Stellar astrophysics
Stars and Planets
Stellar astrophysics
With the aim of understanding nothing less than the universe, astrophysics applies physical laws to the processes in space. This approach has proven to be extremely successful and, as a result, modern astrophysics covers all scales, from stars and their planetary systems to the cosmic network consisting of dark matter and the clusters of galaxies embedded in it.
Observations are indispensable for all astrophysical studies. Astrophysicists cannot enter their laboratories, nor can they set up experiments. Answering questions in astrophysics therefore means building telescopes and suitable instruments, carrying out well-planned observations and interpreting the data using suitable theoretical models.
Stellar activity
Flares and coronal mass ejections (CMEs) are well studied on the Sun. However, both phenomena can also be detected on stars. Stellar flares have been known since the 1920s. The term "flare star" was born when enormous increases in brightness were detected in the dwarf star UV Ceti of spectral type M. From this point onwards, flares were detected on a large number of stars from the X-ray to the radio range. In contrast, stellar mass ejections have only been detected on very few stars. This does not a priori mean that they occur much more rarely, but the type of detection is more difficult than for flares. Flares can be detected using light curves created from photometric time series. In these light curves, flares show a characteristically rapid rise and a slower fall.
Gravitational lensing effects
The deflection of light rays by heavy masses is known as the gravitational lens effect. The effect was first correctly described by Albert Einstein with his general theory of relativity. In many cases, gravitational lensing effects can be described by analogy to the diffraction of light in optical lens systems. Many useful applications in cosmology have been discovered through this property of matter and light.