Accelerated expansion refers to the phenomenon where the rate of expansion of the universe is increasing over time, rather than slowing down as expected. This was first discovered in the late 1990s through observations of distant supernovae.
Dark energy is currently the leading explanation for accelerated expansion. It is a hypothetical form of energy that is thought to permeate the entire universe and is believed to be responsible for the expansion of the universe accelerating over time.
Lightcurves, which are graphs of the brightness of an object over time, are crucial in studying accelerated expansion. By observing the lightcurves of distant supernovae, scientists can determine the distance to these objects and how their brightness changes over time. This information can then be used to understand the expansion rate of the universe.
Scientists use a technique called the cosmic distance ladder to measure the expansion rate of the universe. This involves using the brightness of objects at known distances, such as Cepheid variable stars and Type Ia supernovae, to calibrate the distance to more distant objects with similar lightcurves. By measuring the distance to these objects, scientists can then calculate the expansion rate of the universe.
In addition to lightcurves, scientists also use other methods to study accelerated expansion, including galaxy surveys, gravitational lensing, and the cosmic microwave background. These methods provide complementary information and help to further understand the nature of dark energy and its role in the accelerating expansion of the universe.