Amalthea (moon)
Amalthea is the third moon of Jupiter in order of distance from the planet. It was discovered on 9 September 1892, by Edward Emerson Barnard and named after Amalthea, a nymph in Greek mythology, it is known as Jupiter V. Amalthea is in a close orbit around Jupiter and is within the outer edge of the Amalthea Gossamer Ring, formed from dust ejected from its surface. From its surface, Jupiter would appear 46.5 degrees in diameter. Amalthea is the largest of the inner satellites of Jupiter. Irregularly shaped and reddish in color, it is thought to consist of porous water ice with unknown amounts of other materials, its surface features include large ridges. Amalthea was photographed in 1979 by the Voyager 1 and 2 spacecraft, in more detail, by the Galileo orbiter in the 1990s. Amalthea was discovered on 9 September 1892, by Edward Emerson Barnard using the 36 inch refractor telescope at Lick Observatory, it was the last planetary satellite to be discovered by direct visual observation and was the first new satellite of Jupiter since Galileo Galilei's discovery of the Galilean satellites in 1610.
Amalthea is named after the nymph Amalthea from Greek mythology, who nursed the infant Zeus with goat's milk. Its Roman numeral designation is Jupiter V; the name "Amalthea" was not formally adopted by the IAU until 1976, although it had been in informal use for many decades. The name was suggested by Camille Flammarion. Before 1976, Amalthea was most known as Jupiter V. Amalthea orbits Jupiter at a distance of 181 000 km; the orbit of Amalthea has an eccentricity of 0.003 and an inclination of 0.37° relative to the equator of Jupiter. Such appreciably nonzero values of inclination and eccentricity, though still small, are unusual for an inner satellite and can be explained by the influence of the innermost Galilean satellite, Io: in the past Amalthea has passed through several mean-motion resonances with Io that have excited its inclination and eccentricity. Amalthea's orbit lies near the outer edge of the Amalthea Gossamer Ring, composed of the dust ejected from the satellite; the surface of Amalthea is red.
The reddish color may be due to sulfur originating from some other non-ice material. Bright patches of less red tint appear on the major slopes of Amalthea, but the nature of this color is unknown; the surface of Amalthea is brighter than surfaces of other inner satellites of Jupiter. There is a substantial asymmetry between leading and trailing hemispheres: the leading hemisphere is 1.3 times brighter than the trailing one. The asymmetry is caused by the higher velocity and frequency of impacts on the leading hemisphere, which excavate a bright material—presumably ice—from the interior of the moon. Amalthea is irregularly shaped, with the best ellipsoidal approximation being 250 × 146 × 128 km. From this, Amalthea's surface area is between 88,000 and 170,000 square kilometers, or somewhere near 130,000. Like all other inner moons of Jupiter it is tidally locked with the planet, the long axis pointing towards Jupiter at all times, its surface is scarred by craters, some of which are large relative to the size of the moon: Pan, the largest crater, measures 100 km across and is at least 8 km deep.
Another crater, measures 80 km across and is twice as deep as Pan. Amalthea has several prominent bright spots, they are Ida Facula, with width reaching up to 25 km. They are located on the edge of ridges. Amalthea's irregular shape and large size led in the past to a conclusion that it is a strong, rigid body, where it was argued that a body composed of ices or other weak materials would have been pulled into a more spherical shape by its own gravity. However, on 5 November 2002, the Galileo orbiter made a targeted flyby that came within 160 km of Amalthea and the deflection of its orbit was used to compute the moon's mass. In the end, Amalthea's density was found to be as low as 0.86 g/cm3, so it must be either a icy body or porous "rubble pile" or, more something in between. Recent measurements of infrared spectra from the Subaru telescope suggest that the moon indeed contains hydrous minerals, indicating that it cannot have formed in its current position, since the hot primordial Jupiter would have melted it.
