Asteroids are minor planets of the inner Solar System. Larger asteroids have been called planetoids; these terms have been applied to any astronomical object orbiting the Sun that did not resemble a planet-like disc and was not observed to have characteristics of an active comet such as a tail. As minor planets in the outer Solar System were discovered they were found to have volatile-rich surfaces similar to comets; as a result, they were distinguished from objects found in the main asteroid belt. In this article, the term "asteroid" refers to the minor planets of the inner Solar System including those co-orbital with Jupiter. There exist millions of asteroids, many thought to be the shattered remnants of planetesimals, bodies within the young Sun's solar nebula that never grew large enough to become planets; the vast majority of known asteroids orbit within the main asteroid belt located between the orbits of Mars and Jupiter, or are co-orbital with Jupiter. However, other orbital families exist with significant populations, including the near-Earth objects.
Individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups: C-type, M-type, S-type. These were named after and are identified with carbon-rich and silicate compositions, respectively; the sizes of asteroids varies greatly. Asteroids are differentiated from meteoroids. In the case of comets, the difference is one of composition: while asteroids are composed of mineral and rock, comets are composed of dust and ice. Furthermore, asteroids formed closer to the sun; the difference between asteroids and meteoroids is one of size: meteoroids have a diameter of one meter or less, whereas asteroids have a diameter of greater than one meter. Meteoroids can be composed of either cometary or asteroidal materials. Only one asteroid, 4 Vesta, which has a reflective surface, is visible to the naked eye, this only in dark skies when it is favorably positioned. Small asteroids passing close to Earth may be visible to the naked eye for a short time; as of October 2017, the Minor Planet Center had data on 745,000 objects in the inner and outer Solar System, of which 504,000 had enough information to be given numbered designations.
The United Nations declared 30 June as International Asteroid Day to educate the public about asteroids. The date of International Asteroid Day commemorates the anniversary of the Tunguska asteroid impact over Siberia, Russian Federation, on 30 June 1908. In April 2018, the B612 Foundation reported "It's 100 percent certain we'll be hit, but we're not 100 percent sure when." In 2018, physicist Stephen Hawking, in his final book Brief Answers to the Big Questions, considered an asteroid collision to be the biggest threat to the planet. In June 2018, the US National Science and Technology Council warned that America is unprepared for an asteroid impact event, has developed and released the "National Near-Earth Object Preparedness Strategy Action Plan" to better prepare. According to expert testimony in the United States Congress in 2013, NASA would require at least five years of preparation before a mission to intercept an asteroid could be launched; the first asteroid to be discovered, was considered to be a new planet.
This was followed by the discovery of other similar bodies, with the equipment of the time, appeared to be points of light, like stars, showing little or no planetary disc, though distinguishable from stars due to their apparent motions. This prompted the astronomer Sir William Herschel to propose the term "asteroid", coined in Greek as ἀστεροειδής, or asteroeidēs, meaning'star-like, star-shaped', derived from the Ancient Greek ἀστήρ astēr'star, planet'. In the early second half of the nineteenth century, the terms "asteroid" and "planet" were still used interchangeably. Overview of discovery timeline: 10 by 1849 1 Ceres, 1801 2 Pallas – 1802 3 Juno – 1804 4 Vesta – 1807 5 Astraea – 1845 in 1846, planet Neptune was discovered 6 Hebe – July 1847 7 Iris – August 1847 8 Flora – October 1847 9 Metis – 25 April 1848 10 Hygiea – 12 April 1849 tenth asteroid discovered 100 asteroids by 1868 1,000 by 1921 10,000 by 1989 100,000 by 2005 ~700,000 by 2015 Asteroid discovery methods have improved over the past two centuries.
