Related papers: A Possible Astronomically Aligned Monolith at Gard…
The temperature-magnetic-field phase diagram of the mixed honeycomb triangular lattice system K$_{2}$Mn$_{3}$(VO$_{4}$)$_{2}$CO$_{3}$ is investigated by means of magnetization, heat capacity and neutron scattering measurements. The results…
In this paper, we consider a little-studied observable in classical pure AdS3 gravity: the twist along a geodesic. The motivation is that the twist only supports on the geodesic so may be a candidate element in the center of the algebra in…
The Chinese Pyramids are huge ancient burial mounds. In the satellite images we can see some complexes where the main buildings are the pyramidal mounds of an emperor and his empress. Here we discuss a possible sunrise/sunset orientation of…
Canada is a triangle-shaped country, roughly speaking. We all know that the Atlantic Ocean is at its eastern corner in the Maritimes, and off the west coast of British Columbia is the Pacific Ocean. The Arctic Ocean, however, makes up the…
The long-term magnetic behavior of objects near the cooler end of the stellar main sequence is poorly understood. Most theoretical work on the generation of magnetism in these ultracool dwarfs (spectral type >=M7 stars and brown dwarfs)…
We use recently digitized sunspot drawings from Mount Wilson Observatory to investigate the latitudinal dependence of tilt angles of active regions and its change with solar cycle. The drawings cover the period from 1917 to present and…
Recent high resolution spectropolarimetric observations from Hinode detected the presence of supersonic downflows in a sunspot light bridge (Louis et al. 2009). These downflows occurred in localized patches, close to regions where the field…
Here we report on observations of the three-dimensional structure of a sunspot magnetic field from the photosphere to the chromosphere, obtained with the new visible/infrared spectro-polarimeter SPINOR. The observations, interpreted with a…
We present an optimal, linear-time algorithm for the following version of terrain guarding: given a 1.5D terrain and a horizontal line, place the minimum number of guards on the line to see all of the terrain. We prove that the cardinality…
Using adaptive optics on the W.M. Keck II telescope we imaged Titan several times during 1999 to 2001 in narrowband near-infrared filters selected to probe Titan's stratosphere and upper troposphere. We observed a bright feature around the…
We investigate features that are observed in Ca ii H sequences from Hinode in places where reversed granulation seems to interact with p-modes. These features appear ubiquitously in the quiet sun. They are co-spatial with reversed…
This paper discusses the solar orientation of the archaeological complex of Sigiriya, the Lion Rock, in Sri Lanka. We can see that the axis of this complex is oriented with the sunset of the zenithal sun.
The hypothesis of a companion object (Nemesis) orbiting the Sun was motivated by the claim of a terrestrial extinction periodicity, thought to be mediated by comet showers. The orbit of a distant companion to the Sun is expected to be…
Observational searches for asteroids orbiting near Earth's triangular Lagrange points face unique obstacles. A population of such asteroids would occupy a large projected area on the sky (possibly hundreds of square degrees) and is not…
We find that the mean meridional motion of the spot groups varies considerably on a time scale of about 5-20 years. The maximum amplitude of the variation is about 10-15 m/s in both the Sun's northern and the southern hemispheres. Variation…
The striking asymmetry of the ice cover during the Last Global Maximum suggests that the North Pole was in Greenland and then rapidly shifted to its present position in the Arctic See. A scenario which causes such a rapid geographic polar…
The polar magnetic field of the Sun is a manifestation of certain aspects of the dynamo process and is a good precursor for predicting a sunspot cycle before its onset. Although actual synoptic measurements of this field exist only from the…
Reports from the 2nd and 3rd Century AD attribute the first measurement of the angular size of the Sun to Thales of Miletus, in the 6th Century BC. Cleomedes, also in the 2nd Century AD, described a method to perform the measurement, based…
Digital images of the observations printed in the books "Rosa Ursina sive solis" and "Prodromus pro sole mobili" by Christoph Scheiner as well as the drawings from Scheiner's letters to Marcus Welser are analysed in order to obtain…
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…