It is therefore to have formed farther from the planet or to be a captured Solar System body. No images were taken during this flyby, the resolution of other available images is low. Amalthea radiates more heat than it receives from the Sun, due to the influence of Jovian heat flux, sunlight reflected from the planet, charged particle bombardment; this is a trait shared with Io, although for different reasons. There are four named geological features on Amalthea: two faculae; the faculae are located on the edge of a ridge on the anti-Jupiter side of Amalthea. Due to tidal force from Jupiter and Amalthea's low density and irregular shape, the escape velocity at its surface points closest to and furthest from Jupiter is no more than 1 m/s and dust can escape from it after, e.g. micrometeorite impacts. During its flyby of Amalthea, the Galileo orbiter's star scanner detected nine fla
Crete
Crete is the largest and most populous of the Greek islands, the 88th largest island in the world and the fifth largest island in the Mediterranean Sea, after Sicily, Sardinia and Corsica. Crete and a number of surrounding islands and islets constitute the region of Crete, one of the 13 top-level administrative units of Greece; the capital and the largest city is Heraklion. As of 2011, the region had a population of 623,065. Crete forms a significant part of the economy and cultural heritage of Greece, while retaining its own local cultural traits, it was once the centre of the Minoan civilisation, the earliest known civilisation in Europe. The palace of Knossos lies in Crete; the island is first referred to as Kaptara in texts from the Syrian city of Mari dating from the 18th century BC, repeated in Neo-Assyrian records and the Bible. It was known in ancient Egyptian as Keftiu suggesting a similar Minoan name for the island; the current name of Crete is thought to be first attested in Mycenaean Greek texts written in Linear B, through the words ke-re-te, ke-re-si-jo, "Cretan".
In Ancient Greek, the name Crete first appears in Homer's Odyssey. Its etymology is unknown. One proposal derives it from a hypothetical Luwian word, *kursatta. In Latin, it became Creta; the original Arabic name of Crete was Iqrīṭiš, but after the Emirate of Crete's establishment of its new capital at ربض الخندق Rabḍ al-Ḫandaq, both the city and the island became known as Χάνδαξ or Χάνδακας, which gave Latin and Venetian Candia, from which were derived French Candie and English Candy or Candia. Under Ottoman rule, in Ottoman Turkish, Crete was called Girit. Crete is the fifth largest island in the Mediterranean Sea, it is located in the southern part of the Aegean Sea separating the Aegean from the Libyan Sea. The island has an elongated shape: it spans 260 km from east to west, is 60 km at its widest point, narrows to as little as 12 km. Crete covers an area of 8,336 km2, with a coastline of 1,046 km, it lies 160 km south of the Greek mainland. Crete is mountainous, its character is defined by a high mountain range crossing from west to east, formed by three different groups of mountains: The White Mountains or Lefka Ori 2,454 m The Idi Range (Psiloritis 35.18°N 24.82°E / 35.18.
The island has a number of gorges, such as the Samariá Gorge, Imbros Gorge, Kourtaliotiko Gorge, Ha Gorge, Platania Gorge, the Gorge of the Dead and Richtis Gorge and waterfall at Exo Mouliana in Sitia. The rivers of Crete include the Ieropotamos River, the Koiliaris, the Anapodiaris, the Almiros, the Giofyros, Megas Potamos. There are only two freshwater lakes in Crete: Lake Kournas and Lake Agia, which are both in Chania regional unit. Lake Voulismeni at the coast, at Aghios Nikolaos, was a freshwater lake but is now connected to the sea, in Lasithi. Lakes that were created by dams exist in Crete. There are three: the lake of Aposelemis Dam, the lake of Potamos Dam, the lake of Mpramiana Dam. A large number of islands and rocks hug the coast of Crete. Many are visited by tourists, some are only visited by biologists; some are environmentally protected. A small sample of the islands includes: Gramvousa the pirate island opposite the Balo lagoon Elafonisi, which commemorates a shipwreck and an Ottoman massacre Chrysi island, which hosts the largest natural Lebanon cedar forest in Europe Paximadia island where the god Apollo and the goddess Artemis were born The Venetian fort and leper colony at Spinalonga opposite the beach and shallow waters of Elounda Dionysades islands which are in an environmentally protected region together the Palm Beach Forest of Vai in the municipality of Sitia, LasithiOff the south coast, the island of Gavdos is located 26 nautical miles south of Hora Sfakion and is the southernmost point of Europe.