In the last years of the 18th century, Baron Franz Xaver von Zach organized a group of 24 astronomers to search the sky for the missing planet predicted at about 2.8 AU from the Sun by the Titius-Bode law because of the discovery, by Sir William Herschel in 1781, of the planet Uranus at the distance predicted by the law. This task required that hand-drawn sky charts be prepared for all stars in the zodiacal band down to an agreed-upon limit of faintness. On subsequent nights, the sky would be charted again and any moving object would be spotted; the expected motion of the missing planet was about 30 seconds of arc per hour discernible by observers. The first object, was not discovered by a member of the group, but rather by accident in 1801 by Giuseppe Piazzi, director of the observatory of Palermo in Sicily, he discovered a new star-like object in Taurus and followed the displacement of this object during several nights. That year, Carl Friedrich Gauss used these observations to calculate the orbit of this unknown object, found to be between the planets Mars and Jupiter.
Piazzi named it after Ceres, the Roman goddess of agriculture. Three other asteroids (2 Pallas, 3 Juno, 4 Ves
1291 Phryne, provisional designation 1933 RA, is an Eoan asteroid from the outer regions of the asteroid belt 27 kilometers in diameter. It was discovered on 15 September 1933, by Belgian astronomer Eugène Delporte at the Royal Observatory of Belgium in Uccle; the asteroid was named after the ancient Greek courtesan Phryne. Phryne is a member the Eos family, the largest asteroid family in the outer main belt consisting of nearly 10,000 asteroids, it orbits the Sun at a distance of 2.7–3.3 AU once every 5 years and 3 months. Its orbit has an eccentricity of 0.09 and an inclination of 9° with respect to the ecliptic. The body's observation arc begins with its first identification as A907 TA at Heidelberg Observatory in October 1907. Phryne is an assumed stony S-type asteroid, while the Eon family's overall spectral type is that of a K-type. In May 1984, a rotational lightcurve of Phryne was obtained by astronomer Richard Binzel. Lightcurve analysis gave a well-defined rotation period of 5.55 hours with a brightness variation of 0.86 magnitude.
In August 2006, from photometric observations by French amateur astronomer Pierre Antonini gave a period of 5.58410 hours and an amplitude of 0.38 magnitude In 2011, a modeled lightcurve using data from the Uppsala Asteroid Photometric Catalogue and other sources gave a period 5.58414 hours, as well as two spin axis of and in ecliptic coordinates. In 2017, a new study of the same international collaboration about the rotational states of Eoan asteroids gave a revised shape model with a period of 5.584139 hours and two spin axis of and. According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Phryne measures between 24.954 and 31.13 kilometers in diameter and its surface has an albedo between 0.127 and 0.1818. The Collaborative Asteroid Lightcurve Link derives an albedo of 0.1355 and a diameter of 26.52 kilometers based on an absolute magnitude of 10.67. This minor planet was named after Phryne, the beautiful ancient Greek courtesan of the 4th century B.
C. She was the model for the statue Aphrodite of Knidos by ancient Greek sculptor Praxiteles, her lover, it was the first nude statue of a woman from ancient Greece. The official naming citation was mentioned in The Names of the Minor Planets by Paul Herget in 1955. Asteroid Lightcurve Database, query form Dictionary of Minor Planet Names, Google books Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend Discovery Circumstances: Numbered Minor Planets - – Minor Planet Center 1291 Phryne at the JPL Small-Body Database Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters
Right ascension is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the point above the earth in question. When paired with declination, these astronomical coordinates specify the direction of a point on the celestial sphere in the equatorial coordinate system. An old term, right ascension refers to the ascension, or the point on the celestial equator that rises with any celestial object as seen from Earth's equator, where the celestial equator intersects the horizon at a right angle, it contrasts with oblique ascension, the point on the celestial equator that rises with any celestial object as seen from most latitudes on Earth, where the celestial equator intersects the horizon at an oblique angle. Right ascension is the celestial equivalent of terrestrial longitude. Both right ascension and longitude measure an angle from a primary direction on an equator. Right ascension is measured from the Sun at the March equinox i.e. the First Point of Aries, the place on the celestial sphere where the Sun crosses the celestial equator from south to north at the March equinox and is located in the constellation Pisces.
