Eclipse in the context of Spectroscopic binary

An almanac (also spelled almanack and almanach) is a regularly published listing of a set of current information about one or multiple subjects. It includes information like weather forecasts, farmers' planting dates, tide tables, and other tabular data often arranged according to the calendar. Celestial figures and various statistics are found in almanacs, such as the rising and setting times of the Sun and Moon, dates of eclipses, hours of high and low tides, and religious festivals. The set of events noted in an almanac may be tailored for a specific group of readers, such as farmers, sailors, or astronomers.

Anaxagoras (/ˌænækˈsæɡərəs/; Ancient Greek: Ἀναξαγόρας, Anaxagóras, 'lord of the assembly'; c. 500 BC – c. 428 BC) was a Pre-Socratic Greek philosopher. Born in Clazomenae at a time when Asia Minor was under the control of the Persian Empire, Anaxagoras came to Athens. In later life he was charged with impiety and went into exile in Lampsacus.

Responding to the claims of Parmenides on the impossibility of change, Anaxagoras introduced the concept of Nous (Cosmic Mind) as an ordering force. He also gave several novel scientific accounts of natural phenomena, including the notion of panspermia, that life exists throughout the universe and could be distributed everywhere. He deduced a correct explanation for eclipses and described the Sun as a fiery mass larger than the Peloponnese, and also attempted to explain rainbows and meteors. He also speculated that the sun might be just another star.

The Antikythera mechanism (/ˌæntɪkɪˈθɪərə/ AN-tik-ih-THEER-ə, US also /ˌæntaɪkɪˈ-/ AN-ty-kih-) is an ancient Greek hand-powered orrery (model of the Solar System). It is the oldest known example of an analogue computer. It could be used to predict astronomical positions and eclipses decades in advance. It could also be used to track the four-year cycle of athletic games similar to an olympiad, the cycle of the ancient Olympic Games.

The artefact was among wreckage retrieved from a shipwreck off the coast of the Greek island Antikythera in 1901. In 1902, during a visit to the National Archaeological Museum in Athens, it was noticed by Greek politician Spyridon Stais as containing a gear, prompting the first study of the fragment by his cousin, Valerios Stais, the museum director. The device, housed in the remains of a wooden-framed case of (uncertain) overall size 34 cm × 18 cm × 9 cm (13.4 in × 7.1 in × 3.5 in), was found as one lump, later separated into three main fragments which are now divided into 82 separate fragments after conservation efforts. Four of these fragments contain gears, while inscriptions are found on many others. The largest gear is about 13 cm (5 in) in diameter and originally had 223 teeth. All these fragments of the mechanism are kept at the National Archaeological Museum, along with reconstructions and replicas, to demonstrate how it may have looked and worked.

An omen (also called portent) is a phenomenon that is believed to foretell the future, often signifying the advent of change. It was commonly believed in ancient history, and still believed by some today, that omens bring divine messages from the gods.

These omens include natural phenomena, for example an eclipse, abnormal births of animals (especially humans) and behaviour of the sacrificial lamb on its way to the slaughter. Specialists, known as diviners, variously existed to interpret these omens. They would also use an artificial method, for example, a clay model of a sheep liver, to communicate with their gods in times of crisis. They would expect a binary answer, either yes or no, favourable or unfavourable. They did these to predict what would happen in the future and to take action to avoid disaster.

The ecliptic or ecliptic plane is the orbital plane of Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making.

From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic against the background of stars – specifically the Zodiac constellations. The planets of the Solar System can also be seen along the ecliptic, because their orbital planes are very close to Earth's. The Moon's orbital plane is also similar to Earth's; the ecliptic is so named because the ancients noted that eclipses only occur when the Moon is crossing it.

The Canon of Kings was a dated list of kings used by ancient astronomers as a convenient means to date astronomical phenomena, such as eclipses. For a period, the Canon was preserved by the astronomer Claudius Ptolemy, and is thus known sometimes as Ptolemy's Canon. It is one of the most important bases for modern knowledge of ancient chronology.