Crete straddles two climatic zones, the Mediterranean and the North African falling within the former. As such, the climate in Crete is Mediterranean; the atmosphere can be quite humid, depending on the proximity to the sea, while winter is mild. Snowfall is rare in the low-lying areas. While some mountain tops are snow-capped for most of the year, near the coast snow only stays on the ground for a few minutes or hours. However, a exceptional cold snap swept the island in February 2004, during which period the whole island was blanketed with snow. During the Cretan summer, average temperatures reach the high 20s-low 30s Celsius, with maxima touching the upper 30s-mid 40s; the south coast, including the Mesara Pla
Ecliptic
The ecliptic is the mean plane of the apparent path in the Earth's sky that the Sun follows over the course of one year. This plane of reference is coplanar with Earth's orbit around the Sun; the ecliptic is not noticeable from Earth's surface because the planet's rotation carries the observer through the daily cycles of sunrise and sunset, which obscure the Sun's apparent motion against the background of stars during the year. The motions as described above are simplifications. Due to the movement of Earth around the Earth–Moon center of mass, the apparent path of the Sun wobbles with a period of about one month. Due to further perturbations by the other planets of the Solar System, the Earth–Moon barycenter wobbles around a mean position in a complex fashion; the ecliptic is the apparent path of the Sun throughout the course of a year. Because Earth takes one year to orbit the Sun, the apparent position of the Sun takes one year to make a complete circuit of the ecliptic. With more than 365 days in one year, the Sun moves a little less than 1° eastward every day.
This small difference in the Sun's position against the stars causes any particular spot on Earth's surface to catch up with the Sun about four minutes each day than it would if Earth would not orbit. Again, this is a simplification, based on a hypothetical Earth that orbits at uniform speed around the Sun; the actual speed with which Earth orbits the Sun varies during the year, so the speed with which the Sun seems to move along the ecliptic varies. For example, the Sun is north of the celestial equator for about 185 days of each year, south of it for about 180 days; the variation of orbital speed accounts for part of the equation of time. Because Earth's rotational axis is not perpendicular to its orbital plane, Earth's equatorial plane is not coplanar with the ecliptic plane, but is inclined to it by an angle of about 23.4°, known as the obliquity of the ecliptic. If the equator is projected outward to the celestial sphere, forming the celestial equator, it crosses the ecliptic at two points known as the equinoxes.
The Sun, in its apparent motion along the ecliptic, crosses the celestial equator at these points, one from south to north, the other from north to south. The crossing from south to north is known as the vernal equinox known as the first point of Aries and the ascending node of the ecliptic on the celestial equator; the crossing from north to south is descending node. The orientation of Earth's axis and equator are not fixed in space, but rotate about the poles of the ecliptic with a period of about 26,000 years, a process known as lunisolar precession, as it is due to the gravitational effect of the Moon and Sun on Earth's equatorial bulge; the ecliptic itself is not fixed. The gravitational perturbations of the other bodies of the Solar System cause a much smaller motion of the plane of Earth's orbit, hence of the ecliptic, known as planetary precession; the combined action of these two motions is called general precession, changes the position of the equinoxes by about 50 arc seconds per year.
