How big is the sun?5 answersThe size of the Sun, specifically its radius, has been a subject of historical and modern scientific inquiry. Early estimations by Greek astronomers and subsequent measurements in the 17th and 19th centuries varied, with values around 1800" and 1920", respectively. However, with advancements in technology and the use of high-precision instruments like the Michelson Doppler Imager (MDI) and the Helioseismic and Magnetic Imager (HMI), a more accurate value of the solar radius has been determined. The International Astronomical Union revised the standard solar radius in 2015 based on modern measurements, showing a temporal variability in the "seismic radius" linked to solar activity. Currently, the Sun's radius is estimated to be around 696,000 km, with no significant secular variation observed over the past three centuries.
What temperatures does solar ovens reach?4 answersSolar ovens can reach temperatures ranging from 80°C to 328°C. The specific temperature achieved depends on various factors such as the design of the oven, the type of solar collector used, and the weather conditions. For example, a solar thermal powered bakery oven model was able to achieve a temperature of 168°C inside the oven cavity when the coils surface was maintained at an average temperature of 300°C. Another study reported a maximum temperature of 150°C in a solar oven heated by a Scheffler concentrator. It is worth noting that these temperatures are sufficient for cooking and baking purposes, making solar ovens a viable option for energy-efficient cooking.
How big is the sun?5 answersThe size of the Sun is approximately 696,000 km in radius. The measurement of the Sun's diameter has been a topic of study for centuries, with early estimations by Greek astronomers being around 1800". However, more recent measurements using high sensitivity instruments on satellites have provided a revised value for the solar radius, known as the "seismic radius". These measurements show a temporal variability in anti-phase with solar activity and have led to a revision of the standard solar radius by the International Astronomical Union in 2015. Despite variations in measurements over the past three centuries, a homogenized database does not reveal any significant secular variation in the solar diameter, with a result for the semi-diameter at 1 AU of 960".
How does solar wind cause space weather?5 answersSolar wind causes space weather through various physical mechanisms. The solar wind, which is the continuous outflow of the hot solar atmosphere into space, interacts with the Earth's magnetosphere and upper atmosphere, leading to several effects. These effects include the compression and reconnection of Earth's magnetic field, heating of the upper atmosphere, and the generation of solar radio emissions. The solar wind carries the Sun's magnetic field, creating a cavity in the interstellar medium dominated by the solar magnetic field. The interaction between the solar wind and Earth's magnetosphere can result in geomagnetic storms, auroras, and the formation of radiation belts. The solar wind also influences the dynamics of small-scale structures and turbulence in near-Earth space, which can affect space weather predictions. Overall, the varying solar wind, including its speed, magnetic field orientation, and pressure, plays a crucial role in the processes that cause space weather phenomena.
What metalcities do the stars of the solar system have?4 answersThe metallicity of stars in the solar system varies. Elemental abundance determinations from the solar photosphere have shown a homogeneous distribution of metals in stars, challenging the assumption of chemical homogeneity in the solar neighborhood. However, a large-scale project analyzing spectra of solar-type stars in the solar neighborhood has provided initial metallicity estimates for 4043 stars, which will contribute to understanding chemical homogeneity in the solar neighborhood. Additionally, high-resolution chemical abundance results of metal-poor dwarf stars in the solar neighborhood have shown metallicities ranging from -1.6 to -2.8, with a mean value of [Fe/H] = -2.28. Furthermore, a study of KM-type giant stars with metallicity close to solar has shown that the Rb deficiency found in M dwarfs is smaller in giant stars, with NLTE [Rb/Fe] ratios close to solar in the full metallicity range.
Does evaporation increase with height?5 answersEvaporation rate can increase with height in certain cases. For example, in the study by Leu et al., it was found that the electrohydrodynamic (EHD) effect on the evaporation rate increased with increases in electrode pitch and decreases in electrode height. Additionally, in the study by Zhang et al., it was observed that the circulation flow rate and thermal performance of a two-phase thermosyphon loop initially increased and then remained constant with the increase of the height difference between the condenser and the evaporator. However, it is important to note that the relationship between evaporation and height can be influenced by various factors such as applied voltage, air flow velocity, and liquid head. Therefore, it is necessary to consider these factors when studying the effect of height on evaporation.