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
September 16, 2026
Sep. 13, 2026 Scientists have engineered yeast to turn PET plastic and agricultural waste into ingredients for protein-rich, 3D-printed cookies called µBites. Developed partly for NASA’s Deep Space Food Challenge, the system can produce proteins, fats, ...
Sep. 2, 2026 Solar sails pushed by powerful lasers could reach incredible speeds, but relativity may eventually make the light itself work against them. At around 75% of the speed of light, scattered photons can begin creating drag, adding a surprising obstacle ...
Sep. 1, 2026 NASA has brought two of Swift’s telescopes back online after technical problems derailed a commercial mission intended to rescue the aging observatory by raising its orbit. With atmospheric drag pulling the spacecraft downward faster than ...
Aug. 31, 2026 NASA’s Roman Space Telescope has launched on a million mile journey to L2, where it will scan huge portions of the cosmos for clues about dark matter, dark energy, and distant worlds. With survey ...
Aug. 28, 2026 NASA’s Roman Space Telescope will combine Hubble-like detail with a field of view 100 times larger, giving astronomers a sweeping new way to explore the cosmos. Its observations could uncover hidden planets, map billions of cosmic objects, and ...
Aug. 26, 2026 NASA has successfully tested a system that allows satellites to navigate without GPS by using other spacecraft and debris as landmarks in orbit. In just three days, FALCON also improved the known orbits of more than 200 space objects completely ...
Aug. 26, 2026 NASA’s Roman Space Telescope is now enclosed inside its Falcon Heavy fairing and nearly ready for launch. Its mission could uncover thousands of exoplanets while helping scientists investigate dark matter, dark energy, and the accelerating ...
Aug. 24, 2026 NASA’s Roman Space Telescope has been cleared for final launch preparations ahead of a targeted August 30 liftoff aboard SpaceX’s Falcon Heavy. The powerful new observatory will probe cosmic expansion, the history of the universe, and distant ...
Aug. 20, 2026 A discarded SpaceX Falcon 9 stage crashed into the Moon on Aug. 5, leaving behind a newly formed crater about 60 feet wide. NASA’s Lunar Reconnaissance Orbiter captured detailed images showing bright and dark streaks of debris blasted across the ...
Aug. 12, 2026 Researchers have found a clever new way to map a part of Earth’s upper atmosphere that is notoriously difficult to observe. Using orbital data from roughly 1,200 Starlink satellites, they ...
Aug. 11, 2026 NASA is assembling the foundations of a future Moon Base through a wave of robotic missions and powerful new commercial landers. More than 20 landings are planned through 2029, testing everything from precision landings and lunar communications to ...
Aug. 10, 2026 NASA engineers have found a clever way to squeeze more life out of Voyager 2, nearly half a century after it left Earth. In an operation nicknamed the “Big Bang,” the team simultaneously shut down certain power-hungry hardware and switched to ...
Latest Headlines
updated 12:56 pm ET
Sep. 16, 2026 Venus may have once had a moon, but new research suggests the planet’s incredibly slow rotation could have doomed it. Computer simulations showed that instead of gradually drifting away like ...
Sep. 16, 2026 A new study suggests Earth formed almost entirely from material in the inner Solar System, challenging the idea that water-rich material from beyond ...
Sep. 15, 2026 The James Webb Space Telescope has revealed surprising changes in the rings around Chariklo, a small object orbiting between Saturn and Uranus. Over ...
Sep. 15, 2026 Astronomers have discovered that winds from a supermassive black hole are about 100 times more powerful than previously thought. XRISM observations ...
Sep. 13, 2026 A massive worldwide survey of physicists has revealed surprisingly little agreement about some of the universe’s biggest mysteries. No majority backed the standard cosmological model, a leading ...
Sep. 12, 2026 A century-old mystery in Venus’s clouds just became more intriguing, as scientists calculated how strongly the unidentified material behind its dark ultraviolet patterns must absorb light. The ...
Sep. 11, 2026 Scientists have discovered that Mercury’s surface contains far less silicon dioxide than previously thought, pointing to an unexpectedly hot volcanic past. The finding suggests ancient lava may ...
Sep. 11, 2026 Unconventional quantum theories may imply that time itself has a tiny fundamental uncertainty, placing an ultimate limit on how precisely any clock could measure it. The effect is far beyond current ...
Sep. 10, 2026 Scientists have discovered that the Moon-forming collision may have depended heavily on how hot and physically strong early Earth and Theia were. New simulations found that some impacts create the ...
Sep. 9, 2026 Two major alien-life announcements in 2025 generated enormous excitement, but most astrobiologists remained unconvinced. Only 6.6% of surveyed experts thought possible biological molecules on K2-18b ...