Once again, this is a simplification. Periodic motions of the Moon and apparent periodic motions of the Sun cause short-term small-amplitude periodic oscillations of Earth's axis, hence the celestial equator, known as nutation; this adds a periodic component to the position of the equinoxes. Obliquity of the ecliptic is the term used by astronomers for the inclination of Earth's equator with respect to the ecliptic, or of Earth's rotation axis to a perpendicular to the ecliptic, it is about 23.4° and is decreasing 0.013 degrees per hundred years due to planetary perturbations. The angular value of the obliquity is found by observation of the motions of Earth and other planets over many years. Astronomers produce new fundamental ephemerides as the accuracy of observation improves and as the understanding of the dynamics increases, from these ephemerides various astronomical values, including the obliquity, are derived; until 1983 the obliquity for any date was calculated from work of Newcomb, who analyzed positions of the planets until about 1895: ε = 23° 27′ 08″.26 − 46″.845 T − 0″.0059 T2 + 0″.00181 T3 where ε is the obliquity and T is tropical centuries from B1900.0 to the date in question.
From 1984, the Jet Propulsion Laboratory's DE series of computer-generated ephemerides took over as the fundamental ephemeris of the Astronomical Almanac. Obliquity based on DE200, which analyzed observations from 1911 to 1979, was calculated: ε = 23° 26′ 21″.45 − 46″.815 T − 0″.0006 T2 + 0″.00181 T3 where hereafter T is Julian centuries from J2000.0. JPL's fundamental ephemerides have been continually updated; the Astronomical Almanac for 2010 specifies:ε = 23° 26′ 21″.406 − 46″.836769 T − 0″.0001831 T2 + 0″.00200340 T3 − 0″.576×10−6 T4 − 4″.34×10−8 T5 These expressions for the obliquity are intended for high precision over a short time span ± several centuries. J. Laskar computed an expression to order T10 good to 0″.04/1000 years over 10,000 years. All of these expressions are for the mean obliquity, that is, without the nutation of the equator included; the true or instantaneous obliquity includes the nutation. Most of the major bodies of the Solar System o
Seth Barnes Nicholson
Seth Barnes Nicholson was an American astronomer. Nicholson was born in Springfield and was raised in rural Illinois, he was educated at Drake University. In 1914, at the University of California's Lick Observatory, while observing the discovered Jupiter moon Pasiphaë, he discovered a new one, whose orbit he computed for his Ph. D. thesis in 1915. He spent his entire career at Mount Wilson Observatory, where he discovered three more Jovian moons: Lysithea and Carme in 1938 and Ananke in 1951, as well as a Trojan asteroid, 1647 Menelaus, computed orbits of several comets and of Pluto. Sinope, Lysithea and Ananke were designated as "Jupiter IX", "Jupiter X", "Jupiter XI" and "Jupiter XII", they were not given their present names until 1975. Nicholson himself declined to propose names. At Mt. Wilson, his main assignment concerned solar activity and he produced for decades annual reports on sunspot activity, he made a number of eclipse expeditions to measure the brightness and temperature of the Sun's corona.
In the early 1920s, he and Edison Pettit made the first systematic infrared observations of celestial objects. They used a vacuum thermocouple to measure the infrared radiation and thus the temperature of the Moon which led to the theory that the Moon was covered with a thin layer of dust acting as an insulator, of the planets and stars, their temperatures measurements of nearby giant stars led to some of the first determinations of stellar diameters. Nicholson, together with astronomer George Ellery Hale, lend their name to the "Hale-Nicholson law" concerning the magnetic polarity of sunspots. From 1943 to 1955, he served as editor of the Publications of the Astronomical Society of the Pacific, of which he was twice president, he died in Los Angeles. Awarded the Bruce Medal The Asteroid 1831 Nicholson, the crater Nicholson on the Moon, the crater Nicholson on Mars, Nicholson Regio on Ganymede were named after him. Works by or about Seth Barnes Nicholson at Internet Archive Seth Barnes Nicholson — Biographical Memoirs of the National Academy of Sciences
California
California is a state in the Pacific Region of the United States. With 39.6 million residents, California is the most populous U. S. the third-largest by area. The state capital is Sacramento; the Greater Los Angeles Area and the San Francisco Bay Area are the nation's second and fifth most populous urban regions, with 18.7 million and 9.7 million residents respectively. Los Angeles is California's most populous city, the country's second most populous, after New York City. California has the nation's most populous county, Los Angeles County, its largest county by area, San Bernardino County; the City and County of San Francisco is both the country's second-most densely populated major city after New York City and the fifth-most densely populated county, behind only four of the five New York City boroughs. California's $3.0 trillion economy is larger than that of any other state, larger than those of Texas and Florida combined, the largest sub-national economy in the world. If it were a country, California would be the 5th largest economy in the world, the 36th most populous as of 2017.
