The principal component of the Solar System is the Sun, a G2 main-sequence star that contains 99.86% of the system's known mass and dominates it gravitationally. The Sun's four largest orbiting bodies, the giant planets, account for 99% of the remaining mass, with Jupiter and Saturn together comprising more than 90%. The remaining objects of the Solar System (including the four terrestrial planets, the dwarf planets, moons, asteroids, and comets) together comprise less than 0.002% of the Solar System's total mass. Most large objects in orbit around the Sun lie near the plane of Earth's orbit, known as the ecliptic.
Structure and composition
Solar System
Solar System | Structure and composition
Sun, the giant planets, four terrestrial planets, the dwarf planets, moons, asteroids, and comets. The eight planets, the dwarf planets and small Solar System bodies, the moons Minor planets can be dwarf planets, asteroids, trojans, centaurs, Kuiper belt objects, and other trans-Neptunian objects. It consists of objects that orbit the Sun directly, the largest are the eight planets, with the remainder being smaller objects, the dwarf planets and small Solar System bodies.
where is sedna located in the solar system
user
In the outer reaches of the Solar System.
assistant
who discovered it?
user
Michael Brown (Caltech), Chad Trujillo (Gemini Observatory), and David Rabinowitz (Yale University).
assistant
who gave it it's name?
user
Michael Brown.
assistant
what does it look like?
user
It is a large planetoid, surface is redd.
assistant
the system mentioned above, what does it consist of?
user
The principal component of the Solar System is the Sun, a G2 main-sequence star that contains 99.86% of the system's known mass and dominates it gravitationally. The Sun's four largest orbiting bodies, the giant planets, account for 99% of the remaining mass, with Jupiter and Saturn together comprising more than 90%. The remaining objects of the Solar System (including the four terrestrial planets, the dwarf planets, moons, asteroids, and comets) together comprise less than 0.002% of the Solar System's total mass. Most large objects in orbit around the Sun lie near the plane of Earth's orbit, known as the ecliptic.
Solar System | Structure and composition
The overall structure of the charted regions of the Solar System consists of the Sun, four relatively small inner planets surrounded by a belt of mostly rocky asteroids, and four giant planets surrounded by the Kuiper belt of mostly icy objects. Astronomers sometimes informally divide this structure into separate regions. The inner Solar System includes the four terrestrial planets and the asteroid belt. The outer Solar System is beyond the asteroids, including the four giant planets. Since the discovery of the Kuiper belt, the outermost parts of the Solar System are considered a distinct region consisting of the objects beyond Neptune.
Solar System | Structure and composition
The Solar System comprises the Sun and the objects that orbit it, either directly or indirectly. Solar System may also refer to:
Solar System (disambiguation) | Introduction
The composition of the Solar System is similar to that of many other stars, and aside from small anomalies it can be assumed to have formed from a solar nebula that had a uniform composition, and the composition of the Sun's photosphere is similar to that of the rest of the Solar System. The composition of the photosphere is determined by fitting the absorption lines in its spectrum to models of the Sun's atmosphere. By far the largest two elements by fraction of total mass are hydrogen (74.9%) and helium (23.8%), with all the remaining elements contributing just 1.3%. There is a general trend of exponential decrease in abundance with increasing atomic number, although elements with even atomic number are more common than their odd-numbered neighbors (the Oddo–Harkins rule).
Geochemistry | Solar System
The Solar System also contains smaller objects. The asteroid belt, which lies between the orbits of Mars and Jupiter, mostly contains objects composed, like the terrestrial planets, of rock and metal. Beyond Neptune's orbit lie the Kuiper belt and scattered disc, which are populations of trans-Neptunian objects composed mostly of ices, and beyond them a newly discovered population of sednoids. Within these populations, some objects are large enough to have rounded under their own gravity, though there is considerable debate as to how many there will prove to be. Such objects are categorized as dwarf planets. The only certain dwarf planet is Pluto, with another trans-Neptunian object, Eris, expected to be, and the asteroid Ceres at least close to being a dwarf planet.
Solar System | Introduction
The planets are very close to the ecliptic, whereas comets and Kuiper belt objects are frequently at significantly greater angles to it. As a result of the formation of the Solar System planets, and most other objects, orbit the Sun in the same direction that the Sun is rotating (counter-clockwise, as viewed from above Earth's north pole). There are exceptions, such as Halley's Comet. Most of the larger moons orbit their planets in this "prograde" direction (with Triton being the largest "retrograde" exception) and most larger objects rotate themselves in the same direction (with Venus being a notable "retrograde" exception).
Solar System | Structure and composition
Analysis of precovery observations in the visible spectrum between 2002 and 2007 show that it may be amongst the reddest objects in the Solar System, being more than 1.5 magnitudes fainter in the G (green) filtered versus the R (red) filtered images, which may offer some clues about its composition and origin "(also see color indices)". This is expected from a fairly small "orbitally unexcited" cold Classical Kuiper belt object as they are generally mostly red. The cold populations distance does not vary from the Sun very much so their surfaces are older, more irradiated, and covered in tholins. There is a chance it accreted in basically the same orbit it has today.