Right ascension is measured continuously in a full circle from that alignment of Earth and Sun in space, that equinox, the measurement increasing towards the east. As seen from Earth, objects noted to have 12h RA are longest visible at the March equinox. On those dates at midnight, such objects will reach their highest point. How high depends on their declination. Any units of angular measure could have been chosen for right ascension, but it is customarily measured in hours and seconds, with 24h being equivalent to a full circle. Astronomers have chosen this unit to measure right ascension because they measure a star's location by timing its passage through the highest point in the sky as the Earth rotates; the line which passes through the highest point in the sky, called the meridian, is the projection of a longitude line onto the celestial sphere. Since a complete circle contains 24h of right ascension or 360°, 1/24 of a circle is measured as 1h of right ascension, or 15°. A full circle, measured in right-ascension units, contains 24 × 60 × 60 = 86400s, or 24 × 60 = 1440m, or 24h.
Because right ascensions are measured in hours, they can be used to time the positions of objects in the sky. For example, if a star with RA = 1h 30m 00s is at its meridian a star with RA = 20h 00m 00s will be on the/at its meridian 18.5 sidereal hours later. Sidereal hour angle, used in celestial navigation, is similar to right ascension, but increases westward rather than eastward. Measured in degrees, it is the complement of right ascension with respect to 24h, it is important not to confuse sidereal hour angle with the astronomical concept of hour angle, which measures angular distance of an object westward from the local meridian. The Earth's axis rotates westward about the poles of the ecliptic, completing one cycle in about 26,000 years; this movement, known as precession, causes the coordinates of stationary celestial objects to change continuously, if rather slowly. Therefore, equatorial coordinates are inherently relative to the year of their observation, astronomers specify them with reference to a particular year, known as an epoch.
Coordinates from different epochs must be mathematically rotated to match each other, or to match a standard epoch. Right ascension for "fixed stars" near the ecliptic and equator increases by about 3.05 seconds per year on average, or 5.1 minutes per century, but for fixed stars further from the ecliptic the rate of change can be anything from negative infinity to positive infinity. The right ascension of Polaris is increasing quickly; the North Ecliptic Pole in Draco and the South Ecliptic Pole in Dorado are always at right ascension 18h and 6h respectively. The used standard epoch is J2000.0, January 1, 2000 at 12:00 TT. The prefix "J" indicates. Prior to J2000.0, astronomers used the successive Besselian epochs B1875.0, B1900.0, B1950.0. The concept of right ascension has been known at least as far back as Hipparchus who measured stars in equatorial coordinates in the 2nd century BC, but Hipparchus and his successors made their star catalogs in ecliptic coordinates, the use of RA was limited to special cases.
With the invention of the telescope, it became possible for astronomers to observe celestial objects in greater detail, provided that the telescope could be kept pointed at the object for a period of time. The easiest way to do, to use an equatorial mount, which allows the telescope to be aligned with one of its two pivots parallel to the Earth's axis. A motorized clock drive is used with an equatorial mount to cancel out the Earth's rotation; as the equatorial mount became adopted for observation, the equatorial coordinate system, which includes right ascension, was adopted at the same time for simplicity. Equatorial mounts could be pointed at objects with known right ascension and declination by the use of setting circles; the first star catalog to use right ascen
A constellation is a group of stars that forms an imaginary outline or pattern on the celestial sphere representing an animal, mythological person or creature, a god, or an inanimate object. The origins of the earliest constellations go back to prehistory. People used them to relate stories of their beliefs, 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. Adoption of constellations has changed over time. Many have changed in shape; some became popular. Others were limited to single nations; the 48 traditional Western constellations are Greek. They are given in Aratus' work Phenomena and Ptolemy's Almagest, though their origin predates these works by several centuries. Constellations in the far southern sky were added from the 15th century until the mid-18th century when European explorers began traveling to the Southern Hemisphere. Twelve ancient constellations belong to the zodiac.
