PlutoPluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest known trans-Neptunian object by volume, by a small margin, but is slightly less massive than Eris. Like other Kuiper belt objects, Pluto is made primarily of ice and rock and is much smaller than the inner planets. Pluto has only one sixth the mass of Earth's moon, and one third its volume.
Tunguska eventThe Tunguska event (occasionally also called the Tunguska incident) was an approximately 12-megaton explosion that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate (now Krasnoyarsk Krai), Russia, on the morning of 30 June 1908. The explosion over the sparsely populated East Siberian taiga flattened an estimated 80 million trees over an area of of forest, and eyewitness reports suggest that at least three people may have died in the event.
Solar SystemThe Solar System is the gravitationally bound system of the Sun and the objects that orbit it. The largest of such objects are the eight planets, in order from the Sun: four terrestrial planets named Mercury, Venus, Earth and Mars, two gas giants named Jupiter and Saturn, and two ice giants named Uranus and Neptune. The terrestrial planets have a definite surface and are mostly made of rock and metal. The gas giants are mostly made of hydrogen and helium, while the ice giants are mostly made of 'volatile' substances such as water, ammonia, and methane.
MeteoriteA meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and radiate energy. It then becomes a meteor and forms a fireball, also known as a shooting star; astronomers call the brightest examples "bolides".
Voyager 2Voyager 2 is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach gas giants Jupiter and Saturn but enabled further encounters with ice giants Uranus and Neptune. Voyager 2 remains the only spacecraft to have visited either of the ice giant planets.
Orbital eccentricityIn astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values between 0 and 1 form an elliptic orbit, 1 is a parabolic escape orbit (or capture orbit), and greater than 1 is a hyperbola. The term derives its name from the parameters of conic sections, as every Kepler orbit is a conic section.
ProtoplanetA protoplanet is a large planetary embryo that originated within a protoplanetary disc and has undergone internal melting to produce a differentiated interior. Protoplanets are thought to form out of kilometer-sized planetesimals that gravitationally perturb each other's orbits and collide, gradually coalescing into the dominant planets. A planetesimal is an object formed from dust, rock, and other materials, measuring from meters to hundreds of kilometers in size.
MeteoroidA meteoroid (ˈmiːtiərɔɪd) is a small rocky or metallic body in outer space. Meteoroids are distinguished as objects significantly smaller than asteroids, ranging in size from grains to objects up to a meter wide. Objects smaller than meteoroids are classified as micrometeoroids or space dust. Most are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars. A meteor or shooting star is the visible passage of a meteoroid, comet, or asteroid entering Earth's atmosphere.
Impact eventAn impact event is a collision between astronomical objects causing measurable effects. Impact events have physical consequences and have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effect. When large objects impact terrestrial planets such as the Earth, there can be significant physical and biospheric consequences, though atmospheres mitigate many surface impacts through atmospheric entry.
JupiterJupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, and slightly less than one one-thousandth the mass of the Sun. Jupiter is the third brightest natural object in the Earth's night sky after the Moon and Venus, and it has been observed since prehistoric times. It was named after Jupiter, the chief deity of ancient Roman religion.
Pioneer 10Pioneer 10 (originally designated Pioneer F) is a NASA space probe launched in 1972 that completed the first mission to the planet Jupiter. Pioneer 10 became the first of five planetary probes and 11 artificial objects to achieve the escape velocity needed to leave the Solar System. This space exploration project was conducted by the NASA Ames Research Center in California. The space probe was manufactured by TRW Inc. Pioneer 10 was assembled around a hexagonal bus with a diameter parabolic dish high-gain antenna, and the spacecraft was spin stabilized around the axis of the antenna.
Late Heavy BombardmentThe Late Heavy Bombardment (LHB), or lunar cataclysm, is a hypothesized event thought to have occurred approximately 4.1 to 3.8 billion years (Ga) ago, at a time corresponding to the Neohadean and Eoarchean eras on Earth. According to the hypothesis, during this interval, a disproportionately large number of asteroids and comets collided with the early terrestrial planets in the inner Solar System, including Mercury, Venus, Earth and Mars. These came from both post-accretion and planetary instability-driven populations of impactors.
