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download for last week:2NGC 2419 Intergalactic Wanderer
download for last week:3Galaxy NGC 7714 After Collision
download for last week:2Colorful Clouds Near Rho Ophiuchi
download for last week:1Stripping ESO 137-001
download for last week:3The Shark Nebula
download for last week:3Announcing Comet Catalina
download for last week:6A Sagittarius Triplet
download for last week:1NGC 4372 and the Dark Doodad
download for last week:1Stardust in Perseus
download for last week:1M51 The Whirlpool Galaxy
download for last week:0LDN 988 and Friends
download for last week:10M45 The Pleiades Star Cluster
download for last week:2Ghosts and Star Trails
download for last week:4Ultraviolet Rings of M31
download for last week:0Puppis A Supernova Remnant
A star is a luminous sphere of plasma held together by its own gravity. The nearest star to Earth is the Sun. Other stars, mostly in the Milky Way, are visible from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, and the brightest stars gained proper names. Extensive catalogues of stars have been assembled by astronomers, which provide standardized star designations. For at least a portion of its life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space. Once the hydrogen in the core of a star is nearly exhausted, almost all naturally occurring elements heavier than helium are created by stellar nucleosynthesis during the star's lifetime and, for some stars, by supernova nucleosynthesis when it explod...
Fun is the enjoyment of pleasure, particularly in leisure activities. Fun is an experience — short-term, often unexpected, informal, not cerebral and generally purposeless. It is an enjoyable distraction, diverting the mind and body from any serious task or contributing an extra dimension to it. Although particularly associated with recreation and play, fun may be encountered during work, social functions, and even seemingly mundane activities of daily living. It may often have little to no logical basis, and opinions on whether or not an activity is fun may differ. A distinction between enjoyment and fun is difficult but possible to articulate,fun being a more spontaneous, playful, or active event. There are psychological and physiological implications to the experience of fun.
A galaxy is a gravitationally bound system consisting of stars, stellar remnants, interstellar gas and dust, and dark matter. The word galaxy is derived from the Greek galaxias (γαλαξίας), literally "milky", a reference to the Milky Way. Examples of galaxies range from dwarfs with just a few thousand (103) stars to giants with one hundred trillion (1014) stars, each orbiting their galaxy's own center of mass. Galaxies have historically been categorized according to their visual morphology, including elliptical, spiral, irregular, and starburst. Many galaxies are believed to have black holes at their active center. The Milky Way's central black hole, known as Sagittarius A*, has a mass four million times that of our Sun. The observable universe contains hundreds of billions (more than 1011) of galaxies. Most are 1,000 to 100,000 parsecs in diameter and usually separated by distances on the order of millions of parsecs (or megaparsecs). The space between galaxies is filled with...
Space is the boundless three-dimensional extent in which objects and events have relative position and direction. Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum known as spacetime. In mathematics, "spaces" are examined with different numbers of dimensions and with different underlying structures. The concept of space is considered to be of fundamental importance to an understanding of the physical universe. However, disagreement continues between philosophers over whether it is itself an entity, a relationship between entities, or part of a conceptual framework. Debates concerning the nature, essence and the mode of existence of space date back to antiquity; namely, to treatises like the Timaeus of Plato, or Socrates in his reflections on what the Greeks called khora (i.e. "space"), or in the Physics of Aristotle (Book IV, Delta) in the definition of ...