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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
October 6, 2025
Oct. 6, 2025 — ESA has inaugurated a powerful new 35-meter deep space antenna at its New Norcia site in Western Australia, marking a major boost to Europe’s ability to communicate with spacecraft exploring the ...
Oct. 3, 2025 — Researchers have designed a new type of gravitational wave detector that operates in the milli-Hertz range, a region untouched by current observatories. Built with optical resonators and atomic clocks, the compact detectors can fit on a lab table ...
Sep. 30, 2025 — A new boron-rich compound, manganese diboride, delivers much higher energy density than current solid-rocket materials while remaining stable until intentionally ignited. Its power comes from an unusual, strained atomic structure formed during ...
Sep. 18, 2025 — Astronomers have long relied on supercomputers to simulate the immense structure of the Universe, but a new tool called Effort.jl is changing that. By mimicking the behavior of complex cosmological models, this emulator delivers results with the ...
Sep. 18, 2025 — Faint hydrogen signals from the cosmic Dark Ages may soon help determine the mass of dark matter particles. Simulations suggest future Moon-based observatories could distinguish between warm and cold dark matter, providing long-sought answers about ...
Sep. 17, 2025 — A new AI model from NYU Abu Dhabi predicts solar wind days in advance with far greater accuracy than existing methods. By analyzing ultraviolet solar images, it could help protect satellites, navigation systems, and power grids from disruptive space ...
Sep. 15, 2025 — The booming space industry has filled the skies with rockets and satellites, but this rapid expansion comes with a hidden danger: slowing the recovery of the ozone layer. Rocket launches and burning space debris release chlorine, soot, and metals ...
Sep. 11, 2025 — NASA’s Magnetospheric Multiscale Mission has uncovered surprising behavior of pickup ions drifting through the solar wind near Earth. These particles, once thought to be minor players, appear capable of generating waves and influencing how the ...
Sep. 10, 2025 — Physicists have unveiled a new superconducting detector sensitive enough to hunt dark matter particles smaller than electrons. By capturing faint photon signals, the device pushes the search into uncharted ...
Sep. 9, 2025 — Scientists caution that asteroid deflection must be precise, as striking the wrong spot risks sending it through a gravitational keyhole that sets up a future collision with Earth. Using lessons from NASA’s DART mission, researchers are developing ...
Aug. 25, 2025 — Scientists using Google’s quantum processor have taken a major step toward unraveling the deepest mysteries of the universe. By simulating fundamental interactions described by gauge theories, the ...
Aug. 22, 2025 — Astronomers using AI have captured a once-in-a-lifetime cosmic event: a massive star’s violent death triggered by its black hole companion. The explosion, known as SN 2023zkd, not only produced a brilliant supernova but also shocked scientists by ...
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Oct. 6, 2025 — Astronomers have found the most distant and energetic “odd radio circle” ever detected — a massive double-ringed radio structure nearly 10 billion years old. The discovery, made with the help ...
Oct. 6, 2025 — NASA’s James Webb Space Telescope has unveiled a breathtaking cosmic landscape that looks more like a scene from fantasy than reality. What appears to be a glowing mountain peak shrouded in mist is ...
Oct. 6, 2025 — Scientists may have finally uncovered the mystery behind ultra-high-energy cosmic rays — the most powerful particles known in the universe. A team from NTNU suggests that colossal winds from ...
Oct. 6, 2025 — October’s night sky is set to dazzle, featuring a radiant supermoon, the fiery Draconid meteor shower, and the sparkling Orionids. As the full moon reaches its largest and brightest on October 6, ...
Oct. 3, 2025 — Astronomers have uncovered a runaway feeding frenzy in a rogue planet drifting freely through space, devouring six billion tonnes of gas and dust every second. Located 620 light-years away in the ...
Oct. 3, 2025 — New lunar samples from the far side reveal it formed from cooler magma than the near side, confirming the Moon’s interior is not uniform. Researchers suggest fewer heat-producing elements on the ...
Oct. 2, 2025 — Fresh analysis of Cassini data has revealed new complex organic molecules inside ice grains spewing from Enceladus. These discoveries strengthen the case that the moon’s underground ocean hosts ...
Oct. 1, 2025 — The LUX-ZEPLIN detector is breaking new ground in the hunt for dark matter, setting unprecedented limits on WIMP particles. Its results not only narrow the possibilities for dark matter but also open ...
Oct. 1, 2025 — For decades, Uranus baffled scientists because it seemed to have no internal heat. Now, new computer modeling shows the planet actually emits more energy than it receives from the Sun. This subtle ...
Oct. 1, 2025 — Perseverance rover data shows Jezero Crater once held a calm lake, leaving behind mudstones rich in organic-linked minerals. The presence of iron-phosphate and iron-sulfide nodules suggests processes ...