The origins of the zodiac remain uncertain. In 1928, the International Astronomical Union formally accepted 88 modern constellations, with contiguous boundaries that together cover the entire celestial sphere. Any given point in a celestial coordinate system lies in one of the modern constellations; some astronomical naming systems include the constellation where a given celestial object is found to convey its approximate location in the sky. The Flamsteed designation of a star, for example, consists of a number and the genitive form of the constellation name. Other star patterns or groups called asterisms are not constellations per se but are used by observers to navigate the night sky. Examples of bright asterisms include the Pleiades and Hyades within the constellation Taurus or Venus' Mirror in the constellation of Orion.. Some asterisms, like the False Cross, are split between two constellations; the word "constellation" comes from the Late Latin term cōnstellātiō, which can be translated as "set of stars".
The Ancient Greek word for constellation is ἄστρον. A more modern astronomical sense of the term "constellation" is as a recognisable pattern of stars whose appearance is associated with mythological characters or creatures, or earthbound animals, or objects, it can specifically denote the recognized 88 named constellations used today. Colloquial usage does not draw a sharp distinction between "constellations" and smaller "asterisms", yet the modern accepted astronomical constellations employ such a distinction. E.g. the Pleiades and the Hyades are both asterisms, each lies within the boundaries of the constellation of Taurus. Another example is the northern asterism known as the Big Dipper or the Plough, composed of the seven brightest stars within the area of the IAU-defined constellation of Ursa Major; the southern False Cross asterism includes portions of the constellations Carina and Vela and the Summer Triangle.. A constellation, viewed from a particular latitude on Earth, that never sets below the horizon is termed circumpolar.
From the North Pole or South Pole, all constellations south or north of the celestial equator are circumpolar. Depending on the definition, equatorial constellations may include those that lie between declinations 45° north and 45° south, or those that pass through the declination range of the ecliptic or zodiac ranging between 23½° north, the celestial equator, 23½° south. Although stars in constellations appear near each other in the sky, they lie at a variety of distances away from the Earth. Since stars have their own independent motions, all constellations will change over time. After tens to hundreds of thousands of years, familiar outlines will become unrecognizable. Astronomers can predict the past or future constellation outlines by measuring individual stars' common proper motions or cpm by accurate astrometry and their radial velocities by astronomical spectroscopy; the earliest evidence for the humankind's identification of constellations comes from Mesopotamian inscribed stones and clay writing tablets that date back to 3000 BC.
It seems that the bulk of the Mesopotamian constellations were created within a short interval from around 1300 to 1000 BC. Mesopotamian constellations appeared in many of the classical Greek constellations; the oldest Babylonian star catalogues of stars and constellations date back to the beginning in the Middle Bronze Age, most notably the Three Stars Each texts and the MUL. APIN, an expanded and revised version based on more accurate observation from around 1000 BC. However, the numerous Sumerian names in these catalogues suggest that they built on older, but otherwise unattested, Sumerian traditions of the Early Bronze Age; the classical Zodiac is a revision of Neo-Babylonian constellations from the 6th century BC. The Greeks adopted the Babylonian constellations in the 4th century BC. Twenty Ptolemaic constellations are from the Ancient Near East. Another ten have the same stars but different names. Biblical scholar, E. W. Bullinger interpreted some of the creatures mentioned in the books of Ezekiel and Revelation as the middle signs of the four quarters of the Zodiac, with the Lion as Leo, the Bull as Taurus, the Man representing Aquarius and the Eagle standing in for Scorpio.
The biblical Book of Job also
1217 Maximiliana, provisional designation 1932 EC, is a background asteroid from the inner regions of the asteroid belt 17 kilometers in diameter. It was discovered on 13 March 1932, by Belgian astronomer Eugène Delporte at the Royal Observatory of Belgium in Uccle; the asteroid was named in memory of Max Wolf, a German astronomer and discoverer of asteroids himself, who independently discovered this asteroid. Maximiliana is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. Based on osculating Keplerian orbital elements, the asteroid has been classified as a member of the Erigone family, a large asteroid family named after 163 Erigone, it orbits the Sun in the inner asteroid belt at a distance of 2.0–2.7 AU once every 3 years and 7 months. Its orbit has an eccentricity of 0.15 and an inclination of 5° with respect to the ecliptic. The asteroid was first observed as 1925 HC at Heidelberg in April 1925.
