Reference Terms
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Planet
The International Astronomical Union defines "planet" as a celestial body that, within the Solar System that is in orbit around the Sun; has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape; and has cleared the neighbourhood around its orbit;
or within another system, it is in orbit around a star or stellar remnants; has a mass below the limiting mass for thermonuclear fusion of deuterium; and is above the minimum mass/size requirement for planetary status in the Solar System.
Our solar system is thus considered to have eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Under a separate resolution, it is also considered to have three dwarf planets: Ceres, Pluto, and Eris. There have been more than two hundred planets discovered orbiting other stars to date.
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Space & Time News
November 4, 2026
Nov. 4, 2026 NASA is exploring a daring plan to save the legendary Hubble Space Telescope from its eventual fiery plunge into Earth's atmosphere. After more than 35 years of groundbreaking discoveries, Hubble is slowly losing altitude, and without intervention, ...
Nov. 3, 2026 Europe’s Hera spacecraft has captured its first clear view of two asteroids involved in NASA’s historic 2022 experiment to redirect a potentially dangerous space rock. Now approaching the pair, Hera will investigate the mysterious aftermath of ...
Nov. 3, 2026 NASA’s Voyager 1 is approaching an extraordinary milestone nearly 50 years after its launch, even as engineers battle dwindling power and mysterious technical problems. A clever energy-saving maneuver has extended the spacecraft’s scientific ...
Nov. 2, 2026 Mysterious particles called neutrinos constantly stream through our bodies, and scientists are now detecting incredibly powerful versions arriving from distant cosmic sources using a massive ...
Nov. 2, 2026 NASA’s Perseverance rover has set a historic record by traveling 28.10 miles across Mars, farther than any vehicle has ever driven on another world. Armed with groundbreaking autonomous navigation ...
Oct. 28, 2026 NASA’s Artemis I mission has revealed that cosmic radiation near the Moon is higher than in Earth orbit, but not by as much as scientists might expect. Tiny experimental detectors also uncovered ...
Oct. 21, 2026 Scientists have cracked a 178-year-old mystery surrounding a train delayed by a solar storm, revealing that the famous incident happened in 1848 rather than 1841. The discovery rewrites the early history of space weather and highlights a threat that ...
Oct. 21, 2026 A new study tracking 13 astronauts suggests that the human heart may be surprisingly well equipped for a journey to Mars, especially with regular exercise during spaceflight. Researchers found that astronauts' hearts adapted to months of ...
Oct. 21, 2026 NASA’s Perseverance rover has shattered a historic space exploration record, traveling farther across another world than any vehicle before it. Its advanced self-driving system helped it surpass ...
Oct. 17, 2026 NASA’s Nancy Grace Roman Space Telescope has exceeded expectations after engineers made incredibly tiny adjustments to sharpen its view of the universe. By moving a mirror just one-sixteenth the width of a human hair, the team helped bring its ...
Oct. 16, 2026 SpaceX just delivered some surprisingly strange cargo to the International Space Station, including tiny brain models, 3D heart tissue, and technology for making artificial retinas in space. ...
Oct. 12, 2026 Europe's Sentinel-3C satellite has returned breathtaking images of Earth just two weeks after launch, revealing the snowy Alps, frozen Arctic islands, and brilliant turquoise Caribbean waters. Its ...
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Nov. 3, 2026 Something mysterious is disturbing Betelgeuse, and astronomers believe they have identified the culprit: a hidden companion star called Siwarha. New ...
Nov. 3, 2026 Scientists have discovered all five essential nucleobases used in DNA and RNA in pristine samples from asteroid Ryugu, revealing that key ingredients ...
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Nov. 1, 2026 NASA’s Hubble and James Webb Space Telescopes have uncovered surprising clues about the solar system’s origins by studying 27 tiny, distant objects beyond Neptune. Scientists discovered that ...
Nov. 1, 2026 A mysterious particle overlooked for decades may hold the key to why matter survived the Big Bang, allowing stars, planets, and life to exist. Scientists believe this forgotten neutrino reshaped the ...
Oct. 30, 2026 Scientists have recreated a primordial state of matter from the dawn of the universe by colliding oxygen nuclei at nearly the speed of light. The surprising results show that this exotic substance ...
Oct. 30, 2026 Scientists have created a miniature universe in the laboratory that could help answer one of the biggest mysteries in physics: What is time, and where does it come from? Using 24,000 ultracold atoms, ...
Oct. 30, 2026 A surprising discovery by astronomers using the Hubble Space Telescope is challenging a leading explanation for how the early universe emerged from a dense fog of hydrogen roughly 13 billion years ...
Oct. 30, 2026 Two astronauts completed a 7-hour, 11-minute spacewalk to install a new solar array on the International Space Station, bringing NASA one step closer to a major power upgrade. Once the final array is ...
Oct. 29, 2026 Astronomers have solved a 170-year-old planetary mystery in a nearby two-star system, discovering that a mysterious wobble was caused by stellar ...