Reference Terms
from Wikipedia, the free encyclopedia
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.
Related Stories
1
2
Space & Time News
June 9, 2025
June 3, 2025 — Supermassive black holes might naturally replicate the colossal energies of man-made particle colliders possibly even revealing dark matter offering a cosmic shortcut to discoveries that would ...
June 3, 2025 — Astronomers have revealed new research showing that millions of new solar system objects are likely to be detected by a brand-new facility, which is expected to come online later this ...
June 3, 2025 — Scientists have identified a new source of energetic particles near the Sun. These definitive observations were made by instruments aboard NASA's Parker Solar Probe, which detected the powerful phenomena as the spacecraft dipped in and out of the ...
June 2, 2025 — Tracing the origin of an ultra-hot exoplanet: The chemical composition of WASP-121b suggests that it formed in a cool zone of its natal disc, comparable to the region of gas and ice giants in our Solar System. Methane indicates unexpected ...
June 2, 2025 — Researchers have engineered a laser device smaller than a penny that they say could power everything from the LiDAR systems used in self-driving vehicles to gravitational wave detection, one of the most delicate experiments in existence to observe ...
May 30, 2025 — A series of studies sheds light on the origins and characteristics of intermediate-mass black ...
May 29, 2025 — The process of necrosis, a form of cell death, may represent one of the most promising ways to change the course of human aging, disease and even space travel, according to a new ...
May 21, 2025 — A multi-sensor detection of an intense gamma-ray flash, which occurs when two lightning leaders collided, has been observed. Observations across a wide radiation spectrum enabled precise measurement of the electric current produced during this ...
May 2, 2025 — Astronomers have explained how a galaxy cluster maintains its heat, despite emitting X-rays that cool the hot gas at its center. The group discovered the existence of a fast-moving, high-temperature ...
May 28, 2025 — A team of international astronomers have discovered a new cosmic object emitting both radio waves and ...
May 28, 2025 — A series of experiments support spectral data recently collected by the James Webb Space Telescope that found evidence that the icy surface of Jupiter's moon Europa is constantly changing. Europa's surface ice is crystallizing at different rates in ...
May 28, 2025 — Scientists have observed anyons -- quasiparticles that differ from the familiar fermions and bosons -- in a one-dimensional quantum system for the first time. The results may contribute to a better ...
Latest Headlines
updated 12:56 pm ET
June 7, 2025 — An international team of scientists has unveiled the largest and most detailed map of the universe ever created using the James Webb Space Telescope, ...
'Raindrops in the Sun's Corona': New Adaptive Optics Shows Stunning Details of Our Star's Atmosphere
May 27, 2025 — Scientists have produced the finest images of the Sun's corona to date. To make these high-resolution images and movies, the team developed a new ...
May 23, 2025 — Scientists may have solved the mystery of why the moon shows ancient signs of magnetism although it has no magnetic field today. An impact, such as from a large asteroid, could have generated a cloud ...
May 21, 2025 — Scientists have discovered how solar activity affects the velocity distribution and evolution of helium pickup ...
May 22, 2025 — Astronomers have observed a massive and extremely active barred spiral galaxy in the early Universe and found that it has important similarities and differences with modern galaxies. This improves ...
May 22, 2025 — The puzzling behavior of Titan's atmosphere has been revealed. The team has shown that the thick, hazy atmosphere of Saturn's largest moon doesn't spin in line with its surface, but instead wobbles ...
May 21, 2025 — The fundamental building blocks for planet formation can exist even in environments with extreme ultraviolet radiation, according to a new ...
May 20, 2025 — In the intriguing realm of star-forming galaxies, the key factor isn't the total amount of gas but rather its strategic distribution within the ...
May 21, 2025 — Astronomers have witnessed for the first time a violent cosmic collision in which one galaxy pierces another with intense radiation. Their results show that this radiation dampens the wounded ...
May 20, 2025 — Astronomers have filled a large gap in knowledge about Mars' water cycle. Their research on water percolating from surface to aquifer could change the picture of what early Mars was like, suggesting ...