This paper is the first one of a series of two on the role of the optical dispersion in the historical development of early quantum mechanics. As preparation for the successive paper on Ladenburg’s development of the phenomenological theory of radiative transitions between the stationary states of an atom by Einstein, we present here the current

We present a detailed study of the neutral and ionized gas phases in the galactic wind for the nearby starburst galaxy NGC 5394 based on new integral field spectroscopy obtained with the INTEGRAL fibre system at the William Herschel Telescope. The neutral gas phase in the wind is detected via the interstellar Na I D doublet absorption. After a

Context. Solar prominences are subject to both field-aligned (longitudinal) and transverse oscillatory motions, as evidenced by an increasing number of observations. Large-amplitude longitudinal motions provide valuable information on the geometry of the filament-channel magnetic structure that supports the cool prominence plasma against gravity

Utilizing the unique location of red clump giants on colour-magnitude diagrams obtained from various near-infrared surveys, we derived specific reddening-distance relations towards 119 Galactic novae for which independent reddening measurements are available. Using the derived distance-extinction relation and the independent measurements of

We report the discovery of an optical Einstein ring in the Sculptor constellation, IAC J010127-334319, in the vicinity of the Sculptor dwarf spheroidal galaxy. It is an almost complete ring (˜300°) with a diameter of ˜4.5 arcsec. The discovery was made serendipitously from inspecting Dark Energy Camera (DECam) archive imaging data. Confirmation of

We present the study of the colour-magnitude diagram of the cluster Abell 2151 (A 2151), with a particular focus on the low-mass end. The deep spectroscopy with AF2/WYFFOS@WHT and the caustic method enable us to obtain 360 members within 1.3 R200 and absolute magnitude M_r ≲ M_r^{ast }+6. This nearby cluster shows a well defined red sequence up to