Herschel Prisms

Solar observation in white light (the Solar photosphere ñ Sun spots, Solar granulation and Solar faculae) is one of the most interesting activities in astronomy.

Herschel Prisms - Sun Spots Limb darkening of the Sun is a constant Solar phenomenon and immediately visible when aiming the telescope at the Sun. Limb darkening is caused by the fact that the Sun consists of hot gas whose temperature is reducing to- wards the surface. Looking at the middle of the Sun means to look onto the hottest and deepest region. Looking at the edge however shows less dense and consequently less bright regions. Were the Sun a solid body, no limb darkening could be observed.

Herschel Prisms Sunspot Close up Sun spots consist of a core region (Umbra) and a brighter surrounding region (Penumbra). Sun spots are cooler (approx. 8000°C) than the undisturbed Solar face. At this locations magnetic storms are bursting through the granu- lated photosphere.

All Sun spots go through a detailed cycle ñ normally from a small single spot evolving into a complex group of spots developing distinct magnetic north and south poles. Changes in these complex groups are the fastest moving changes observable in the Solar system. Complex changes may take just minutes, making the Solar observation in white light so very interesting.

Photospheric faculae. Faculae are being recognised as bright areas within the Solar surface and usually are grouped around Sun spots. These faculae regions are hotter than the rest of the Solar photosphere. During observation in integral light with a Herschel-Prism such bright regions are mainly visible near the limb of the Sun, since the area appears darker than the central regions.