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Epsilon Eridani
Epsilon Eridani ( Latinized from ε Eridani), proper name Ran, is a star in the southern constellation of Eridanus. At a declination of −9.46°, it is visible from most of Earth's surface. Located at a distance from the Sun, it has an apparent magnitude of 3.73, making it the third-closest individual star (or star system) visible to the naked eye. The star is estimated to be less than a billion years old. This relative youth gives Epsilon Eridani a higher level of magnetic activity than the Sun, with a stellar wind 30 times as strong. The star's rotation period is 11.2 days at the equator. Epsilon Eridani is smaller and less massive than the Sun, and has a lower level of elements heavier than helium. It is a main-sequence star of spectral class K2, with an effective temperature of about , giving it an orange hue. It is a candidate member of the Ursa Major moving group of stars, which share a similar motion through the Milky Way, implying these stars shared a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
J2000
In astronomy, an epoch or reference epoch is a moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a celestial body, as they are subject to perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or aphelion of its orbit, or the size of the major axis of its orbit. The main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities. The applied tools of the disciplines of celestial mechanics or its subfield orbital mechanics (for predicting orbital paths and positions for bodies in motion under the gravitational effects of other bodies) can be used to generate an ephemeris, a table of values giving ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectral Class
In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with spectral lines. Each line indicates a particular chemical element or molecule, with the line strength indicating the abundance of that element. The strengths of the different spectral lines vary mainly due to the temperature of the photosphere, although in some cases there are true abundance differences. The ''spectral class'' of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere's temperature. Most stars are currently classified under the Morgan–Keenan (MK) system using the letters ''O'', ''B'', ''A'', ''F'', ''G'', ''K'', and ''M'', a sequence from the hottest (''O'' type) to the coolest (''M'' type). Each letter class is then subdivided ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Analog
Solar-type stars, solar analogs (also analogues), and solar twins are stars that are particularly similar to the Sun. The stellar classification is a hierarchy with solar twin being most like the Sun followed by solar analog and then solar-type. Observations of these stars are important for understanding better the properties of the Sun in relation to other stars and the habitability of planets. By similarity to the Sun Defining the three categories by their similarity to the Sun reflects the evolution of astronomical observational techniques. Originally, solar-type was the closest that similarity to the Sun could be defined. Later, more precise measurement techniques and improved observatories allowed for greater precision of key details like temperature, enabling the creation of a solar analog category for stars that were particularly similar to the Sun. Later still, continued improvements in precision allowed for the creation of a solar-twin category for near-perfect matches ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kuiper Belt
The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times as wide and 20–200 times as massive. Like the asteroid belt, it consists mainly of small Solar System body, small bodies or remnants from when the Formation and evolution of the Solar System, Solar System formed. While many asteroids are composed primarily of rock (geology), rock and metal, most Kuiper belt objects are composed largely of frozen Volatile (astrogeology), volatiles (termed "ices"), such as methane, ammonia, and water. The Kuiper belt is home to most of the objects that astronomers generally accept as dwarf planets: 90482 Orcus, Orcus, Pluto, Haumea, 50000 Quaoar, Quaoar, and Makemake. Some of the Solar System's natural satellite, moons, such as Neptune's Triton (moon), Triton and Saturn's Phoebe (moon), Phoebe, may ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Debris Disc
Debris (, ) is rubble, wreckage, ruins, litter and discarded garbage/refuse/trash, scattered remains of something destroyed, or, as in geology, large rock fragments left by a melting glacier, etc. Depending on context, ''debris'' can refer to a number of different things. The first apparent use of the French word in English is in a 1701 description of the army of Prince Rupert upon its retreat from a battle with the army of Oliver Cromwell, in England. Disaster In disaster scenarios, tornadoes leave behind large pieces of houses and mass destruction overall. This debris also flies around the tornado itself when it is in progress. The tornado's winds capture debris it kicks up in its wind orbit, and spins it inside its vortex. The tornado's wind radius is larger than the funnel itself. Tsunamis and hurricanes also bring large amounts of debris, such as Hurricane Katrina in 2005 and Hurricane Sandy in 2012. Earthquakes rock cities to rubble debris. Geological In geology, debris ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planetary System
A planetary system is a set of gravity, gravitationally bound non-stellar Astronomical object, bodies 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. For example, the Sun together with the planetary system revolving around it, including Earth, form the Solar System. The term exoplanetary system is sometimes used in reference to other planetary systems. Planetary systems are, by convention, named for their host, or parent star, as is the case in our Solar Planetary System, named for its hosting, star, "Sol". Debris disk, Debris disks are known to be common while other objects are more difficult to observe. Of particular interest to astrobiology is the habitable zone of planetary systems where planets could have surface liquid water, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Proper Names Of Exoplanets