420356 Praamzius | Physical characteristics
Asteroids except for the largest, Ceres, are classified as small Solar System bodies and are composed mainly of refractory rocky and metallic minerals, with some ice. They range from a few metres to hundreds of kilometres in size. Asteroids smaller than one meter are usually called meteoroids and micrometeoroids (grain-sized), depending on different, somewhat arbitrary definitions. The asteroid belt occupies the orbit between Mars and Jupiter, between from the Sun. It is thought to be remnants from the Solar System's formation that failed to coalesce because of the gravitational interference of Jupiter. The asteroid belt contains tens of thousands, possibly millions, of objects over one kilometre in diameter.
Solar System | Asteroid belt
The Solar System consists of an inner region of small rocky planets and outer region of large gas giants. However, other planetary systems can have quite different architectures. Studies suggest that architectures of planetary systems are dependent on the conditions of their initial formation. Many systems with a hot Jupiter gas giant very close to the star have been found. Theories, such as planetary migration or scattering, have been proposed for the formation of large planets close to their parent stars. At present, few systems have been found to be analogous to the Solar System with terrestrial planets close to the parent star.
Planetary system | System architectures
This section is a sampling of Solar System bodies, selected for size and quality of imagery, and sorted by volume. Some omitted objects are larger than the ones included here, notably Eris, because these have not been imaged in high quality.
Solar System | Visual summary
The four terrestrial or inner planets have dense, rocky compositions, few or no moons, and no ring systems. They are composed largely of refractory minerals, such as the silicateswhich form their crusts and mantlesand metals, such as iron and nickel, which form their cores. Three of the four inner planets (Venus, Earth and Mars) have atmospheres substantial enough to generate weather; all have impact craters and tectonic surface features, such as rift valleys and volcanoes. The term "inner planet" should not be confused with "inferior planet", which designates those planets that are closer to the Sun than Earth is (i.e.
Solar System | Inner planets
The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets, being primarily composed of rock and metal. The four outer planets are giant planets, being substantially more massive than the terrestrials. The two largest planets, Jupiter and Saturn, are gas giants, being composed mainly of hydrogen and helium; the two outermost planets, Uranus and Neptune, are ice giants, being composed mostly of substances with relatively high melting points compared with hydrogen and helium, called volatiles, such as water, ammonia and methane. All eight planets have almost circular orbits that lie within a nearly flat disc called the ecliptic.
Solar System | Introduction
The inner Solar System is the region comprising the terrestrial planets and the asteroid belt. Composed mainly of silicates and metals, the objects of the inner Solar System are relatively close to the Sun; the radius of this entire region is less than the distance between the orbits of Jupiter and Saturn. This region is also within the frost line, which is a little less than 5 AU (about 700 million km) from the Sun.
Solar System | Inner Solar System
The planet seems to be a gas giant with a low core mass (<~10M(Earth)) and a low heavy elements content (Z<~0.2).
WASP-28b | Internal structure
The models are composed of heavy-duty Styrofoam which is painted to resemble each of the planets. The Solar System is completed with smaller models of Earth, Mars, Venus, and Mercury mounted at the visitor's level. Created to be a scale model system, Earth is about the size as a soccer ball and Mercury the size of a baseball.
Virginia Air and Space Center | Our Solar System
The following outline is provided as an overview of and topical guide to the Solar System: Solar System – gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly. Of those objects that orbit the Sun directly, the largest eight are the planets (including Earth), with the remainder being significantly smaller objects, such as dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly, the moons, two are larger than the smallest planet, Mercury.
Outline of the Solar System | Introduction
Asteroids, comets, and meteoroids are all debris remaining from the nebula in which the Solar System formed 4.6 billion years ago.
Geology of solar terrestrial planets | Small Solar System bodies
The following is a list of Solar System objects by orbit, ordered by increasing distance from the Sun. Most named objects in this list have a diameter of 500 km or more. The Solar System also contains:
List of Solar System objects | Introduction
The Solar System is the gravitationally bound system of the Sun and the objects that orbit it, either directly or indirectly. Of the objects that orbit the Sun directly, the largest are the eight planets, with the remainder being smaller objects, the dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly—the moons—two are larger than the smallest planet, Mercury. The Solar System formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The vast majority of the system's mass is in the Sun, with the majority of the remaining mass contained in Jupiter.
Solar System | Introduction
Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, though helium comprises only about a tenth of the number of molecules. It may also have a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. Because of its rapid rotation, the planet's shape is that of an oblate spheroid (it has a slight but noticeable bulge around the equator). The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope.
Jupiter | Introduction
The planets were originally thought to have formed in or near their current orbits. This has been questioned during the last 20 years. Currently, many planetary scientists think that the Solar System might have looked very different after its initial formation: several objects at least as massive as Mercury were present in the inner Solar System, the outer Solar System was much more compact than it is now, and the Kuiper belt was much closer to the Sun.
Formation and evolution of the Solar System | Subsequent evolution
Terrestrial planets have numerous similarities to plutoids (objects like Pluto), which also have a solid surface, but are primarily composed of icy materials. During the formation of the Solar System, there were probably many more (planetesimals), but they have all merged with or been destroyed by the four remaining worlds in the solar nebula.
