|
HD 41248
HD 41248 is a star in the constellation Pictor. It is a star very similar to the Sun, with the same spectral type (G2V). It has 68% of the Sun's luminosity, 92% of its mass and 78% of its diameter. It is estimated to be around 2 billion years old, and it has a lower metallicity—43% that of the Sun. With an apparent visual magnitude of 8.81, it is too faint to be seen with the unaided eye, and is located around 170 light-years (52 parsecs) away from the Solar System. HD 41248 was investigated in the High Accuracy Radial Velocity Planet Searcher The High Accuracy Radial Velocity Planet Searcher (HARPS) is a high-precision echelle planet-finding spectrograph installed in 2002 on the ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003. H ... (HARPS) and initially thought not to have planets, but review of its spectrum showed it to have two super-earths with orbital periods of 18.357 days and 25.648 days and minimum masse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
J2000
In astronomy, an epoch or reference epoch is a instant, 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 Astronomical object, celestial body, as they are subject to Perturbation (astronomy), 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 Perihelion and aphelion, 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 bodi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High Accuracy Radial Velocity Planet Searcher
The High Accuracy Radial Velocity Planet Searcher (HARPS) is a high-precision echelle planet-finding spectrograph installed in 2002 on the ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003. HARPS has discovered over 130 exoplanets to date, with the first one in 2004, making it the most successful planet finder behind the Kepler space observatory. It is a second-generation radial-velocity spectrograph, based on experience with the ELODIE and CORALIE instruments. Characteristics The HARPS can attain a precision of 0.97 m/s (3.5 km/h), making it one of only two instruments worldwide with such accuracy. This is due to a design in which the target star and a reference spectrum from a thorium lamp are observed simultaneously using two identical optic fibre feeds, and to careful attention to mechanical stability: the instrument sits in a vacuum vessel which is temperature-controlled to within 0.01 kelvins. The precision ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henry Draper Catalogue Objects
Henry may refer to: People *Henry (given name) *Henry (surname) * Henry Lau, Canadian singer and musician who performs under the mononym Henry Royalty * Portuguese royalty ** King-Cardinal Henry, King of Portugal ** Henry, Count of Portugal, Henry of Burgundy, Count of Portugal (father of Portugal's first king) ** Prince Henry the Navigator, Infante of Portugal ** Infante Henrique, Duke of Coimbra (born 1949), the sixth in line to Portuguese throne * King of Germany ** Henry the Fowler (876–936), first king of Germany * King of Scots (in name, at least) ** Henry Stuart, Lord Darnley (1545/6–1567), consort of Mary, queen of Scots ** Henry Benedict Stuart, the 'Cardinal Duke of York', brother of Bonnie Prince Charlie, who was hailed by Jacobites as Henry IX * Four kings of Castile: **Henry I of Castile **Henry II of Castile **Henry III of Castile **Henry IV of Castile * Five kings of France, spelt ''Henri'' in Modern French since the Renaissance to italianize the name and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
G-type Main-sequence Stars
A G-type main-sequence star (Spectral type: G-V), also often, and imprecisely called a yellow dwarf, or G star, is a main-sequence star (luminosity class V) of spectral type G. Such a star has about 0.9 to 1.1 solar masses and an effective temperature between about 5,300 and 6,000 K. Like other main-sequence stars, a G-type main-sequence star is converting the element hydrogen to helium in its core by means of nuclear fusion, but can also fuse helium when hydrogen runs out. The Sun, the star in the center of the Solar System to which the Earth is gravitationally bound, is an example of a G-type main-sequence star (G2V type). Each second, the Sun fuses approximately 600 million tons of hydrogen into helium in a process known as the proton–proton chain (4 hydrogens form 1 helium), converting about 4 million tons of matter to energy. Besides the Sun, other well-known examples of G-type main-sequence stars include Alpha Centauri, Tau Ceti, Capella and 51 Pegasi. The term ''yello ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pictor (constellation)
Pictor is a constellation in the Southern Celestial Hemisphere, located between the star Canopus and the Large Magellanic Cloud. Its name is Latin for painter, and is an abbreviation of the older name Equuleus Pictoris (the "painter's easel"). Normally represented as an easel, Pictor was named by Abbé Nicolas-Louis de Lacaille in the 18th century. The constellation's brightest star is Alpha Pictoris, a white main-sequence star around 97 light-years away from Earth. Pictor also hosts RR Pictoris, a cataclysmic variable star system that flared up as a nova, reaching apparent (visual) magnitude 1.2 in 1925 before fading into obscurity. Pictor has attracted attention because of its second-brightest star Beta Pictoris, 63.4 light-years distant from Earth, which is surrounded by an unusual dust disk rich in carbon, as well as an exoplanet (extrasolar planet). Another five stars in the constellation have been observed to have planets. Among them is HD 40307, an ora ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around 1 millimeter (300 GHz) to the nominal red edge of the visible spectrum, around 700 nanometers (430 THz). Longer IR wavelengths (30 μm-100 μm) are sometimes included as part of the terahertz radiation range. Almost all black-body radiation from objects near room temperature is at infrared wavelengths. As a form of electromagnetic radiation, IR propagates energy and momentum, exerts radiation pressure, and has properties corresponding to both those of a wave and of a particle, the photon. It was long known that fires emit invisible heat; in 1681 the pioneering experimenter Edme Mariotte showed that glass, though transparent to sunlight, obstructed radiant heat. In 1800 the astronomer Sir William Herschel discovered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Resonance
