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Definition of planet
The definition of "planet" has for some time been the subject of intense debate. Although the word dates back thousands of years, no officially decreed scientific definition of "planet" existed before the early 21st century. Until the beginning of the 1990s, there was little need for one, as astronomers had only a single sample of planets in solar system to study, and one small enough for its many irregularities to be dealt with individually.
However, after 1992 and the discovery of the myriad tiny worlds beyond the orbit of Neptune, the size of the sample rose from nine to at least several dozen. Following the discovery of the first extrasolar planet beyond our solar system in 1992, the number of samples has now reached hundreds. These revelations not only increased the number of potential planets, but, in their variety and peculiarity (some nearly large enough to be stars, others smaller than our Moon) challenged long perceived notions of what a planet could be.
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Space & Time News
December 24, 2025
Dec. 22, 2025 Astronomers have uncovered a massive hidden planet and a rare “failed star” by combining ultra-precise space data with some of the sharpest ground-based images ever taken. Using the Subaru Telescope in Hawaiʻi, the OASIS survey tracked subtle ...
Dec. 19, 2025 Gravitational waves from black holes may soon reveal where dark matter is hiding. A new model shows how dark matter surrounding massive black holes leaves detectable fingerprints in the waves recorded by future space ...
Dec. 17, 2025 Researchers have shown that quantum signals can be sent from Earth up to satellites, not just down from space as previously believed. This breakthrough could make global quantum networks far more powerful, affordable, and ...
Dec. 6, 2025 SQUIRE aims to detect exotic spin-dependent interactions using quantum sensors deployed in space, where speed and environmental conditions vastly improve sensitivity. Orbiting sensors tap into ...
Dec. 3, 2025 Earth’s orbit is getting crowded with broken satellites and leftover rocket parts. Researchers say the solution is to build spacecraft that can be repaired, reused, or recycled instead of abandoned. They also want new tools to collect old debris ...
Dec. 2, 2025 A UC Irvine team uncovered a never-before-seen quantum phase formed when electrons and holes pair up and spin in unison, creating a glowing, liquid-like state of matter. By blasting a custom-made material with enormous magnetic fields, the ...
Nov. 23, 2025 A massive solar storm in May 2024 gave scientists an unprecedented look at how Earth’s protective plasma layer collapses under intense space weather. With the Arase satellite in a perfect observing position, researchers watched the plasmasphere ...
Nov. 21, 2025 New observations show that asteroid 1998 KY26 is a mere 11 meters across and spinning twice as fast as previously thought. The discovery adds complexity to Hayabusa2’s 2031 mission but also heightens scientific interest. The asteroid’s ...
Nov. 17, 2025 Scientists built a tiny clock from single-electron jumps to probe the true energy cost of quantum timekeeping. They discovered that reading the clock’s output requires vastly more energy than the clock uses to function. This measurement process ...
Nov. 16, 2025 Researchers combined deep learning with high-resolution physics to create the first Milky Way model that tracks over 100 billion stars individually. Their AI learned how gas behaves after supernovae, removing one of the biggest computational ...
Nov. 16, 2025 Dark matter may be invisible, but scientists are getting closer to understanding whether it follows the same rules as everything we can see. By comparing how galaxies move through cosmic gravity wells to the depth of those wells, researchers found ...
Nov. 13, 2025 Researchers engineered “gyromorphs,” a new type of metamaterial that combines liquid-like randomness with large-scale structural patterns to block light from every direction. This innovation solves longstanding limitations in quasicrystal-based ...
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Dec. 22, 2025 Black holes are among the most extreme objects in the universe, and now scientists can model them more accurately than ever before. By combining Einstein’s gravity with realistic behavior of light ...
Dec. 21, 2025 By studying tiny distortions in the shapes of distant galaxies, scientists mapped dark matter and dark energy across one of the largest sky surveys ever assembled. Their results back the standard ...
Dec. 20, 2025 An instrument aboard NASA’s Europa Clipper spacecraft captured rare ultraviolet observations of an interstellar comet while Earth-based telescopes were blinded by the Sun. The spacecraft’s unique ...
Dec. 20, 2025 For years, scientists thought Saturn’s moon Titan hid a global ocean beneath its frozen surface. A new look at Cassini data now suggests something very different: a thick, slushy interior with ...
Dec. 19, 2025 Cosmic “touchdown airbursts” — explosions of comets or asteroids above Earth’s surface — may be far more common and destructive than previously thought, according to new research. Unlike ...
Dec. 18, 2025 Astronomers have detected spacetime itself being dragged and twisted by a spinning black hole for the first time. The discovery, seen during a star’s violent destruction, confirms a prediction made ...
Dec. 17, 2025 A mysterious cloud of ultra-hot dust around Kappa Tucanae A may finally have an explanation: a hidden companion star. The star’s extreme orbit carries it straight through the dust zone, strongly ...
Dec. 16, 2025 Ramanujan’s elegant formulas for calculating pi, developed more than a century ago, have unexpectedly resurfaced at the heart of modern physics. Researchers at IISc discovered that the same ...
Dec. 16, 2025 Physicists have found a clever way to detect the elusive Unruh effect without extreme accelerations. By using atoms that emit light cooperatively between mirrors, acceleration subtly shifts when a ...
Dec. 15, 2025 A new theory proposes that the universe’s fundamental forces and particle properties may arise from the geometry of hidden extra dimensions. These dimensions could twist and evolve over time, ...