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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
June 11, 2026
June 11, 2026 Scientists found that transfer learning can make the search for new physics in the universe much faster, slashing the need for expensive simulations. Yet the approach can backfire when AI relies too heavily on familiar patterns, potentially missing ...
June 10, 2026 MIT researchers have shown that one fuel can power both chemical and electric spacecraft thrusters, potentially transforming what small satellites can do. The approach combines quick bursts of speed with highly efficient long-range propulsion in a ...
June 8, 2026 NASA says a long-running air leak aboard the ISS recently worsened, leading engineers to investigate new suspected crack locations and consider a riskier repair strategy. Astronauts were temporarily moved into a safe haven as a precaution before the ...
June 6, 2026 A lightweight new X-ray telescope could finally give scientists something they’ve never had before: a complete chemical map of the Moon. Researchers used detailed mission simulations to show that a compact telescope orbiting the Moon could ...
June 6, 2026 NASA’s PExT terminal has shown that spacecraft can seamlessly communicate through multiple government and commercial networks, a major step beyond traditional single-network systems. The mission is now expanding to test new capabilities that could ...
June 5, 2026 Scientists have proposed a new method for finding tightly bound supermassive black hole pairs by searching for stars that flash repeatedly as their light is magnified by the black holes’ gravity. The timing and brightness of these bursts could ...
May 21, 2026 Mysterious red auroras spotted over Japan were found reaching astonishingly high altitudes, even during space storms considered relatively mild. The discovery suggests hidden solar activity may be ...
May 18, 2026 NASA’s Nancy Grace Roman Space Telescope is now aiming for an earlier launch in September 2026. Designed to explore dark matter, dark energy, and distant exoplanets, the telescope will capture massive, ultra-detailed surveys of the cosmos using ...
May 15, 2026 NASA is testing a next-generation space computer chip that could give spacecraft the ability to operate far more independently in deep space. The radiation-hardened processor is showing performance levels hundreds of times beyond current spaceflight ...
May 15, 2026 NASA’s Roman Space Telescope could expose a vast hidden population of neutron stars lurking unseen across the Milky Way. By detecting subtle shifts in starlight caused by gravity, the mission may ...
May 12, 2026 Astronomers using NASA’s James Webb Space Telescope have created the clearest map yet of the universe’s “cosmic web” — the enormous hidden structure that connects galaxies across space. By ...
May 11, 2026 NASA’s Psyche spacecraft is about to pull off a dramatic close flyby of Mars, skimming just 2,800 miles above the planet to get a powerful gravitational boost on its journey to the mysterious metal-rich asteroid Psyche. The maneuver will save ...
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June 11, 2026 NASA has selected the Artemis III crew for a high-stakes 2027 mission designed to test the future of lunar exploration. Astronauts will launch aboard ...
June 11, 2026 JWST has revealed dramatic differences between the dawn and dusk regions of the scorching exoplanet WASP-121 b. Fierce winds appear to carry heat from the planet’s permanent dayside, making the ...
June 9, 2026 The mysterious Amaterasu particle may not be a proton at all. New research suggests that some of the most extreme cosmic rays could be ultraheavy atomic nuclei, heavier than iron, which are better ...
June 8, 2026 Astronomers have spent years searching for a possible hidden giant planet far beyond Neptune. Unusual orbits among distant Kuiper Belt objects have ...
June 8, 2026 What if our biggest idea about reality is built on a hidden misunderstanding? A new philosophical look at space-time challenges the popular view that the past, present, and future all exist together ...
June 5, 2026 Scientists have uncovered a surprising force that may help explain how binary star systems form so quickly. New supercomputer simulations show that magnetic fields surrounding newborn stars can act ...
June 4, 2026 NASA's James Webb Space Telescope has uncovered unusual chemistry in interstellar comet 3I/ATLAS, including the first direct detection of methane on ...
June 3, 2026 June's night sky delivers several must-see events, starting with a close encounter between Venus and Jupiter after sunset. Mercury joins the pair to form a rare three-planet lineup, while the Moon ...
June 2, 2026 Astronomers have finally cracked the mystery behind a strange class of repeating cosmic signals that has baffled scientists for years. Using ...
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