The Solar System is the gravitationally bound system of the Sun and the objects that orbit it, either directly or indirectly. Of the objects that orbit the Sun directly, the largest are the eight planets, with the remainder being smaller objects, such as the five dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly—the moons—two are larger than the smallest planet, Mercury.
Earth is the third planet from the Sun and the only astronomical object known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth orbits around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times.
The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention, and reducing temperature extremes between day and night.
The Shallow Sky Bulletin (ISSN 0897-2532) was published by Stephen M. Smith from 1986 through 2000. Mr. Smith operated The Comet Rapid Announcement Service (CRAS) to disseminate notices about newly discovered bright comets, news about comets and daily positions (ephemerides) for observable comets. The common practice for publishing comet tables was to display positions at 10-day intervals. All of the comet position tables published in SSB were at 1-day intervals. During the 14-year run of SSB, CRAS subscribers were informed about all observable comets.
In the 2006 April 13 issue of The Minor Planet Circulars/Minor Planets and Comets, published by The Minor Planet Center of the Smithsonian Astrophysical Observatory, Mr. Smith's work was honored by the naming of minor planet 9891 Stephensmith.
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Comet Hale–Bopp is a comet that was perhaps the most widely observed of the 20th century and one of the brightest seen for many decades.
Astronomy is the oldest of the natural sciences, dating back to antiquity, with its origins in the religious, mythological, cosmological, calendrical, and astrological beliefs and practices of prehistory: vestiges of these are still found in astrology, a discipline long interwoven with public and governmental astronomy. It was not completely separated in Europe during the Copernican Revolution starting in 1543. In some cultures, astronomical data was used for astrological prognostication. The study of astronomy has received financial and social support from many institutions, especially the Church, which was its largest source of support between the 12th century to the Enlightenment.
John Flamsteed FRS was an English astronomer and the first Astronomer Royal. His main achievements were the preparation of a 3,000-star catalogue, Catalogus Britannicus, and a star atlas called Atlas Coelestis, both published posthumously. He also made the first recorded observations of Uranus, although he mistakenly catalogued it as a star, and he laid the foundation stone for the Royal Greenwich Observatory.
In astronomy, a conjunction occurs when two astronomical objects or spacecraft have either the same right ascension or the same ecliptic longitude, usually as observed from Earth. The astronomical symbol for conjunction is ☌ and handwritten . The conjunction symbol is not used in modern astronomy. It continues to be used in astrology.
The orbital period is the time a given astronomical object takes to complete one orbit around another object, and applies in astronomy usually to planets or asteroids orbiting the Sun, moons orbiting planets, exoplanets orbiting other stars, or binary stars.
In astronomy and celestial navigation, an ephemeris gives the trajectory of naturally occurring astronomical objects as well as artificial satellites in the sky, i.e., the position over time. The etymology is from Latin ephemeris, meaning 'diary' and from Greek ἐφημερίς (ephemeris), meaning 'diary, journal'. 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 computed electronically, from mathematical models of the motion of astronomical objects and the Earth. However, printed ephemerides are still produced, as they are useful when computational devices are not available.
In ancient times, only the Sun and Moon, a few stars, and the most easily visible planets had names. Over the last few hundred years, the number of identified astronomical objects has risen from hundreds to over a billion, and more are discovered every year. Astronomers need to be able to assign systematic designations to unambiguously identify all of these objects, and at the same time give names to the most interesting objects and, where relevant, features of those objects.
The Minor Planet Center (MPC) is the official worldwide organization in charge of collecting observational data for minor planets, calculating their orbits and publishing this information via the Minor Planet Circulars. Under the auspices of the International Astronomical Union (IAU), it operates at the Smithsonian Astrophysical Observatory, which is part of the Center for Astrophysics along with the Harvard College Observatory.
In many cases astronomical phenomena viewed from the planet Mars are the same or similar to those seen from Earth but sometimes they can be quite different. For example, because the atmosphere of Mars does not contain an ozone layer, it is also possible to make UV observations from the surface of Mars.
