Astronomy Picture of the Day Index - Space Technology: Earth Observatories

APOD: 2005 February 7 - A Telescope Laser Creates an Artificial Star
Explanation: What do you get when you combine one of the world's most powerful telescopes with a powerful laser? An artificial star. Monitoring fluctuations in brightness of a genuine bright star can indicate how the Earth's atmosphere is changing, but many times no bright star exists in the direction where atmospheric information is needed. Therefore, astronomers have developed the ability to create an artificial star where they need it -- with a laser. Subsequent observations of the artificial laser guide star can reveal information so detailed about the blurring effects of the Earth's atmosphere that much of this blurring can be removed by rapidly flexing the mirror. Such adaptive optic techniques allow high-resolution ground-based observations of real stars, planets, nebulae, and the early universe. Above, a laser beam shoots out of the Keck II 10-meter telescope on Mauna Kea in Hawaii in 2002, creating an artificial star.

APOD: 2006 May 14 - The Very Large Array of Radio Telescopes
Explanation: The most photogenic array of radio telescopes in the world has also been one of the most productive. Each of the 27 radio telescopes in the Very Large Array (VLA) is the size of a house and can be moved on train tracks. The above pictured VLA, inaugurated in 1980 is situated in New Mexico, USA. The VLA has been used to discover water on planet Mercury, radio-bright coronae around ordinary stars, micro-quasars in our Galaxy, gravitationally-induced Einstein rings around distant galaxies, and radio counterparts to cosmologically distant gamma-ray bursts. The vast size of the VLA has allowed astronomers to study the details of super-fast cosmic jets, and even map the center of our Galaxy. An upgrade of the VLA is being planned.

APOD: 1999 February 1 - The Subaru Telescope
Explanation: Last week, Japan's new Subaru Telescope made its first observations of the sky. The gray building housing Subaru is visible just left of the white Keck domes near the photo's center. Subaru is the latest in the class of optical telescopes using a mirror with a diameter greater than 8 meters. Subaru's 8.3-meter primary is the largest single-piece optical telescope mirror yet made, and is so thin that its precise shape can be monitored and adjusted. Subaru will be owned and operated by Japan but located at the top of Hawaii's Mauna Kea, a dormant volcano famous for housing several of the world's leading telescopes.