Pluto had been officially listed among the planets since it was discovered in 1930 orbiting beyond Neptune, but in 1992 an icy object was discovered still farther from the Sun than Pluto. You can make it easier for us to review and, hopefully, publish your contribution by keeping a few points in mind: Encyclopaedia Britannica articles are written in a neutral, objective tone for a general audience
Planet Order from the Sun; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune Our knowledge of our solar system is extensive but it is far from complete. Please visit our Astronomy news section which gives news, notes and general observations, we also have an interactive tour of the solar system (loads in a new window) All planets can be seen with a small telescope or binoculars and private observatories continue to provide useful information
An Overview of the Solar System, it's alignment and pictures
The eight bodies officially categorized as planets are often further classified in several ways: by composition: terrestrial or rocky planets: Mercury, Venus, Earth, and Mars: The terrestrial planets are composed primarily of rock and metal and have relatively high densities, slow rotation, solid surfaces, no rings and few satellites. With a few exceptions, the planetary satellites orbit in the same sense as the planets and approximately in the plane of the ecliptic but this is not generally true for comets and asteroids
The Sun is just one of hundreds of billions of stars contained in the Milky Way galaxy and there are hundreds of billions of galaxies in the observable universe. For example, NASA's Dawn mission was designed to study the two largest objects in the asteroid belt to learn more about the conditions and processes of the early solar system; Dawn has already collected data from Vesta and will reach Ceres in 2015
Aliens hanging out in the Kuiper Belt? We could see the light from their cities
Starry surprise in the bulge: encounter of a halo passerby July 22, 2015 A team led by Andrea Kunder from the Leibniz Institute for Astrophysics Potsdam (AIP) measured the velocity of a sample of 100 old RR Lyrae stars thought to reside in the Galactic bulge, the central group of stars found in ... But Loeb has posed that possibly planets ejected from other parent stars in our galaxy may have traveled to the edge of our Solar System and ended up residing there
Dwarf Planets: Classification, Discovery, Definition, Kuiper Belt - Windows to the Universe
Since we don't know the actual sizes or shapes of many of the objects we've found (because they are so far away), we can't yet determine whether they are actually dwarf planets or not. Considered a planet, though a rather odd one, from its discovery in 1930 until 2006, it was...moreEris - a dwarf planetEris is a dwarf planet in our Solar System
These compounds arrived in the inner planets after their initial formation, most likely brought by impacts of planetesimals formed in the outskirts of the solar system (Q: What was Jupiter's role in bringing water to Earth?). Formation of moon systems As the early jovian planets captured large amounts of gas, the same process that formed the solar nebula -- contraction, spinning, flattening and heating -- formed similar but smaller disks of material around these planets
Planets in the Solar System
The Earth has a solid core of iron surrounded by a liquid outer core that generates a magnetic field that also helps protect life on Earth from the radiation of space. Saturn has been visited by spacecraft 4 times: Pioneer 11, Voyager 1 and 2 were just flybys, but Cassini has actually gone into orbit around Saturn and has captured thousands of images of the planet and its moons
Due to the distance away from us there is still a lot to be discovered about the Kuiper belt but we believe there to be hundreds of thousands of icy bodies that are larger than 100 km in diameter and more than a trillion comets. Pluto (one thought to be the ninth planet in our solar system but since relegated to dwarf planet status) is the most famous object that is found in the Kuiper belt
Solar System Fluff
Jupiter and perhaps Saturn tend to deflect long period comets completely out of the solar system (or gobble them up as Jupiter did with Shoemaker Levy-9). The comets passing close to a jovian planet are deflected by the planet's gravity into an orbit with a shorter period, only decades to a few thousand years long
Solar System
Studies of T Tauri stars, young, pre-fusing solar mass stars believed to be similar to the Sun at this point in its evolution, show that they are often accompanied by discs of pre-planetary matter. The largest star within ten light years is Sirius, a bright main sequence star roughly twice the Sun's mass and orbited by a white dwarf called Sirius B