Geology of solar terrestrial planets | Introduction
The ejected outer layers will form what is known as a planetary nebula, returning some of the material that formed the Sun—but now enriched with heavier elements like carbon—to the interstellar medium.
Solar System | Formation and evolution
The four inner or terrestrial planets have dense, rocky compositions, few or no moons, and no ring systems. They are composed largely of minerals with high melting points, such as the silicates which form their solid crusts and semi-liquid mantles, and metals such as iron and nickel, which form their cores.
Geology of solar terrestrial planets | Surface geology of inner solar planets
In 2010 a transiting hot Jupiter like planet was detected. It has an measured nightside temperature of 2154 K. The planet is on unstable orbit, and expected to be engulfed by parent star after 7.5 million years from now, although measurements of orbital decay has yielded an inconclusive results as in 2020. The planetary orbit is probably aligned with the equatorial plane of the star, misalignment equal to 15°. The color of planetary atmosphere is grey.
HAT-P-23 | Planetary system
Despite this, the total mass of the asteroid belt is unlikely to be more than a thousandth of that of Earth. The asteroid belt is very sparsely populated; spacecraft routinely pass through without incident.
Solar System | Asteroid belt
Little is known about this planet, with the only characteristics known about this system are the mass of the planet and its projected separation from its host star.
MOA-2010-BLG-477L | Planetary system
Depending on composition the two planets may be around the same size, or HD 154345 b may be larger. This planet may also harbor a system of moons and rings.
HD 154345 b | Characteristics
Mercury and Venus).
Solar System | Inner planets
Afterwards, all that will remain of the Sun is a white dwarf, an extraordinarily dense object, 54% its original mass but only the size of the Earth. Initially, this white dwarf may be 100 times as luminous as the Sun is now. It will consist entirely of degenerate carbon and oxygen, but will never reach temperatures hot enough to fuse these elements. Thus the white dwarf Sun will gradually cool, growing dimmer and dimmer.
Formation and evolution of the Solar System | The Sun and planetary environments
A planetary system is a set of gravitationally bound non-stellar objects in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although such systems may also consist of bodies such as dwarf planets, asteroids, natural satellites, meteoroids, comets, planetesimals and circumstellar disks. The Sun together with the planets revolving around it, including Earth, is known as the Solar System. The term exoplanetary system is sometimes used in reference to other planetary systems. Of particular interest to astrobiology is the habitable zone of planetary systems where planets could have surface liquid water, and thus the capacity to harbor Earth-like life.
Planetary system | Introduction
Gas giants consist mostly of hydrogen and helium. The Solar System's gas giants, Jupiter and Saturn, have heavier elements making up between 3 and 13 percent of their mass. Gas giants are thought to consist of an outer layer of molecular hydrogen, surrounding a layer of liquid metallic hydrogen, with a probable molten core with a rocky composition. Jupiter and Saturn's outermost portion of the hydrogen atmosphere has many layers of visible clouds that are mostly composed of water and ammonia. The layer of metallic hydrogen makes up the bulk of each planet, and is referred to as "metallic" because the very high pressure turns hydrogen into an electrical conductor.
Giant planet | Gas giants
appears unusually bright for its size, suggesting it is made of brighter materials than the average asteroid.
2018 CB | Physical characteristics
The system contains six planets with minimum masses from 12 to 65 times Earth's (ranging in mass from roughly Uranus to Saturn) at orbital radii of 0.06, 0.13, 0.27, 0.49, 1.42 and 3.4 AU. In Solar system this set of orbits would fit within main asteroid belt. There are no planets known to be in mean-motion resonances, although it has a number of near resonances including 3c:2i:1d and 3e:2j:1f. The approximate ratios of periods of adjacent orbits are (proceeding outward): 1:5, 1:3, 1:3, 2:5, 1:5, 3:11. Since the inclination of the planets' orbits is unknown, only minimum planetary masses can presently be obtained.
HD 10180 | Orbital arrangement
It is possible that a planet in this system may have been scattered and ended up being accreted by the star, which may account for the large surface metallicity.
HD 12661 | Properties
This is a list of the lists of small Solar System bodies and dwarf planets.
Lists of small Solar System bodies | Introduction
The planets formed by accretion from this disc, in which dust and gas gravitationally attracted each other, coalescing to form ever larger bodies. Hundreds of protoplanets may have existed in the early Solar System, but they either merged or were destroyed, leaving the planets, dwarf planets, and leftover minor bodies. Due to their higher boiling points, only metals and silicates could exist in solid form in the warm inner Solar System close to the Sun, and these would eventually form the rocky planets of Mercury, Venus, Earth, and Mars. Because metallic elements only comprised a very small fraction of the solar nebula, the terrestrial planets could not grow very large.
Solar System | Formation and evolution
The size of a Solar System object can be deduced from its optical magnitude, its distance, and its albedo. Objects appear bright to Earth observers either because they are large or because they are highly reflective. If their reflectivity (albedo) can be ascertained, then a rough estimate can be made of their size. For most distant objects, the albedo is unknown, but Haumea is large and bright enough for its thermal emission to be measured, which has given an approximate value for its albedo and thus its size. However, the calculation of its dimensions is complicated by its rapid rotation.