The Canon derives originally from Babylonian sources. Thus, it lists Kings of Babylon from 747 BC until the conquest of Babylon by Achaemenid Persians in 539 BC, and then Persian kings from 538 to 332 BC. At this point, the Canon was continued by Greek astronomers in Alexandria, and lists the Macedonian kings from 331 to 305 BC, the Ptolemies from 304 BC to 30 BC, and the Roman and Byzantine Emperors, although they are not kings; in some manuscripts the list is continued down to the Fall of Constantinople in 1453.

In astronomy and celestial navigation, an ephemeris (/ɪˈfɛmərɪs/; pl. ephemerides /ˌɛfəˈmɛrɪˌdiːz/; from Latin ephemeris 'diary', from Ancient Greek ἐφημερίς (ephēmerís) 'diary, journal') is a book with tables that gives the trajectory of naturally occurring astronomical objects and artificial satellites in the sky, i.e., the position (and possibly velocity) over time. Historically, positions were given as printed tables of values, given at regular intervals of date and time. The calculation of these tables was one of the first applications of mechanical computers. Modern ephemerides are often provided in electronic form. However, printed ephemerides are still produced, as they are useful when computational devices are not available.

The astronomical position calculated from an ephemeris is often given in the spherical polar coordinate system of right ascension and declination, together with the distance from the origin if applicable. Some of the astronomical phenomena of interest to astronomers are eclipses, apparent retrograde motion/planetary stations, planetary ingresses, sidereal time, positions for the mean and true nodes of the moon, the phases of the Moon, and the positions of minor celestial bodies such as Chiron.

A binary star or binary star system 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 as separate stars using a telescope, 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 each other's outer stellar atmospheres. In some cases, these close binary systems can exchange mass, which may bring their evolution to stages that single stars cannot attain. Examples of binaries are Sirius and Cygnus X-1 (Cygnus X-1 being a well-known black hole). Binary stars are also common as the nuclei of many planetary nebulae, and are the progenitors of both novae and type Ia supernovae.

An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks from view (occults) an object in the background. In this general sense, occultation applies to the visual scene observed from low-flying aircraft (or computer-generated imagery) when foreground objects obscure distant objects dynamically, as the scene changes over time.

If the closer body does not entirely conceal the farther one, the event is called a transit. Both transit and occultation may be referred to generally as occlusion; and if a shadow is cast onto the observer, it is called an eclipse.

In astronomy, a transit (or astronomical transit) is the passage of a celestial body directly between a larger body and the observer. As viewed from a particular vantage point, the transiting body appears to move across the face of the larger body, covering a small portion of it.

The word "transit" refers to cases where the nearer object appears smaller than the more distant object. Cases where the nearer object appears larger and completely hides the more distant object are known as occultations.

Astronomical events are celestial body events such as eclipses, novae or planetary collisions studied by the scientific discipline of astronomy, whereas "astronomy events" refers to social events such as academic meetings, conferences and other such newsworthy occasions relating to astronomy.

In astronomy, a syzygy (/ˈsɪzədʒi/ SIZ-ə-jee; from Ancient Greek συζυγία (suzugía) 'union, yoking', expressing the sense of σύν (syn- "together") and ζυγ- (zug- "a yoke")) is a roughly straight-line configuration of three or more celestial bodies in a gravitational system.

The word is often used in reference to the Sun, Earth, and either the Moon or a planet, where the latter is in conjunction or opposition. Solar and lunar eclipses occur at times of syzygy, as do transits and occultations.

A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season in its new moon phase, when the Moon's orbital plane is closest to the plane of Earth's orbit. In a total eclipse, the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses, only part of the Sun is obscured. Unlike a lunar eclipse, which may be viewed from anywhere on the night side of Earth, a solar eclipse can only be viewed from a relatively small area of the world. As such, although total solar eclipses occur somewhere on Earth every 18 months on average, they recur at any given place only once every 360 to 410 years.

If the Moon were in a perfectly circular orbit and in the same orbital plane as Earth, there would be total solar eclipses at every new moon. Instead, because the Moon's orbit is tilted at about 5 degrees to Earth's orbit, its shadow usually misses Earth. Solar (and lunar) eclipses therefore happen only during eclipse seasons, resulting in at least two, and up to five, solar eclipses each year, no more than two of which can be total. Total eclipses are rarer because they require a more precise alignment between the centers of the Sun and Moon, and because the Moon's apparent size in the sky is sometimes too small to fully cover the Sun.