Night sky or good binoculars, the planets appear as discs demonstrating finite size, and it is possible to observe orbiting moons which cast shadows onto the host planet's surface. Venus is the most prominent planet, often called the "morning star" or "evening star" because it is brighter than the stars and often the only "star" visible near sunrise or sunset, depending on its location in its orbit. Mercury, Mars, Jupiter and Saturn are also visible to the naked eye. Earth's Moon is a grey disc in the sky with cratering visible to the naked eye. It spans, depending on its exact location,
Solar power in Spain The Andasol 1 power plant went online in November 2008, and has a thermal storage system which absorbs part of the heat produced in the solar field during the day. This heat is then stored in a molten salt mixture and used to generate electricity during the night, or when the sky is overcast. A 15 MWe solar-only power tower plant, the Solar Tres project, is in the hands of the Spanish company SENER, employing molten salt technologies for receiving and energy storage. Its 16-hour molten salt storage system will be able to deliver power around the clock. The Solar