Related papers: Whither Does the Sun Rove?
The figure of the Sun reflects its inner structure and dynamics, influencing also the perihelion precession of close orbiting bodies, like Mercury. To study the solar figure from ground, the deformation on the solar image induced by the…
Fast (>700 km/s) and slow (~400 km/s) winds stream from the Sun, permeate the heliosphere and influence the near-Earth environment. While the fast wind is known to emanate primarily from polar coronal holes, the source of the slow wind…
Kipping (2017) discusses relativistic reflection from light sails. As an extension to this work, we present a new formula for relativistic reflection of sunlight from a light sail moving at a velocity inclined at an arbitrary angle, using…
The Sun was fainter when the Earth was young, but the climate was generally at least as warm as today; this is known as the `faint young Sun paradox'. Rosing et al. [1] claim that the paradox can be resolved by making the early Earth's…
In 1777 Ru{\dj}er Bo\v{s}kovi\'c observed sunspots, determined their positions and the solar rotation elements by his own methods briefly described here. We repeat his calculations of the mean solar time, sunspot positions, and solar…
Observations of the Earth as a planet using the earthshine technique (i.e. looking at the light reflected from the darkside of the Moon), have been used for climate and astrobiology studies. They provide information about the planetary…
Periodic changes in a stellar magnetic field can be explained in two ways: the oblique rotator model or the solar cycle model. Although many papers favor the oblique rotator model, there has not been enough evidence to rule out the solar…
The use of the observed positions of celestial bodies to determine the location of a navigator and to direct vessels, was an aspiration of ancient seafarers. Various peoples, in the Mediterranean as much as in the Indian Ocean, in China as…
Detailed models of the solar cycle require information about the starting time and rise time as well as the shape and amplitude of the cycle. However, none of these models includes a discussion of the variations in the length of the cycle,…
Observations of the Sun in the visible spectral range belong to standard measurements obtained by instruments both on the ground and in the space. Nowadays, both nearly continuous full-disc observations with medium resolution and dedicated…
Observations of the Sun and of Sun-like stars provide access to different aspects of stellar magnetic activity that, when combined, help us piece together a more comprehensive picture than can be achieved from only the solar or the stellar…
Sunspots are concentrations of magnetic field visible on the solar surface (photosphere). It was considered implausible that solar flares, as resulted from magnetic reconnection in the tenuous corona, would cause a direct perturbation of…
This article surveys the development of observational understanding of the interior rotation of the Sun and its temporal variation over approximately forty years, starting with the 1960s attempts to determine the solar core rotation from…
A new method for determining the stellar rotation period is proposed here, based on the detection of starspots during transits of an extra-solar planet orbiting its host star. As the planet eclipses the star, it may pass in front of a…
The Sun provides a standard reference against which we compare the chemical abundances found anywhere else in the Universe. Nevertheless, there is not a unique 'solar' composition, since the chemical abundances found in the solar interior,…
We investigate the effects of atmospheric dispersion on observations of the Sun at the ever-higher spatial resolutions afforded by increased apertures and improved techniques. The problems induced by atmospheric refraction are particularly…
Minor bodies of the solar system can be used to measure the spectrum of the Sun as a star by observing sunlight reflected by their surfaces. To perform an accurate measurement of the radial velocity of the Sun as a star by this method, it…
The sunspots and other solar activity indicators tend to cluster on the surface of the Sun.These clusters very often occur at certain longitudes that persist in time.It is of general interest to find new and simple ways to characterize the…
Different analyses of identical Hinode SOT/SP data of quiet-sun magnetic fields have in the past led to contradictory answers to the question of whether the angular distribution of field vectors is preferentially horizontal or vertical.…
Orbit determination of spacecraft in orbit has been mostly dependent on either GNSS satellite signals or ground station telemetry. Both methods present their limitations, however: GNSS signals can only be used effectively in earth orbit,…