Haumea | Size, shape, and composition
This fractionation process is the reason why the terrestrial planets and asteroid belt are relatively enriched in heavy elements in respect to the Sun or the gas planets. Certain type of meteorites, CI-chondrites, have chemical compositions that are almost identical to the solar photosphere, except for the abundances of volatiles. Because the Sun contains 99.86% of the mass of the Solar System, they are considered to have the same composition as the solar nebula (with the exception of volatile loss) and are therefore representative of the material from which the terrestrial planets, including the Earth, were formed.
Chondritic uniform reservoir | Introduction
The Sun is a G-type main-sequence star. It contains almost 99.9% of all the mass in the Solar System.
List of gravitationally rounded objects of the Solar System | Star
The planets of the Solar System are divided into two groups: the four inner planets are the terrestrial planets (Mercury, Venus, Earth and Mars), with relatively small sizes and rocky surfaces. The four outer planets are the giant planets, which are dominated by hydrogen and helium and have lower mean densities. These can be further subdivided into the gas giants (Jupiter and Saturn) and the ice giants (Uranus and Neptune) that have large icy cores. Most of our direct information on the composition of the giant planets is from spectroscopy. Since the 1930s, Jupiter was known to contain hydrogen, methane and ammonium.
Geochemistry | Giant planets
This appears to be a result of the rapid rotation and underlying symmetry of the planet. There are no oceans or landmasses to cause local heating and the rotation speed is much higher than that of Earth. There are smaller structures as well: spots of different sizes and colors. On Jupiter, the most noticeable of these features is the Great Red Spot, which has been present for at least 300 years. These structures are huge storms. Some such spots are thunderheads as well.
Giant planet | Atmospheres
All terrestrial planets in the Solar System have the same basic structure, such as a central metallic core (mostly iron) with a surrounding silicate mantle. The Earth's Moon is similar, but has a much smaller iron core; other natural satellites, such as Io, Europa, and Titan, also have internal structures similar to that of terrestrial planets. Terrestrial planets can have surface structures such as canyons, craters, mountains, volcanoes, and others, depending on the presence of an erosive liquid and / or tectonic activity. Terrestrial planets have "secondary atmospheres", generated by volcanic out-gassing or from comet impact debris. This contrasts with the outer, giant planets, whose atmospheres are "primary"; primary atmospheres were captured directly from the original solar nebula.
Terrestrial planet | Structure
Despite that, the compositions for the planets are well-constrained. WASP-47e has almost no volatile materials (water, hydrogen/helium), d has a thin gaseous envelope, and b and c are both gas giants like Jupiter and Saturn. The presence of two rather small planets, as well as the orbital configuration of the first three planets, is not expected for Hot Jupiter systems, as a migrating gas giant is thought to kick out any small inner planets. In order for the system to come out the way it is now, the two gas giants likely would have to have formed before the lower-mass planets e and d.
WASP-47 | Planetary system
After planets, circumstellar disks are one of the most commonly observed properties of planetary systems, particularly of young stars. The Solar System possesses at least four major circumstellar disks (the asteroid belt, Kuiper belt, scattered disc, and Oort cloud) and clearly observable disks have been detected around nearby solar analogs including Epsilon Eridani and Tau Ceti. Based on observations of numerous similar disks, they are assumed to be quite common attributes of stars on the main sequence. Interplanetary dust clouds have been studied in the Solar System and analogs are believed to be present in other planetary systems. Exozodiacal dust, an exoplanetary analog of zodiacal dust, the 1–100 micrometre-sized grains of amorphous carbon and silicate dust that fill the plane of the Solar System has been detected around the 51 Ophiuchi, Fomalhaut, Tau Ceti, and Vega systems.
Planetary system | Circumstellar disks and dust structures
Although their exteriors are subjected to intense solar radiation that can alter their chemistry, their interiors contain pristine material essentially untouched since the planetesimal was formed. This makes each planetesimal a 'time capsule', and their composition might reveal the conditions in the Solar Nebula from which our planetary system was formed. The most primitive planetesimals visited by spacecraft are the contact binary Arrokoth.
Planetesimal | Planetesimals in the Solar System
The vast majority of the Solar System consists of a near-vacuum known as the interplanetary medium. Along with light, the Sun radiates a continuous stream of charged particles (a plasma) known as the solar wind. This stream of particles spreads outwards at roughly 1.5 million kilometres per hour, creating a tenuous atmosphere that permeates the interplanetary medium out to at least 100 AU "(see )". Activity on the Sun's surface, such as solar flares and coronal mass ejections, disturbs the heliosphere, creating space weather and causing geomagnetic storms. The largest structure within the heliosphere is the heliospheric current sheet, a spiral form created by the actions of the Sun's rotating magnetic field on the interplanetary medium.
Solar System | Interplanetary medium
In December 2004, it was found to have a long-period 1.78 M giant planet in orbit around it.
