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Mercury's Moon
Mercury is the closest planet to the Sun and lacks any natural satellites. An undiscovered moon orbiting the planet was hypothesized to exist in the early 1970s, but it turned out to be misinterpreted data from the star 31 Crateris. Observation of a moon of Mercury from Earth would be difficult because Mercury is relatively close to the Sun. For example, Mercury was not observed in the infrared spectrum until 1995. NASA's ''MESSENGER'' spacecraft, which orbited Mercury from 2011 to 2015, did not detect any moon. Mercury's small Hill sphere limits the potential for a natural satellite to exist. ''Mariner 10'' mission A moon of Mercury was for a short time thought to exist. On March 27, 1974, two days before ''Mariner 10'' made its flyby of Mercury, instruments began registering large amounts of ultraviolet radiation in the vicinity of Mercury that, according to one astronomer, "had no right to be there". [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mercury (planet)
Mercury is the smallest planet in the Solar System and the closest to the Sun. Its orbit around the Sun takes 87.97 Earth days, the shortest of all the Sun's planets. It is named after the Roman god ' ( Mercury), god of commerce, messenger of the gods, and mediator between gods and mortals, corresponding to the Greek god Hermes (). Like Venus, Mercury orbits the Sun within Earth's orbit as an inferior planet, and its apparent distance from the Sun as viewed from Earth never exceeds 28°. This proximity to the Sun means the planet can only be seen near the western horizon after sunset or the eastern horizon before sunrise, usually in twilight. At this time, it may appear as a bright star-like object, but is more difficult to observe than Venus. From Earth, the planet telescopically displays the complete range of phases, similar to Venus and the Moon, which recurs over its synodic period of approximately 116 days. The synodic proximity of Mercury to Earth makes Mercury most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypothetical Moons
A hypothetical Solar System object is a planet, natural satellite, subsatellite or similar body in the Solar System whose existence is not known, but has been inferred from observational scientific evidence. Over the years a number of hypothetical planets have been proposed, and many have been disproved. However, even today there is scientific speculation about the possibility of planets yet unknown that may exist beyond the range of our current knowledge. Planets * Counter-Earth, a planet situated on the other side of the Sun from that of the Earth. *Fifth planet (hypothetical), historical speculation about a planet between the orbits of Mars and Jupiter. ** Phaeton, a planet situated between the orbits of Mars and Jupiter whose destruction supposedly led to the formation of the asteroid belt. This hypothesis is now considered unlikely, since the asteroid belt has far too little mass to have resulted from the explosion of a large planet. In 2018, a study from researchers at th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypothetical Bodies Of The Solar System
A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous observations that cannot satisfactorily be explained with the available scientific theories. Even though the words "hypothesis" and "theory" are often used interchangeably, a scientific hypothesis is not the same as a scientific theory. A working hypothesis is a provisionally accepted hypothesis proposed for further research in a process beginning with an educated guess or thought. A different meaning of the term ''hypothesis'' is used in formal logic, to denote the antecedent of a proposition; thus in the proposition "If ''P'', then ''Q''", ''P'' denotes the hypothesis (or antecedent); ''Q'' can be called a consequent. ''P'' is the assumption in a (possibly counterfactual) ''What If'' question. The adjective ''hypothetical'', meaning "havin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Claimed Moons Of Earth
Claims of the existence of other moons of Earth—that is, of one or more natural satellites with relatively stable orbits of Earth, other than the Moon—have existed for some time. Several candidates have been proposed, but none have been confirmed. Since the 19th century, scientists have made genuine searches for more moons, but the possibility has also been the subject of a number of dubious non-scientific speculations as well as a number of likely hoaxes. Although the Moon is Earth's only natural satellite, there are a number of near-Earth objects (NEOs) with orbits that are in resonance with Earth. These have been called "second" moons of Earth or "minimoons". , an asteroid discovered on 27 April 2016, is possibly the most stable quasi-satellite of Earth. As it orbits the Sun, 469219 Kamoʻoalewa appears to circle around Earth as well. It is too distant to be a true satellite of Earth, but is the best and most stable example of a quasi-satellite, a type of near-Earth objec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypothetical Astronomical Object
Various unknown astronomical objects have been hypothesized throughout recorded history. For example, in the 5th century BCE, the philosopher Philolaus defined a hypothetical astronomical object which he called the " Central Fire", around which he proposed other celestial bodies (including the Sun) moved.Marco Ceccarelli, ''Distinguished Figures in Mechanism and Machine Science'' (2007), p. 124. Types of hypothetical astronomical objects Hypothetical astronomical objects have been speculated to exist both inside and outside of the Solar System, and speculation has included different kinds of stars, planets, and other astronomical objects. * For hypothetical astronomical objects in the Solar System, see: List of hypothetical Solar System objects * For hypothetical stars, see: Hypothetical star * For hypothetical brown dwarfs, see: List of brown dwarfs * For hypothetical black holes, see: Hypothetical black hole * For extrasolar moons, all of which are currently hypothetical, se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
