Related papers: Whither Does the Sun Rove?
A didactic sequence of activities on some topics of Astronomy, related mainly with the length and orientation of shadows cast by a gnomon, the movement of shadows during daytime in different seasons of the year, and finding the true…
Solar astrometry deals with the accurate measumerent of the solar diameter, and in general with the measurement of the shape of the Sun. During the last decades several techniques have been developed to monitor the radius and the irradiance…
The fields of occultation and microlensing are linked historically. Early this century, occultation of the Sun by the Moon allowed the apparent positions of background stars projected near the limb of the Sun to be measured and compared…
The Earth's revolution is modified by changes in inclination of its rotation axis. Despite the fact that the gravity field is central, the Earth's trajectory is not closed and the equinoxes drift. Milankovic (1920) argued that the shortest…
Earth's analemma is the lopsided figure eight marked out over a year by the position of the Sun in the sky observed at the same clock time each day. It shows how solar time deviates from clock time. The analemma's shape results from the…
With only five photographs of the Sun at different dates we show that the mass of Sun can be calculated by using a telescope, a camera, and the Kepler's third law. With these photographs we are able to calculate the distance between Sun and…
We describe the defining observations of the solar cycle that provide constraints for the dynamo processes operating within the Sun. Specifically, we report on the following topics: historical sunspot numbers and revisions; active region…
Using Greenwich sunspot data for 120 years it was recently observed that activity regions on the Sun's surface tend to lie along smoothly changing longitude strips 180 degrees apart from each other. However, numerical experiments with…
The pyramids of ancient Egypt are said to have shone brilliantly in the sun. Surfaces of polished limestone would not only have reflected diffusely in all directions, but would also likely have produced specular reflections in particular…
We propose a LSST Solar System near-Sun Survey, to be implemented during twilight hours, that extends the seasonal reach of LSST to its maximum as fresh sky is uncovered at about 50 square degrees per night (1500 sq. deg. per lunation) in…
The introduction of coordinates representing the points of view of various observers results in the possibility of horizons when acceleration and gravitation are included. A horizon is a surface of possible light beams in a region of space…
The determination of the birth radius of the Sun is important to understand the evolution and consequent disruption of the Sun's birth cluster in the Galaxy. Motivated by this fact, we study the motion of the Sun in the Milky Way during the…
Helioseismology has allowed us to infer the rotation in the greater part of the solar interior with high precision and resolution. The results show interesting conflicts with earlier theoretical expectations, indicating that the the Sun is…
Regardless of the physical origin of stellar magnetic fields - fossil or dynamo induced - an inclination angle between the magnetic and rotation axes is very often observed. Absence of observational evidence in this direction in the solar…
The nature of coronal wave fronts is deeply debated. They are observed in several wavelength bandpasses in spectra, and are frequently interpreted as magnetosonic waves propagating in the lower solar atmosphere. However, they can be…
Improving irradiance forecasting is critical to further increase the share of solar in the energy mix. On a short time scale, fish-eye cameras on the ground are used to capture cloud displacements causing the local variability of the…
The Sun continuously expels a fraction of its own mass in the form of a steadily accelerating outflow of ionized gas called the "solar wind." The solar wind is the extension of the Sun's hot (million-degree Kelvin) outer atmosphere that is…
Solar eclipses, as rare astronomical events, often evoke a profound sense of wonder and awe within the human spirit. However, for ordinary people, the extremely short preparation time, a few hours of notice from friends or social media, and…
Although the Sun is our closest star by many orders of magnitude and despite having sunspot records stretching back to ancient China, our knowledge of the Sun's magnetic field is far from complete. Indeed, even now, after decades of study,…
Standard solar models predict a solar luminosity that gradually increased by about 30% over the past 4.5 billion years. Under the faint sun, Earth should have been frozen solid for most of its existence. Yet, running water is observed to…