In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relationship is found between a pair of objects (binary resonance). The physical principle behind orbital resonance is similar in concept to pushing a child on a swing, whereby the orbit and the swing both have a natural frequency, and the body doing the "pushing" will act in periodic repetition to have a cumulative effect on the motion. Orbital resonances greatly enhance the mutual gravitational influence of the bodies (i.e., their ability to alter or constrain each other's orbits). In most cases, this results in an ''unstable'' interaction, in which the bodies exchange momentum and shift orbits until the resonance no longer exists. Under some circumstances, a resonant system can be self-correcting and thus stable. Examples are the 1:2:4 resonance ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Super-Earth
A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively. The term "super-Earth" refers only to the mass of the planet, and so does not imply anything about the surface conditions or habitability. The alternative term "gas dwarfs" may be more accurate for those at the higher end of the mass scale, although "mini-Neptunes" is a more common term. Definition In general, super-Earths are defined by their masses, and the term does not imply temperatures, compositions, orbital properties, habitability, or environments. While sources generally agree on an upper bound of 10 Earth masses (~69% of the mass of Uranus, which is the Solar System's giant planet with the least mass), the lower bound varies from 1 or 1.9 to 5, with various other definitions appearing in the popular media. The term "super-Earth" is also used by astronomers to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar System" and "solar system" structures in theinaming guidelines document. The name is commonly rendered in lower case ('solar system'), as, for example, in the ''Oxford English Dictionary'' an''Merriam-Webster's 11th Collegiate Dictionary''. is the gravity, gravitationally bound system of the Sun and the objects that orbit it. It Formation and evolution of the Solar System, formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The solar mass, vast majority (99.86%) of the system's mass is in the Sun, with most of the Jupiter mass, remaining mass contained in the planet Jupiter. The four inner Solar System, inner system planets—Mercury (planet), Mercury, Venus, Earth and Mars—are terrest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Celestial Reference System
The International Celestial Reference System (ICRS) is the current standard celestial reference system adopted by the International Astronomical Union (IAU). Its origin is at the barycenter of the Solar System, with axes that are intended to "show no global rotation with respect to a set of distant extragalactic objects". This fixed reference system differs from previous reference systems, which had been based on Catalogues of Fundamental Stars that had published the positions of stars based on direct "observations of heir equatorial coordinates, right ascension and declination" and had adopted as "privileged axes ... the mean equator and the dynamical equinox" at a particular date and time. The International Celestial Reference Frame (ICRF) is a realization of the International Celestial Reference System using reference celestial sources observed at radio wavelengths. In the context of the ICRS, a reference ''frame'' (RF) is the physical realization of a reference ''system,'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sky & Telescope
''Sky & Telescope'' (''S&T'') is a monthly American magazine covering all aspects of amateur astronomy, including the following: *current events in astronomy and space exploration; *events in the amateur astronomy community; *reviews of astronomical equipment, books, and computer software; *amateur telescope making; and *astrophotography. The articles are intended for the informed lay reader and include detailed discussions of current discoveries, frequently by participating scientists. The magazine is illustrated in full color, with both amateur and professional photography of celestial sights, as well as tables and charts of upcoming celestial events. History ''Sky & Telescope'' was founded by Charles A Federer and his wife Helen Spence Federer and began publication at Harvard College Observatory in November 1941, as a result of the merger of the separate magazines, '' The Sky'' and '' The Telescope''. In 2005, Sky Publishing Corporation was acquired by New Track Media, a portfo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the earliest constellations likely go back to prehistory. People used them to relate stories of their beliefs, experiences, creation myth, creation, or mythology. Different cultures and countries adopted their own constellations, some of which lasted into the early 20th century before today's constellations were internationally recognized. The recognition of constellations has changed significantly over time. Many changed in size or shape. Some became popular, only to drop into obscurity. Some were limited to a single culture or nation. The 48 traditional Western constellations are Greek. They are given in Aratus' work ''Phenomena'' and Ptolemy's ''Almagest'', though their origin probably predates these works by several centuries. Constellation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
