decrease in brightness, has the clear signature of an RR Lyrae stars. The pulsations, caused by increases and decreases in the radii and temperatures of these types of stars, typically vary on times-scales ranging from a few hours to and a couple of days. These stars are also evolved stars, meaning that they tend to be older than the Sun with typical ages of around 10 billion years.
RR Lyraes are not only nice to look at, they are also very important for the field of astronomy, as they allow us calibrate the ‘distance ladder’ and thus help us determine the distance to far away objects. They can do that because the time between the pulsations depends on the mass, temperature and intrinsic brightness (the brightness if you were right next to the star) of the star. When we compare the intrinsic brightness to the brightness that we see from Earth, we can calculate how far away the RR Lyrae star is using the inverse-square law.
This target was discussed on the PHT discussion forums at: https://www.zooniverse.org/projects/nora-dot-eisner/planet-hunters-tess/talk/2107/1550146