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 5An 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 7Portrait 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 10ALMA is the world's most powerful telescope for studying the Universe at submillimeter and millimeter wavelengths. (from Observational astronomy)
Image 17Artist 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 18Amateur astronomer recording observations of the sun. (from Amateur astronomy)
Image 28Places like
Paranal Observatory offer crystal clear skies for observing astronomical objects with or without instruments. (from Amateur astronomy)
Image 32Comparison of
CMB (Cosmic microwave background) results from satellites
COBE,
WMAP and Planck documenting a progress in 1989–2013 (from History of astronomy)
Image 36Segment of the
astronomical ceiling of Senenmut's Tomb (circa 1479–1458 BCE), 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)
This is a
Featured article, which represents some of the best content on English Wikipedia.
The definition of the term planet has changed several times since the word was coined by the
ancient Greeks.
Greek astronomers employed the term ἀστέρες πλανῆται (asteres planetai), 'wandering stars', for star-like objects which apparently moved over the sky. Over the millennia, the term has included a variety of different
celestial bodies, from the
Sun and the
Moon to
satellites and
asteroids.
In modern astronomy, there are two primary conceptions of a planet. A planet can be an astronomical body that dynamically dominates its region (that is, whether it controls the fate of other smaller bodies in its vicinity) or it is defined to be in hydrostatic equilibrium (it has become gravitationally rounded and compacted). These may be characterized as
the dynamical dominance definition and
the geophysical definition. (Full article...)
... that Jessen's icosahedron has been used for both the "Skwish" children's toy and a NASA proposal for a "super ball bot" to cushion space landers on other planets?
Coronal loops are huge loops of
magnetic field beginning and ending on the
Sun's visible surface (
photosphere) projecting into the solar atmosphere (
corona). Image of typical coronal loops observed by
TRACE.