Proper names for planets outside of the Solar System – known as exoplanets – are chosen by the International Astronomical Union (IAU) through public naming contests known as NameExoWorlds. Naming The IAU's names for exoplanets – and on most occasions their Planet-hosting stars, host stars – are chosen by the Executive Committee Working Group (ECWG) on Public Naming of Planets and Planetary Satellites, a group working parallel with the IAU Working Group on Star Names, Working Group on Star Names (WGSN). List of proper names of stars, Proper names of stars chosen by the ECWG are explicitly recognised by the WGSN. The ECWG's rules for naming exoplanets are identical to those adopted by the Minor Planet Center for minor planets. Names are a single word consisting of sixteen characters or less, pronounceable in some language, Profanity, non-offensive, and not identical to existing proper names of astronomical objects. Copyrighted names, names of living individuals, and name ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epsilon Eridani B
Epsilon Eridani b, formally named AEgir , is an exoplanet approximately 10.5 light-years away orbiting the star Epsilon Eridani, in the constellation of Eridanus (constellation), Eridanus (the River). The planet was discovered in 2000, and as of 2024 remains the only confirmed planet in its planetary system. It is a remarkably close analog to Jupiter, with similar mass and orbit. Name The planet and its host star are one of the planetary systems selected by the International Astronomical Union as part of NameExoWorlds, their public process for giving proper names to exoplanets and their host star (where no proper name already exists). The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning names were AEgir for the planet (pronounced [Anglicized] or , an approximation of the old Norse Ægir) and Ran for the star. James Ott, age 14, submitted the names for the IAU contest and won. The moon Aegir (moon), Aegir of Saturn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giant Planet
A giant planet, sometimes referred to as a jovian planet (''Jove'' being another name for the Roman god Jupiter (mythology), Jupiter), is a diverse type of planet much larger than Earth. Giant planets are usually primarily composed of low-boiling point materials (volatile (astrogeology), volatiles), rather than rock (geology), rock or other solid matter, but massive solid planets can also exist. There are four such planets in the Solar System: Jupiter, Saturn, Uranus, and Neptune. Many exoplanet, extrasolar giant planets have been identified. Giant planets are sometimes known as gas giants, but many astronomers now apply the term only to Jupiter and Saturn, classifying Uranus and Neptune, which have different compositions, as ice giants. Both names are potentially misleading; the Solar System's giant planets all consist primarily of fluids above their critical point (thermodynamics), critical points, where distinct gas and liquid phases do not exist. Jupiter and Saturn are princip ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methods Of Detecting Extrasolar Planets
Methods of detecting exoplanets usually rely on indirect strategies – that is, they do not directly image the planet but deduce its existence from another signal. Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty of detecting such a faint light source, the glare from the parent star washes it out. For those reasons, very few of the exoplanets reported have been detected directly, with even fewer being resolved from their host star. Established detection methods The following methods have proven successful at least once for discovering a new planet or detecting an already discovered planet: Radial velocity A star with a planet will move in its own small orbit in response to the planet's gravity. This leads to variations in the speed with which the star moves toward or away from Ea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radial Velocity
The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity onto the relative direction or line-of-sight (LOS) connecting the two points. The radial speed or range rate is the temporal rate of the distance or range between the two points. It is a signed scalar quantity, formulated as the scalar projection of the relative velocity vector onto the LOS direction. Equivalently, radial speed equals the norm of the radial velocity, modulo the sign. In astronomy, the point is usually taken to be the observer on Earth, so the radial velocity then denotes the speed with which the object moves away from the Earth (or approaches it, for a negative radial velocity). Formulation Given a differentiable vector \mathbf r \in \mathbb^3 defining the instantaneous relative position of a target with respe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Open Cluster
An open cluster is a type of star cluster made of tens to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and many more are thought to exist. Each one is loosely bound by mutual gravity, gravitational attraction and becomes disrupted by close encounters with other clusters and clouds of gas as they orbit the Galactic Center. This can result in a loss of cluster members through internal close encounters and a dispersion into the main body of the galaxy. Open clusters generally survive for a few hundred million years, with the most massive ones surviving for a few billion years. In contrast, the more massive globular clusters of stars exert a stronger gravitational attraction on their members, and can survive for longer. Open clusters have been found only in spiral galaxy, spiral and irregular galaxy, irregular galaxies, in which active star formatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