The Greater Los Angeles Area and the San Francisco Bay Area are the nation's second- and third-largest urban economies, after the New York metropolitan area. The San Francisco Bay Area PSA had the nation's highest GDP per capita in 2017 among large PSAs, is home to three of the world's ten largest companies by market capitalization and four of the world's ten richest people. California is considered a global trendsetter in popular culture, innovation and politics, it is considered the origin of the American film industry, the hippie counterculture, fast food, the Internet, the personal computer, among others. The San Francisco Bay Area and the Greater Los Angeles Area are seen as global centers of the technology and entertainment industries, respectively. California has a diverse economy: 58% of the state's economy is centered on finance, real estate services and professional, scientific and technical business services. Although it accounts for only 1.5% of the state's economy, California's agriculture industry has the highest output of any U.
S. state. California is bordered by Oregon to the north and Arizona to the east, the Mexican state of Baja California to the south; the state's diverse geography ranges from the Pacific Coast in the west to the Sierra Nevada mountain range in the east, from the redwood–Douglas fir forests in the northwest to the Mojave Desert in the southeast. The Central Valley, a major agricultural area, dominates the state's center. Although California is well-known for its warm Mediterranean climate, the large size of the state results in climates that vary from moist temperate rainforest in the north to arid desert in the interior, as well as snowy alpine in the mountains. Over time and wildfires have become more pervasive features. What is now California was first settled by various Native Californian tribes before being explored by a number of European expeditions during the 16th and 17th centuries; the Spanish Empire claimed it as part of Alta California in their New Spain colony. The area became a part of Mexico in 1821 following its successful war for independence but was ceded to the United States in 1848 after the Mexican–American War.
The western portion of Alta California was organized and admitted as the 31st state on September 9, 1850. The California Gold Rush starting in 1848 led to dramatic social and demographic changes, with large-scale emigration from the east and abroad with an accompanying economic boom; the word California referred to the Baja California Peninsula of Mexico. The name derived from the mythical island California in the fictional story of Queen Calafia, as recorded in a 1510 work The Adventures of Esplandián by Garci Rodríguez de Montalvo; this work was the fifth in a popular Spanish chivalric romance series that began with Amadis de Gaula. Queen Calafia's kingdom was said to be a remote land rich in gold and pearls, inhabited by beautiful black women who wore gold armor and lived like Amazons, as well as griffins and other strange beasts. In the fictional paradise, the ruler Queen Calafia fought alongside Muslims and her name may have been chosen to echo the title of a Muslim leader, the Caliph. It's possible.
Know ye that at the right hand of the Indies there is an island called California close to that part of the Terrestrial Paradise, inhabited by black women without a single man among them, they lived in the manner of Amazons. They were robust of body with great virtue; the island itself is one of the wildest in the world on account of the craggy rocks. Shortened forms of the state's name include CA, Cal. Calif. and US-CA. Settled by successive waves of arrivals during the last 10,000 years, California was one of the most culturally and linguistically diverse areas in pre-Columbian North America. Various estimates of the native population range from 100,000 to 300,000; the Indigenous peoples of California included more than 70 distinct groups of Native Americans, ranging from large, settled populations living on the coast to groups in the interior. California groups were diverse in their political organization with bands, villages, on the resource-rich coasts, large chiefdoms, such as the Chumash and Salinan.