243 Ida
Ida, minor planet designation 243 Ida, is an asteroid in the Koronis family of the asteroid belt. It was discovered on 29 September 1884 by Austrian astronomer Johann Palisa at Vienna Observatory and named after a nymph from Greek mythology. Later telescopic observations categorized Ida as an S-type asteroid, the most numerous type in the inner asteroid belt. On 28 August 1993, Ida was visited by the uncrewed ''Galileo'' spacecraft while en route to Jupiter. It was the second asteroid visited by a spacecraft and the first found to have a natural satellite. Ida's orbit lies between the planets Mars and Jupiter, like all main-belt asteroids. Its orbital period is 4.84 years, and its rotation period is 4.63 hours. Ida has an average diameter of . It is irregularly shaped and elongated, apparently composed of two large objects connected together. Its surface is one of the most heavily cratered in the Solar System, featuring a wide variety of crater sizes and ages. Ida's moon Dact ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caduceus
The caduceus (☤; ; la, cādūceus, from grc-gre, κηρύκειον "herald's wand, or staff") is the staff carried by Hermes in Greek mythology and consequently by Hermes Trismegistus in Greco-Egyptian mythology. The same staff was also borne by heralds in general, for example by Iris, the messenger of Hera. It is a short staff entwined by two serpents, sometimes surmounted by wings. In Roman iconography, it was often depicted being carried in the left hand of Mercury, the messenger of the gods. Some accounts suggest that the oldest known imagery of the caduceus has its roots in Mesopotamia with the Sumerian god Ningishzida; his symbol, a staff with two snakes intertwined around it, dates back to 4000 BC to 3000 BC. As a symbolic object, it represents Hermes (or the Roman Mercury), and by extension trades, occupations, or undertakings associated with the god. In later Antiquity, the caduceus provided the basis for the astrological symbol representing th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
April Fools' Day
April Fools' Day or All Fools' Day is an annual custom on 1 April consisting of practical jokes and hoaxes. Jokesters often expose their actions by shouting "April Fools!" at the recipient. Mass media can be involved in these pranks, which may be revealed as such the following day. The custom of setting aside a day for playing harmless pranks upon one's neighbour has been relatively common in the world historically. Origins Although the origins of April Fools’ is unknown, there are many theories surrounding it. A disputed association between 1 April and foolishness is in Geoffrey Chaucer's '' The Canterbury Tales'' (1392). In the " Nun's Priest's Tale", a vain cock Chauntecleer is tricked by a fox on "Since March began thirty days and two," i.e. 32 days since March began, which is 1 April. However, it is not clear that Chaucer was referencing 1 April since the text of the "Nun's Priest's Tale" also states that the story takes place on the day when the sun is "in the sign ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Star
A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in which case they are called ''visual binaries''. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as spectroscopy (''spectroscopic binaries'') or astrometry (''astrometric binaries''). If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other; these pairs are called ''eclipsing binaries'', or, together with other binaries that change brightness as they orbit, ''photometric binaries''. If components in binary star systems are close enough they can gravitationally distort their mutual outer stellar atmospheres. In some cases, thes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interstellar Medium
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space. The energy that occupies the same volume, in the form of electromagnetic radiation, is the interstellar radiation field. The interstellar medium is composed of multiple phases distinguished by whether matter is ionic, atomic, or molecular, and the temperature and density of the matter. The interstellar medium is composed, primarily, of hydrogen, followed by helium with trace amounts of carbon, oxygen, and nitrogen. The thermal pressures of these phases are in rough equilibrium with one another. Magnetic fields and turbulent motions also provide pressure in the ISM, and are typically more important, dynamically, than the thermal pressure is. In the interstellar medium, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Satellites
A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''moons'', a derivation from the Moon of Earth. In the Solar System, there are six planetary satellite systems containing 209 known natural satellites altogether. Seven objects commonly considered dwarf planets by astronomers are also known to have natural satellites: , Pluto, Haumea, , Makemake, , and Eris. , there are 442 other minor planets known to have natural satellites. A planet usually has at least around 10,000 times the mass of any natural satellites that orbit it, with a correspondingly much larger diameter. The Earth–Moon system is a unique exception in the Solar System; at 3,474 kilometres (2,158 miles) across, the Moon is 0.273 times the diameter of Earth and about of its mass. The next largest ratios are the Neptune–T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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