Cosmic Distance Scales - The Solar System
This leads to the idea of a 'habitable zone' --- for a star of a given brightness, you can determine the approximate range of distances a planet has to be for liquid water to exist. Although their origin is not completely understood, it is thought that Scattered Disc Objects were previously members of the Kuiper Belt, which got ejected into eccentric, scattered orbits through close encounters with Neptune
The Solar System, summary of 8 planets, Kuiper Objects, Oort Clouds: Etacude.com
Oort (1900-1992), a Dutch astronomer, found that all comets orbit the Sun and none came from interstellar space and there is no preferential direction from which comets come
The crux is that the current def sucks and the circumstances that led to the new def also suck; therefore, the issue needs to be reopened where real planetary scientists have input into a better def of a planet. There IS an ongoing debate between dynamicists, who believe a spherical celestial object that is not a star must be the dominant thing in its orbit to be a planet, and geophysicists, who believe that a spherical celestial object that is not a star is a planet, whether or not it dominates its orbit
If the relation between the number of objects and size for KBOs is similar to that of asteroids, that implies a total Kuiper belt population of more than 100 billion sources larger than 1 km in diameter. The Nice model provides a reasonable representation of the hot component of the Kuiper belt but is less successful at producing the resonant objects and does not provide for a cold classical component
Instead, the plasma ions have the right amount of energy to simply "sandblast" the topmost layer of the surface -- which is perhaps a millimeter thick -- right off. NASA's New Horizons mission will pass through the Kuiper Belt region beyond Neptune's orbit in 2014, getting a good look at Pluto and its largest moon Charon in 2015, and later, if all goes well, one or two other objects
In July 2005, astronomers announced the discovery of an object in the Kuiper Belt thought to be larger than Pluto, though subsequent observations revealed it was slightly smaller. Scientists estimate that thousands of bodies more than 62 miles (100 km) in diameter travel around the sun within this belt, along with trillions of smaller objects, many of which are short-period comets
Kuiper belt - definition of Kuiper belt by The Free Dictionary
(Astronomy) a region of the solar system beyond the orbit of Neptune, some 30-1000 astronomical units from the sun, containing up to one thousand million icy planetesimals or comet nuclei
It is a region where the planet-building process was stopped in before any large objects were formed; there are only primitive remnants from the early accretion disk of the solar system, 4.5 billion years ago. Occasionally, one of the icy objects in the Kuiper belt is disturbed by the gravitational forces of one of the gas giant planets, causing it to approach Neptune, which sometimes propels the small object into a new, very elliptical solar orbit, where it may eventually approach the Sun (and near the Sun, the characteristic comet tail is visible)
The short-period comets are thought to originate in the Kuiper Belt, an area outside Neptune's orbit (from about 30 to 50 AU) that has many icy comet-like objects. The objects in the Oort cloud probably formed closer to the Sun, around the present day orbits of Uranus and Neptune, and were then pushed out to their current positions by gravitational interactions with the planets
Each photo is a 5-hour exposure of a piece of sky carefully selected such that it is nearly devoid of background stars and galaxies that could mask the elusive comet. Kuiper's hypothesis was reinforced in the early 1980s when computer simulations of the solar system's formation predicted that a disk of debris should naturally form around the edge of the solar system
The object, temporarily designated 2003UB313 and later named Eris, orbits the sun about once every 560 years, its distance varying from about 38 to 98 AU. In contrast, short-period comets take less than 200 years to orbit the sun and they travel approximately in the plane in which most of the planets orbit
BBC Solar System - The Kuiper Belt contains millions of icy objects
The Cassini-Huygens probe, launched in 1997, made a close flyby of Saturn's moon Phoebe and answered a fundamental question about this unusual moon's origins. Although many asteroids are composed primarily of rock and metal, most Kuiper belt objects are composed largely of frozen volatiles (termed "ices"), such as methane, ammonia and water
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