Trade, intermarriage a
Escape velocity
In physics, escape velocity is the minimum speed needed for a free object to escape from the gravitational influence of a massive body. It is slower the further away from the body an object is, slower for less massive bodies; the escape velocity from Earth is about 11.186 km/s at the surface. More escape velocity is the speed at which the sum of an object's kinetic energy and its gravitational potential energy is equal to zero. With escape velocity in a direction pointing away from the ground of a massive body, the object will move away from the body, slowing forever and approaching, but never reaching, zero speed. Once escape velocity is achieved, no further impulse need to be applied for it to continue in its escape. In other words, if given escape velocity, the object will move away from the other body, continually slowing, will asymptotically approach zero speed as the object's distance approaches infinity, never to come back. Speeds higher than escape velocity have a positive speed at infinity.
Note that the minimum escape velocity assumes that there is no friction, which would increase the required instantaneous velocity to escape the gravitational influence, that there will be no future acceleration or deceleration, which would change the required instantaneous velocity. For a spherically symmetric, massive body such as a star, or planet, the escape velocity for that body, at a given distance, is calculated by the formula v e = 2 G M r, where G is the universal gravitational constant, M the mass of the body to be escaped from, r the distance from the center of mass of the body to the object; the relationship is independent of the mass of the object escaping the massive body. Conversely, a body that falls under the force of gravitational attraction of mass M, from infinity, starting with zero velocity, will strike the massive object with a velocity equal to its escape velocity given by the same formula; when given an initial speed V greater than the escape speed v e, the object will asymptotically approach the hyperbolic excess speed v ∞, satisfying the equation: v ∞ 2 = V 2 − v e 2.
In these equations atmospheric friction is not taken into account. A rocket moving out of a gravity well does not need to attain escape velocity to escape, but could achieve the same result at any speed with a suitable mode of propulsion and sufficient propellant to provide the accelerating force on the object to escape. Escape velocity is only required to send a ballistic object on a trajectory that will allow the object to escape the gravity well of the mass M; the existence of escape velocity is a consequence of conservation of energy and an energy field of finite depth. For an object with a given total energy, moving subject to conservative forces it is only possible for the object to reach combinations of locations and speeds which have that total energy. By adding speed to the object it expands the possible locations that can be reached, with enough energy, they become infinite. For a given gravitational potential energy at a given position, the escape velocity is the minimum speed an object without propulsion needs to be able to "escape" from the gravity.
Escape velocity is a speed because it does not specify a direction: no matter what the direction of travel is, the object can escape the gravitational field. The simplest way of deriving the formula for escape velocity is to use conservation of energy. For the sake of simplicity, unless stated otherwise, we assume that an object is attempting to escape from a uniform spherical planet by moving away from it and that the only significant force acting on the moving object is the planet's gravity. In its initial state, i, imagine that a spaceship of mass m is at a distance r from the center of mass of the planet, whose mass is M, its initial speed is equal to v e. At its final state, f, it will be an infinite distance away from the planet, its speed will be negligibly small and assumed to be 0. Kinetic energy K and gravitational potential energy Ug are the only types of energy that we will deal with, so by the conservation of energy, i = f Kƒ = 0 because final velocity is zero, Ugƒ = 0 because its final distance is infinity, so ⇒ 1 2 m v e 2 + − G M m r
Galilean moons
The Galilean moons are the four largest moons of Jupiter—Io, Europa and Callisto. They were first seen by Galileo Galilei in December 1609 or January 1610, recognized by him as satellites of Jupiter in March 1610, they were the first objects found to orbit another planet. They are among the largest objects in the Solar System with the exception of the Sun and the eight planets, with a radius larger than any of the dwarf planets. Ganymede is the largest moon in the Solar System, is bigger than the planet Mercury, though only around half as massive; the three inner moons—Io, Ganymede—are in a 4:2:1 orbital resonance with each other. Because of their much smaller size, therefore weaker self-gravitation, all of Jupiter's remaining moons have irregular forms rather than a spherical shape; the Galilean moons were observed in either 1609 or 1610 when Galileo made improvements to his telescope, which enabled him to observe celestial bodies more distinctly than ever. Galileo's observations showed the importance of the telescope as a tool for astronomers by proving that there were objects in space that cannot be seen by the naked eye.