Solar physics is the branch of astrophysics that specializes in the study of the Sun. It deals with detailed measurements that are possible only for our closest star. It intersects with many disciplines of pure physics, astrophysics, and computer science, including fluid dynamics, plasma physics including magnetohydrodynamics, seismology, particle physics, atomic physics, nuclear physics, stellar evolution, space physics, spectroscopy, radiative transfer, applied optics, signal processing, computer vision, computational physics, stellar physics and solar astronomy.
A lunar standstill is the gradually varying range between the northern and the southern limits of the Moon's declination, or the lunistices, over the course of one-half a sidereal month, or 13.66 days. One major, or one minor, lunar standstill occurs every 18.6 years due to the precessional cycle of the lunar nodes at that rate.
James Whitney Young is an American astronomer who worked in the field of asteroid research. After nearly 47 years with the Jet Propulsion Laboratory at their Table Mountain Facility, Young retired July 16, 2009.
The Association of Lunar and Planetary Observers is an international scientific and educational organization established in March, 1947 in the United States by Walter H. Haas, and later incorporated in 1990. ALPO is an organization for advancing and conducting astronomical work by both professional and amateur astronomers who share an interest in solar system observations. It is currently headquartered in Springfield, Illinois.
The Astronomical Almanac is an almanac published by the United States Naval Observatory (USNO) and Her Majesty's Nautical Almanac Office (HMNAO); it also includes data supplied by many scientists from around the world. It is considered a worldwide resource for fundamental astronomical data, often being the first publication to incorporate new International Astronomical Union resolutions. The almanac largely contains solar system ephemeris and catalogs of selected stellar and extragalactic objects. The material appears in sections, each section addressing a specific astronomical category. The book also includes references to the material, explanations, and examples. It is available one year in advance of its date.
Astronomical chronology, or astronomical dating, is a technical method of dating events or artifacts that are associated with astronomical phenomena. Written records of historical events that include descriptions of astronomical phenomena have done much to clarify the chronology of the Ancient Near East; works of art which depict the configuration of the stars and planets and buildings which are oriented to the rising and setting of celestial bodies at a particular time have all been dated through astronomical calculations.
A lost comet is one which was not detected during its most recent perihelion passage. This generally happens when data is insufficient to reliably calculate the comet's location or if the solar elongation is unfavorable near perihelion passage. The D/ designation is used for a periodic comet that no longer exists or is deemed to have disappeared.
C/2009 R1, one of more than fifty comets known as Comet McNaught, is a non-periodic comet discovered by British-Australian astronomer Robert H. McNaught on September 9, 2009, using the Uppsala Southern Schmidt Telescope at Siding Spring Observatory in New South Wales, Australia. The discovery was confirmed the same day at the Optical Ground Station telescope at Tenerife. After the discovery, earlier images of the comet were found from July 20, August 1, and August 18, 2009. It is believed C/2009 R1 will leave the Solar System permanently.
NightWatch: A Practical Guide to Viewing the Universe is a best-selling popular science book by Terence Dickinson. NightWatch is widely regarded as the essential guidebook for beginning stargazers. First published in 1983, there are over 800,000 copies in print, making it the top-selling stargazing guide in the world during the past 20 years. A fifth edition is expected in 2013. Each new edition has outsold the previous one because of revisions, updated material, star charts in particular, and new information on telescope and binocular technology. For the first time, the latest edition includes star charts for the Southern Hemisphere. There are also tables of future solar and lunar eclipses, planetary conjunctions and planet locations, all current to 2018. Over time, Dickinson has polished the book’s format and improved its usability based on his experience and comments from his colleagues, readers and fans.
Maya astronomy is the study of the Moon, planets, Milky Way, Sun, and other astronomical occurrences by the Precolumbian Maya Civilization of Mesoamerica. The Classic Maya in particular developed some of the most accurate pre-telescope astronomy in the world, aided by their fully developed writing system and their positional numeral system, both of which are fully indigenous to Mesoamerica. The Classic Maya understood many astronomical phenomena: for example, their estimate of the length of the synodic month was more accurate than Ptolemy's, and their calculation of the length of the tropical solar year was more accurate than that of the Spanish when the latter first arrived.
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