Professional astronomy is split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects. This data is then analyzed using basic principles of physics. Theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. These two fields complement each other. Theoretical astronomy seeks to explain observational results and observations are used to confirm theoretical results.
Astronomy is one of the few sciences in which amateurs play an active role. This is especially true for the discovery and observation of transient events. Amateur astronomers have helped with many important discoveries, such as finding new comets. (Full article...)
Image 2Comparison of CMB (Cosmic microwave background) results from satellites COBE, WMAP and Planck documenting a progress in 1989–2013 (from History of astronomy)
Image 4Artist conception of the Big Bang cosmological model, the most widely accepted out of all in physical cosmology (neither time nor size to scale) (from Physical cosmology)
Image 14The main platform at La Silla hosts a huge range of telescopes with which astronomers can explore the Universe. (from Observational astronomy)
Image 15ALMA is the world's most powerful telescope for studying the Universe at submillimeter and millimeter wavelengths. (from Observational astronomy)
Image 16Amateur astronomer recording observations of the sun. (from Amateur astronomy)
Image 18Segment of the astronomical ceiling of Senenmut's Tomb (circa 1479–1458 BC), depicting constellations, protective deities, and twenty-four segmented wheels for the hours of the day and the months of the year (from History of astronomy)
Image 19An example of a gravitational lens found in the DESI Legacy Surveys data. There are four sets of lensed images in DESI-090.9854-35.9683, corresponding to four distinct background galaxies—from the outermost giant red arc to the innermost bright blue arc, arranged in four concentric circles. All of them are gravitationally warped—or lensed—by the orange galaxy at the very center. Dark matter is expected to produce gravitational lensing also. (from Physical cosmology)
Image 23Portrait of the Flemish astronomer Ferdinand Verbiest who became head of the Mathematical Board and director of the Observatory of the Chinese emperor in 1669 (from Astronomer)
Image 28An image of the Cat's Paw Nebula created combining the work of professional and amateur astronomers. The image is the combination of the 2.2-metre MPG/ESO telescope of the La Silla Observatory in Chile and a 0.4-meter amateur telescope. (from Amateur astronomy)
Image 33Places like Paranal Observatory offer crystal clear skies for observing astronomical objects with or without instruments. (from Amateur astronomy)
Image 34The inflationary theory as an augmentation to the Big Bang theory was first proposed by Alan Guth of MIT. Inflation solves the 'horizon problem' by making the early universe much more compact than was assumed in the standard model. Given such smaller size, causal contact (i.e., thermal communication) would have been possible among all regions of the early universe. The image was an adaptation from various generic charts depicting the growth of the size of the observable universe, for both the standard model and inflationary model respectively, of the Big Bang theory. (from Physical cosmology)
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Grayscale image of Umbriel from Voyager 2, January 1986. Umbriel's surface is heavily battered; the bright crater Wunda can be seen at the top of the image.
Umbriel (/ˈʌmbriəl/) is the third-largest moon of Uranus. It was discovered on October 24, 1851, by William Lassell at the same time as neighboring moon Ariel. It was named after a character in Alexander Pope's 1712 poem The Rape of the Lock. Umbriel consists mainly of ice with a substantial fraction of rock, and may be differentiated into a rocky core and an icy mantle. The surface is the darkest among Uranian moons, and appears to have been shaped primarily by impacts, but the presence of canyons suggests early internal processes, and the moon may have undergone an early endogenically driven resurfacing event that obliterated its older surface.
Covered by numerous impact craters reaching 210 km (130 mi) in diameter, Umbriel is the second-most heavily cratered satellite of Uranus after Oberon. The most prominent surface feature is a ring of bright material on the floor of Wunda crater. This moon, like all regular moons of Uranus, probably formed from an accretion disk that surrounded the planet just after its formation. Umbriel has been studied up close only once, by the spacecraft Voyager 2 in January 1986. It took several images of Umbriel, which allowed mapping of about 40% of the moon's surface. (Full article...)
The International Space Station is photographed by an STS-134 crew member on the space shuttle Endeavour after the station and shuttle began their post-undocking relative separation. Undocking of the two spacecraft occurred on May 29, 2011.
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