The body's observation arc begins in May 1925 at Heidelberg, 8 years prior to its official discovery observation at Uccle. Maximiliana is an assumed carbonaceous C-type asteroid. For comparison, members of the Erigone family are found to be C- and X-type asteroids. In March 2015, a rotational lightcurve of Maximiliana was obtained from photometric observations by Petr Pravec at Ondřejov Observatory. Lightcurve analysis gave a rotation period of 3.1987 hours with a brightness amplitude of 0.21 magnitude. Maximiliana has not been observed by any of the space-based telescopes such as the Wide-field Infrared Survey Explorer, the Akari satellite or the Infrared Astronomical Satellite IRAS; the Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous asteroids of 0.057 and calculates a diameter of 16.81 kilometers based on an absolute magnitude of 12.6. This minor planet was named in memory of Max Wolf, who independently discovered this asteroids the night before its official discovery by Delporte.
Wolf was a German astronomer and director of the influential Heidelberg Observatory, a prolific discoverer of minor planets and other astronomical objects himself. The asteroid was named by the discoverer based on a suggestion by Wolf's widow; the official naming citation was mentioned in The Names of the Minor Planets by Paul Herget in 1955. Asteroid 827 Wolfiana and the lunar crater Wolf were named in his honor. Asteroid Lightcurve Database, query form Dictionary of Minor Planet Names, Google books Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend Discovery Circumstances: Numbered Minor Planets - – Minor Planet Center 1217 Maximiliana at the JPL Small-Body Database Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters
The Amor asteroids are a group of near-Earth asteroids named after the archetype object 1221 Amor. The orbital perihelion of these objects is close to, but greater than, the orbital aphelion of Earth, with most Amors crossing the orbit of Mars; the Amor asteroid 433 Eros was the first asteroid to be orbited and landed upon by a robotic space probe. The orbital characteristics that define an asteroid as being in the Amor group are: The orbital period is greater than one year; as of 2019 there are 7427 known Amor asteroids. 1153 are numbered, 75 of them are named. An outer Earth-grazer asteroid is an asteroid, beyond Earth's orbit, but which can get closer to the Sun than Earth's aphelion, not closer than Earth's perihelion. Outer Earth-grazer asteroids are split between Apollo asteroids. Using the definition of Amor asteroids above, "Earth grazers" that never get closer to the Sun than Earth does are Amors, whereas those that do are Apollos. To be considered a hazardous asteroid, an object's orbit must, at some point, come within 0.05 AU of Earth's orbit, the object itself must be sufficiently large/massive to cause significant regional damage if it impacted Earth.
Most PHAs are either Aten asteroids or Apollo asteroids, but one tenth of PHAs are Amor asteroids. A hazardous Amor asteroid therefore must have a perihelion of less than 1.05 AU. 20% of the known Amors meet this requirement, about a fifth of those are PHAs. The fifty known Amor PHAs include the named objects 2061 Anza, 3122 Florence, 3908 Nyx, 3671 Dionysus; this is a non-static list of named Amor asteroids. Amor asteroid records Alinda family Arjuna asteroid List of minor planets List of Amor minor planets
Delporte is a lunar impact crater on the far side of the Moon. It overlies part of the northwestern rim of the huge walled plain Fermi, the crater Litke is nearly attached to the southeastern rim; the crater is named after Eugène Joseph Delporte. The rim of this crater is only marginally worn, although it is not quite circular and the edge is somewhat uneven. There is a shelf running along the northern inner wall. At the midpoint is a central ridge that extends to the northward. 1274 Delportia, minor planet