The discovery of celestial bodies orbiting something other than Earth dealt a serious blow to the then-accepted Ptolemaic world system, a geocentric theory in which everything orbits around Earth. Galileo named his discovery the Cosmica Sidera, but the names that prevailed were chosen by Simon Marius. Marius discovered the moons independently at nearly the same time as Galileo, gave them their present names, derived from the lovers of Zeus, which were suggested by Johannes Kepler, in his Mundus Jovialis, published in 1614; as a result of improvements Galileo Galilei made to the telescope, with a magnifying capability of 20×, he was able to see celestial bodies more distinctly than was possible before. This allowed Galilei to observe in either December 1609 or January 1610 what came to be known as the Galilean moons. On January 7, 1610, Galileo wrote a letter containing the first mention of Jupiter's moons. At the time, he saw only three of them, he believed them to be fixed stars near Jupiter.
He continued to observe these celestial orbs from January 8 to March 2, 1610. In these observations, he discovered a fourth body, observed that the four were not fixed stars, but rather were orbiting Jupiter. Galileo's discovery proved the importance of the telescope as a tool for astronomers by showing that there were objects in space to be discovered that until had remained unseen by the naked eye. More the discovery of celestial bodies orbiting something other than Earth dealt a blow to the then-accepted Ptolemaic world system, which held that Earth was at the center of the universe and all other celestial bodies revolved around it. Galileo's Sidereus Nuncius, which announced celestial observations through his telescope, does not explicitly mention Copernican heliocentrism, a theory that placed the Sun at the center of the universe. Galileo accepted the Copernican theory. A Chinese historian of astronomy, Xi Zezong, has claimed that a "small reddish star" observed near Jupiter in 362 BCE by Chinese astronomer Gan De may have been Ganymede, predating Galileo's discovery by around two millennia.
In 1605, Galileo had been employed as a mathematics tutor for Cosimo de' Medici. In 1609, Cosimo became Grand Duke Cosimo II of Tuscany. Galileo, seeking patronage from his now-wealthy former student and his powerful family, used the discovery of Jupiter's moons to gain it. On February 13, 1610, Galileo wrote to the Grand Duke's secretary: "God graced me with being able, through such a singular sign, to reveal to my Lord my devotion and the desire I have that his glorious name live as equal among the stars, since it is up to me, the first discoverer, to name these new planets, I wish, in imitation of the great sages who placed the most excellent heroes of that age among the stars, to inscribe these with the name of the Most Serene Grand Duke." Galileo asked whether he should name the moons the "Cosmian Stars", after Cosimo alone, or the "Medician Stars", which would honor all four brothers in the Medici clan. The secretary replied. On March 12, 1610, Galileo wrote his dedicatory letter to the Duke of Tuscany, the next day sent a copy to the Grand Duke, hoping to obtain the Grand Duke's support as as possible.
On March 19, he sent the telescope he had used to first view Jupiter's moons to the Grand Duke, along with an official copy of Sidereus Nuncius that, following the secretary's advice, named the four moons the Medician Stars. In his dedicatory introduction, Galileo wrote: Scarcely have the immortal graces of your soul begun to shine forth on earth than bright stars offer themselves in the heavens which, like tongues, will speak of and celebrate your most excellent virtues for all time. Behold, four stars reserved for your illustrious name... which... make their journeys and orbits with a marvelous speed around the star of Jupiter... Like children of the same family... Indeed, it appears the Maker of the Stars himself, by clear arguments, admonished me to call these new planets by the illustrious name of Your Highness before all others. Galileo called his discovery the Cosmica Sidera, in honour of Cosimo II de' Medici. At Cosimo's suggestion, Galileo changed the name to Medicea Sidera, honouring all four Medici brothers.
The discovery was announced in the Sidereus Nuncius, published in Venice in March 1610, less than two months after the first observations. Other names put forward include: I. Principharus (for the "prince" of