HD 89307 | Planetary system
Jupiter was expected to either consist of a dense core, a surrounding layer of liquid metallic hydrogen (with some helium) extending outward to about 78% of the radius of the planet, and an outer atmosphere consisting predominantly of molecular hydrogen, or perhaps to have no core at all, consisting instead of denser and denser fluid (predominantly molecular and metallic hydrogen) all the way to the center, depending on whether the planet accreted first as a solid body or collapsed directly from the gaseous protoplanetary disk. However, the "Juno" mission, which arrived in July 2016, found that Jupiter has a very diffuse core, mixed into the mantle.
Jupiter | Internal structure
Kepler-78 planetary system is composed by one planet called Kepler-78b, a planet slightly bigger than Earth with an extremely close orbit to the parent star. The orbital period of this planet is about 8.5 hours because of its proximity to its star. While it has a similar density to the Earth (at 5.57 g/cm, its surface temperature is about 1300 to 1500 K.
Kepler-78 | Planetary system
The Sun is a star located at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma and magnetic fields. It has a diameter of about , around 109 times that of Earth, and its mass (1.989 kilograms, approximately 330,000 times that of Earth) accounts for some 99.86% of the total mass of the Solar System. Chemically, about three quarters of the Sun's mass consists of hydrogen, while the rest is mostly helium. The remaining 1.69% (equal to 5,600 times the mass of Earth) consists of heavier elements, including oxygen, carbon, neon and iron.
Solar phenomena | Sun
With a density of 0.82 g/cm, assuming that the primary and satellite have the same density, is one of the largest known solid objects in the Solar System that is less dense than water. Why this should be is not well understood, because objects of its size in the Kuiper belt often contain a fair amount of rock and are hence pretty dense. To have a similar composition to others large KBOs, it would have to be exceptionally porous, which was believed to be unlikely given the compactability of water ice; this low density thus astonished astronomers. Studies by Grundy et al.
(55637) 2002 UX25 | Composition
Unlike planets, these objects basically appear to move in straight lines, so for normal use no complicated calculation is needed to find their mean position.
Apparent place | Solar System objects
The Solar System formed 4.568 billion years ago from the gravitational collapse of a region within a large molecular cloud. This initial cloud was likely several light-years across and probably birthed several stars. As is typical of molecular clouds, this one consisted mostly of hydrogen, with some helium, and small amounts of heavier elements fused by previous generations of stars. As the region that would become the Solar System, known as the pre-solar nebula, collapsed, conservation of angular momentum caused it to rotate faster. The centre, where most of the mass collected, became increasingly hotter than the surrounding disc. As the contracting nebula rotated faster, it began to flatten into a protoplanetary disc with a diameter of roughly 200 AU and a hot, dense protostar at the centre.
Solar System | Formation and evolution
Mars (1.5 AU from the Sun) is smaller than Earth and Venus (). It has an atmosphere of mostly carbon dioxide with a surface pressure of 6.1 millibars (roughly 0.6% of that of Earth). Its surface, peppered with vast volcanoes, such as Olympus Mons, and rift valleys, such as Valles Marineris, shows geological activity that may have persisted until as recently as 2 million years ago. Its red colour comes from iron oxide (rust) in its soil. Mars has two tiny natural satellites (Deimos and Phobos) thought to be either captured asteroids, or ejected debris from a massive impact early in Mars's history.
Solar System | Mars
All terrestrial planets (and some satellites, such as the Moon) are essentially composed of silicates wrapped around iron cores. The large outer Solar System moons and Pluto have more ice, and less rock and metal, but still undergo analogous processes.
Comparative planetary science | Geology and geochemistry
The giant planets (Jupiter, Saturn, Uranus, and Neptune) formed further out, beyond the frost line, the point between the orbits of Mars and Jupiter where material is cool enough for volatile icy compounds to remain solid. The ices that formed these planets were more plentiful than the metals and silicates that formed the terrestrial inner planets, allowing them to grow massive enough to capture large atmospheres of hydrogen and helium, the lightest and most abundant elements. Leftover debris that never became planets congregated in regions such as the asteroid belt, Kuiper belt, and Oort cloud. The Nice model is an explanation for the creation of these regions and how the outer planets could have formed in different positions and migrated to their current orbits through various gravitational interactions.
Solar System | Formation and evolution
The Solar System orbits within the Milky Way, a barred spiral galaxy that is a prominent member of the Local Group of galaxies. It is a rotating mass of gas, dust, stars and other objects, held together by mutual gravitational attraction. As the Earth is located within the dusty outer arms, there are large portions of the Milky Way that are obscured from view. In the center of the Milky Way is the core, a bar-shaped bulge with what is believed to be a supermassive black hole at its center. This is surrounded by four primary arms that spiral from the core.
Astronomy | Galactic astronomy
The outer region of the Solar System is home to the giant planets and their large moons. The centaurs and many short-period comets also orbit in this region. Due to their greater distance from the Sun, the solid objects in the outer Solar System contain a higher proportion of volatiles, such as water, ammonia, and methane than those of the inner Solar System because the lower temperatures allow these compounds to remain solid.
