Related papers: Solar Oblateness from Archimedes to Dicke
From 1997 the Observatorio Nacional has been observing the Sun with an astrolabe in order to study variations on the solar semi-diameter. Till now more than 20.000 observations were done. The observations taken in the year of 2001 were…
The Sun is the main energy source to Earth, and understanding its variability is of direct relevance to climate studies. Measurements of total solar irradiance exist since 1978, but this is too short compared to climate-relevant time…
Exactly 500 years ago, Nicolaus Copernicus drew a lattice of lines on a panel above the doorway to his rooms at Olsztyn Castle, then in the Bishopric of Warmia. Although its design has long been regarded as some kind of reflecting vertical…
We propose an algorithm that can be used by amateur astronomers to analyze the images acquired during solar eclipses. The proposed algorithm analyzes the image, detects the eclipse and produces results for parameters like magnitude of…
DI Herculis is an eclipsing binary famous for a longstanding disagreement between theory and observation of the apsidal precession rate, which was resolved when both stars were found to be severely misaligned with the orbit. We used data…
Using wavelet analysis approach, we can derive a measure of the disorder content of solar activity, following the temporal evolution of the so-called wavelet entropy. The interesting feature of this parameter is its ability to extract a…
In helioseismology, there is a well-known offset between observed and computed oscillation frequencies. This offset is known to arise from improper modeling of the near-surface layers of the Sun, and a similar effect must occur for models…
We present evidence of hitherto undiscovered global-scale oscillations in the near-surface shear layer of the Sun. These oscillations are seen as large scale variations of radial shear in both the zonal and meridional flows relative to…
Longitude determination at sea gained increasing commercial importance in the late Middle Ages, spawned by a commensurate increase in long-distance merchant shipping activity. Prior to the successful development of an accurate marine…
We report development of a simple and affordable radio interferometer suitable as an educational laboratory experiment. With the increasing importance of interferometry in astronomy, the lack of educational interferometers is an obstacle to…
We express the position of the Sun in the sky as a function of time and the observer's geographic coordinates. Our method is based on applying rotation matrices to vectors describing points on the celestial sphere. We also derive direct…
Analysis of f-mode frequencies has provided a measure of the radius of the Sun which is lower, by a few hundredths per cent, than the photospheric radius determined by direct optical measurement. Part of this difference can be understood by…
A moderately massive early Sun has been proposed to resolve the so-called faint early Sun paradox. We calculate the time-evolution of the solar mass that would be required by this hypothesis, using a simple parametrized energy-balance model…
Changes in planetary obliquity, or axial tilt, influence the climates on Earth-like planets. In the solar system, the Earth's obliquity is stabilized due to interactions with our moon and the resulting {small amplitude variations…
The astronomer E.V. Pitjeva, by analyzing with the EPM2008 ephemerides a large number of planetary observations including also two years (2004-2006) of normal points from the Cassini spacecraft, phenomenologically estimated a statistically…
The ultra-precise photometric space satellite MOST (Microvariability and Oscillations of STars) will provide the first opportunity to measure the albedos and scattered light curves from known short-period extrasolar planets. Due to the…
The growing interest in the "Medieval Climate Anomaly" (MCA) and its possible link to anomalous solar activity has prompted new reconstructions of solar activity based on cosmogenic radionuclides. These proxies however do not sufficiently…
The variable Sun is the most likely candidate for natural forcing of past climate change on time scales of 50 to 1000 years. Evidence for this understanding is that the terrestrial climate correlates positively with solar activity. During…
The history of astrometry, the branch of astronomy dealing with the positions of celestial objects, is a lengthy and complex chronicle, having its origins in the earliest records of astronomical observations more than two thousand years…
In a classic 1982 paper in this journal, Jean Meeus used a statistical approach for finding the mean frequency of a total and an annular eclipse of the Sun at a given place on the surface of the Earth. In this current paper we tackle the…