- The Avenues (Wikivoyage)
Lush Golden Gate Park, foggy Sunset, hilly Richmond, and the steep cliffs of Lands End make up The Avenues of western San Francisco. A mostly residential area, this is where you will find one of the most ethnically-diverse populations of the city, San Francisco’s main beach, charming shops and restaurants, spectacular coastline scenery, and the massive Golden Gate Park with its many gardens, lakes, pastures, and forests. The area is bounded by the Pacific Ocean on the west, Lake Street on the north, Arguello Blvd and Stanyan Street (from Lake to Frederick Street) and 7th Avenue (from Lincoln to around Golden Gate Heights Park, or about Quintara) and 19th Avenue (from Quintara to Sloat) on the east, and Sloat Blvd on the south.
- Binary star (Wikipedia)
A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in which case they are called visual binaries. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as spectroscopy (spectroscopic binaries) or astrometry (astrometric binaries). If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other; these pairs are called eclipsing binaries, or, together with other binaries that change brightness as they orbit, photometric binaries.