Solar System | Outer Solar System
The game takes place in a borderless and randomly generated universe, filled with asteroids, planets, stars and planetary systems. Life forms are also present in the game. They appear on planets sufficiently big to store life, and are represented by a variety of ships of different size and attack power. Spaceships are coloured green if they belong to the player's planet, or to a planet that belongs to the player's planetary system; red if they belong to an enemy planet or planetary system; and white if they don't belong to any planet or system. All the spaceships in the map are controlled by the game's artificial intelligence (AI), and they will constantly engage in combat against enemy ships, asteroids or planets to destroy them.
Solar 2 | Gameplay
The mass would be 11% solar mass (). All components in the star system including Star A are smaller, cooler and less massive, luminous, and metallic than the Sun and 51 Pegasi. An infrared excess has been detected around the primary, most likely indicating the presence of a circumstellar disk at a radius of more than 97 AU. The temperature of this dust is below 25 K.
85 Pegasi | Introduction
By 3.5 billion years from now, Earth's surface conditions will be similar to those of Venus today. Around 5.4 billion years from now, the core of the Sun will become hot enough to trigger hydrogen fusion in its surrounding shell. This will cause the outer layers of the star to expand greatly, and the star will enter a phase of its life in which it is called a red giant. Within 7.5 billion years, the Sun will have expanded to a radius of 1.2 AU—256 times its current size. At the tip of the red giant branch, as a result of the vastly increased surface area, the Sun's surface will be much cooler (about 2600 K) than now and its luminosity much higher—up to 2,700 current solar luminosities.
Formation and evolution of the Solar System | The Sun and planetary environments
The Kuiper belt is a great ring of debris similar to the asteroid belt, but consisting mainly of objects composed primarily of ice. It extends between 30 and 50 AU from the Sun. Though it is estimated to contain anything from dozens to thousands of dwarf planets, it is composed mainly of small Solar System bodies. Many of the larger Kuiper belt objects, such as Quaoar, Varuna, and Orcus, may prove to be dwarf planets with further data. There are estimated to be over 100,000 Kuiper belt objects with a diameter greater than 50 km, but the total mass of the Kuiper belt is thought to be only a tenth or even a hundredth the mass of Earth.
Solar System | Kuiper belt
Additionally, a much longer wavelength suggests the existence of a much wider belt of material, analogous to the Kuiper belt. The hierarchy of this system is somewhat reminiscent of that of Epsilon Eridani, without an inner asteroid belt.
HD 10647 | Planetary system
Travis Barman at Lowell Observatory in Flagstaff, Arizona analyzed the emission spectrum of this planet, and believes that its atmosphere contains water, although previous research suggests that the atmosphere is composed mostly of silicate clouds.
HD 209458 | Planetary system
The OGLE-2003-BLG-235L/MOA-2003-BLG-53L system consists of one planet as determined by the discovery team and the follow-up confirmation observations.
OGLE-2003-BLG-235/MOA-2003-BLG-53 | Planetary system
A planet of high density is inferred to be rocky, like Earth and the other terrestrial planets of the Solar System.
Exoplanetology | Radius, density, and bulk composition
Planetary systems come from protoplanetary disks that form around stars as part of the process of star formation. During formation of a system much material is gravitationally scattered into far-flung orbits and some planets are ejected completely from the system becoming rogue planets.
Planetary system | Origin and evolution
The structures of the giant planets and their moons are also examined, as is the make-up of the minor bodies of the Solar System, such as asteroids, the Kuiper Belt, and comets.
Planetary geology | Introduction
Assuming a circular projected shape for the components' occultation profiles, the diameters of the primary and secondary are estimated to be and , respectively. The diameter ratio of the secondary to the primary is 0.76:1.00—the secondary component is approximately 75% as large as the primary. Since the mutual orbit of the components is undetermined, the mass and density of the system cannot be derived. The individual components of the system are among the smallest trans-Neptunian objects with sizes measured with stellar occultations, following the sednoid 541132 Leleākūhonua (~) and the Kuiper belt object 486958 Arrokoth (~). Given the components' estimated diameters and their combined absolute magnitude of 7.2, their calculated geometric albedos indicate that they have dark surfaces, reflecting about 5% of incident visible light.
(523764) 2014 WC510 | Physical characteristics
Gradually, the hydrogen burning in the shell around the solar core will increase the mass of the core until it reaches about 45% of the present solar mass. At this point the density and temperature will become so high that the fusion of helium into carbon will begin, leading to a helium flash; the Sun will shrink from around 250 to 11 times its present (main-sequence) radius. Consequently, its luminosity will decrease from around 3,000 to 54 times its current level, and its surface temperature will increase to about 4770 K. The Sun will become a horizontal giant, burning helium in its core in a stable fashion much like it burns hydrogen today.
Formation and evolution of the Solar System | The Sun and planetary environments
In 2009, two gas giant planets were found in orbit around the star.
BD−08°2823 | Planetary system
Jupiter is composed primarily of gaseous and liquid matter. It is the largest planet in the Solar System, with a diameter of at its equator. The average density of Jupiter, 1.326 g/cm, is the second highest of the giant planets, but lower than those of the four terrestrial planets.
Jupiter | Physical characteristics
With a minimum mass of around 4.5 Earths, it is a small Super-Earth.
Gliese 676 | Planetary system
The planet has a Mass of and a bulk density of g/cm, which is an earth-like density. The planet has likely a rocky core and a substantial atmospheric layer, composed of volatiles. The K2-138 system is unique for being the first exoplanet system discovered entirely by citizen scientists.
K2-138b | Introduction
' has a very reddish color (RR), indicative of a non-carbonaceous composition rich in tholins and methane. According to the "Johnston's archive", the object only measures 93 kilometers in diameter based on an absolute magnitude of 8.4, and an assumed albedo of 0.09 for the body's surface. Since it is far too small for being considered a dwarf planet candidate, it is not listed at Michael Brown website. As of 2018, no rotational lightcurve of ' has been obtained from photometric observations. The body's rotation period, pole and shape remain unknown.
1999 TR11 | Physical characteristics
The table below lists Solar System bodies once considered to be planets.
Planet | Objects formerly considered "planets"
The planetary core consists of the innermost layer(s) of a planet. Cores of specific planets may be entirely solid or entirely liquid, or may be a mixture of solid and liquid layers as is the case in the Earth. In the Solar System, core size can range from about 20% (Moon) to 85% of a planet's radius (Mercury). Gas giants also have cores, though the composition of these are still a matter of debate and range in possible composition from traditional stony/iron, to ice or to fluid metallic hydrogen. Gas giant cores are proportionally much smaller than those of terrestrial planets, though theirs can be considerably larger than the Earth's nevertheless; Jupiter has one 10–30 times heavier than Earth, and exoplanet HD149026 b may have a core 100 times the mass of the Earth.
Planetary core | Introduction
The single known planet orbiting this star was identified as a candidate based on photometry from the first four months of data from the Kepler spacecraft. Confirmation was obtained in 2012 after extensive follow-up observations and analysis of the Kepler light curves. The calculated density of the planet is approximately 6.4 g cm, similar to earth's 5.5 g cm, which suggests a rocky composition. With an equilibrium temperature of 2025 Kelvin, the top few-hundred kilometers of the planet is probably molten.
HD 179070 | Planetary system
When excluding the Sun, the four giant planets account for more than 99% of the mass of the Solar System.
List of gravitationally rounded objects of the Solar System | Planets
The inner Solar System also contains near-Earth asteroids, many of which cross the orbits of the inner planets. Some of them are potentially hazardous objects.
Solar System | Asteroid groups
The four outer planets, or giant planets (sometimes called Jovian planets), collectively make up 99% of the mass known to orbit the Sun. Jupiter and Saturn are together more than 400 times the mass of Earth and consist overwhelmingly of hydrogen and helium. Uranus and Neptune are far less massiveless than 20 Earth masses () eachand are composed primarily of ices. For these reasons, some astronomers suggest they belong in their own category, ice giants. All four giant planets have rings, although only Saturn's ring system is easily observed from Earth. The term "superior planet" designates planets outside Earth's orbit and thus includes both the outer planets and Mars.
Solar System | Outer planets
This is a partial list of Solar System objects by size, arranged in descending order of mean volumetric radius, and divided into several size classes. These lists can also be sorted according to an object's mass and, for the largest objects, volume, density and surface gravity, insofar as these values are available. This list contains the Sun, the planets, dwarf planets, many of the larger small Solar System bodies (which includes the asteroids), all named natural satellites, and a number of smaller objects of historical or scientific interest, such as comets and near-Earth objects. Objects on this list are ordered by mean radius rather than mass; thus, objects on the lower portions of the table can be more massive than objects higher on the list if they have a higher density.
List of Solar System objects by size | Introduction
The Sun has eight known planets. This includes four terrestrial planets (Mercury, Venus, Earth, and Mars), two gas giants (Jupiter and Saturn), and two ice giants (Uranus and Neptune). The Solar System also has at least five dwarf planets, an asteroid belt, numerous comets, and a large number of icy bodies which lie beyond the orbit of Neptune.
Sun | Planetary system
Based upon radial velocity variations of HD 132563B, the presence of an ordinary giant planet has been inferred by S. Desidera "et al." (2011). This object is orbiting the star with a period of 1,544 days, at a distance of about 2.6 AU, and with an orbital eccentricity of 0.22.
HD 132563 | Planetary system
The existence of this planet around a 1.68 solar mass () star provides evidence for the existence of planetary systems around A-type main sequence stars.
HD 192699 b | Introduction
It is not presently clear whether a lower size bound will be established as part of the definition of small Solar System bodies in the future, or if it will encompass all material down to the level of meteoroids, the smallest macroscopic bodies in orbit around the Sun. (On a microscopic level there are even smaller objects such as interplanetary dust, particles of solar wind and free particles of hydrogen.) Except for the largest, which are in hydrostatic equilibrium, natural satellites (moons) differ from small Solar System bodies not in size, but in their orbits. The orbits of natural satellites are not centered on the Sun, but around other Solar System objects such as planets, dwarf planets, and small Solar System bodies.
Small Solar System body | Definition
Every planet began its existence in an entirely fluid state; in early formation, the denser, heavier materials sank to the centre, leaving the lighter materials near the surface. Each therefore has a differentiated interior consisting of a dense planetary core surrounded by a mantle that either is or was a fluid. The terrestrial planets are sealed within hard crusts, but in the giant planets the mantle simply blends into the upper cloud layers. The terrestrial planets have cores of elements such as iron and nickel, and mantles of silicates. Jupiter and Saturn are believed to have cores of rock and metal surrounded by mantles of metallic hydrogen.
Planet | Internal differentiation
has a diameter estimated between 117 and 125 kilometers, roughly a quarter the size of ("Buffy"), which is estimated at around , roughly a quarter the size of Pluto. It is therefore not a dwarf planet candidate.
2015 FJ345 | Physical characteristics
In 2009, a gas giant was found in orbit around the star using the radial velocity method. It has an orbital period of and has at least 68% of the mass of Jupiter.
HD 8535 | Planetary system
Some SSSBs are just collections of relatively small rocks that are weakly held next to each other by gravity but are not actually fused into a single big bedrock. Some larger SSSBs are nearly round but have not reached hydrostatic equilibrium. The small Solar System body 4 Vesta is large enough to have undergone at least partial planetary differentiation. Stars like the Sun are also spheroidal due to gravity's effects on their plasma, which is a free-flowing fluid. Ongoing stellar fusion is a much greater source of heat for stars compared to the initial heat released during formation.
Spherical Earth | Shapes of other bodies
The giant planet is Neptune-sized, about 20-55 Earth-masses (). It has a radius 6.2 times that of Earth's. The star system is 7200 light years from Earth. The planet orbits a close binary, with a more distant binary orbiting at a distance, forming the quadruple star system. The star system has the Kepler Input Catalogue name KIC 4862625 as well as the designation Kepler-64. The close binary (Aa+Ab) that the planet circles has an orbital period of 20 days. They form an eclipsing binary pair. The two stars are (Aa) 1.384 solar mass () F-type main-sequence star and (Ab) red dwarf.
PH1b | Star system
More commonly, systems consisting of multiple Super-Earths have been detected.
Planetary system | System architectures
Being distant from the Sun and major planets, Kuiper belt objects are thought to be relatively unaffected by the processes that have shaped and altered other Solar System objects; thus, determining their composition would provide substantial information on the makeup of the earliest Solar System. Due to their small size and extreme distance from Earth, the chemical makeup of KBOs is very difficult to determine. The principal method by which astronomers determine the composition of a celestial object is spectroscopy. When an object's light is broken into its component colors, an image akin to a rainbow is formed. This image is called a spectrum.
Kuiper belt | Composition
This list contains a selection of objects 50 and 99 km in radius (100 km to 199 km in average diameter). The listed objects currently include most objects in the asteroid belt and moons of the giant planets in this size range, but many newly discovered objects in the outer Solar System are missing, such as those included in the following reference. Asteroid spectral types are mostly Tholen, but some might be SMASS.
List of Solar System objects by size | From 50 to 99 km
Based upon blackbody models, it is orbiting from the host star with a mean temperature of 280 K. There may be an additional, 60 K debris disk orbiting at a distance of .
HD 45184 | Planetary system
This is a directory of lists of geological features on planets excepting Earth, moons and asteroids ordered by increasing distance from the Sun.
Lists of geological features of the Solar System | Introduction
Mike Brown, the discoverer of Sedna and Eris, has said that at least 53 known bodies in the Solar System probably fit the definition, and that a complete survey would probably reveal more than 200. The definition would have considered a pair of objects to be a double planet system if each component independently satisfied the planetary criteria and the common center of gravity of the system (known as the "barycenter") was located outside of both bodies. Pluto and Charon would have been the only known double planet in the Solar System. Other planetary satellites (like Earth and its moon) might be in hydrostatic equilibrium, but would still not have been defined as a component of a double planet, since the barycenter of the system lies within the more massive celestial body (the Earth).
IAU definition of planet | First draft proposal
Jupiter (5.2 AU), at , is 2.5 times the mass of all the other planets put together. It is composed largely of hydrogen and helium. Jupiter's strong internal heat creates semi-permanent features in its atmosphere, such as cloud bands and the Great Red Spot. Jupiter has 79 known satellites. The four largest, Ganymede, Callisto, Io, and Europa, show similarities to the terrestrial planets, such as volcanism and internal heating. Ganymede, the largest satellite in the Solar System, is larger than Mercury.
Solar System | Jupiter
Scattered objects, like other trans-Neptunian objects, have low densities and are composed largely of frozen volatiles such as water and methane. Spectral analysis of selected Kuiper belt and scattered objects has revealed signatures of similar compounds. Both Pluto and Eris, for instance, show signatures for methane. Astronomers originally supposed that the entire trans-Neptunian population would show a similar red surface colour, as they were thought to have originated in the same region and subjected to the same physical processes. Specifically, SDOs were expected to have large amounts of surface methane, chemically altered into complex organic molecules by energy from the Sun.
Scattered disc | Composition