"a healthy heart, the main pacemaker is a collection of cells on the border of the atria and vena cava called the sinoatrial node. Heart cells exhibit automaticity which is the ability to generate electrical activity independent of external stimulation. As a result, the cells of the node spontaneously generate electrical activity that is subsequently conducted throughout the heart, resulting in a regular heart rate. In absence of any external stimuli, sinoatrial pacing contributes to maintain the heart rate in the range of 60-100 beats per minute (bpm). At the same time, the two branches of the autonomic nervous system"
"Sinus Sabaeus quadrangle The Sinus Sabaeus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. It is also referred to as MC-20 (Mars Chart-20). The Sinus Sabaeus quadrangle covers the area from 315° to 360° west longitude and 0° to 30° degrees south latitude on Mars. It contains Schiaparelli, a large, easily visible crater that sits close to the equator. The Sinus Sabaeus quadrangle contains parts of Noachis Terra and Terra Sabaea. The name comes from an incense-rich location south of the Arabian peninsula (the Gulf"
"semi-major axis of 3.42 AU). Its orbit has an eccentricity of 0.31 and an inclination of 39° with respect to the ecliptic. The body's observation arc begins with its official discovery observation at Mount Wilson in August 1935. ""Cincinnati"", a non-family asteroid of the main belt's background population, is located in the orbital region of the Cybele asteroid, the last outpost of an extended asteroid belt beyond the Hecuba-gap asteroids. Due to its high inclination, and contrary to all other Cybele asteroids, ""Cincinnati"" is the only one that is above the center of the ν secular resonance with Saturn. The"
"Sinus Fidei Sinus Fidei (Latin for ""Bay of Faith"") is a small basaltic mare feature in the Terra Nivium region of the Moon. It is also located more than 45 km west of the prominent Yangel' crater. The bay lies northwest of Mare Vaporum which is narrowly linked, a small lies in the middle of that area. Northeast is the rille known as Rima Conon which runs partly in a zig-zag form. Its crater is located north of the bay. Outside the bay, hills dominate the land shore especially to the east, in that location is Conon W, further east"
"is found to correspond to a longitude midway between the Nile and the end of the Euphrates. The modern molad moments match the mean solar times of the lunar conjunction moments near the meridian of Kandahar, Afghanistan, more than 30° east of Jerusalem. Furthermore, the discrepancy between the molad interval and the mean synodic month is accumulating at an accelerating rate, since the mean synodic month is progressively shortening due to gravitational tidal effects. Measured on a strictly uniform time scale, such as that provided by an atomic clock, the mean synodic month is becoming gradually longer, but since the"
"Nilo Syrtis Nilo Syrtis (or Nilosyrtis) is a region just north of Syrtis Major Planum on Mars, at approximately 23°N, 76°E and an elevation of −0.5 km. It marks a region of transition (a ""crustal dichotomy"") between southern highland and northern lowland terrain, and consists of isolated peaks and mesas. On average, the drop in elevation between the two terrains is 5,500 meters (18,000 feet). Nilosyrtis is one of the sites proposed as a landing site for the Mars Science Laboratory. However, it did not make the final cut. It was in the top 7, but not in the top"
"Red Spider Nebula The Red Spider Nebula (also catalogued as ""NGC 6537"") is a planetary nebula located near the heart of the Milky Way, in the northwest of the constellation Sagittarius. The nebula has a prominent two-lobed shape, possibly due to a binary companion or magnetic fields and has an ‘S’-shaped symmetry of the lobes – the lobes opposite each other appear similar. This is believed to be due to the presence of a companion to the central white dwarf. However, the gas walls of the two lobed structures are not at all smooth, but rather are rippled in a"
"the present day Rye. The rocks underlying Arthur's Seat are Dromana granite, and the granite is bounded to the west by the Selwyn Fault. Anthonys Nose (Victoria) Anthonys Nose is a point, or escarpment located on the southern shore of Port Phillip Bay, between Dromana and McCrae, in Victoria, Australia. It was named by Charles La Trobe, who became the Superintendent of the Port Phillip District of New South Wales in 1839. He thought that the landform had a strong resemblance to Anthony's Nose (Westchester) on the Hudson River, New York. In the early years of the European settlement of"
"Sinus Amoris Sinus Amoris (Latin for ""Bay of Love"") extends northward from the northeast end of the Mare Tranquillitatis. It is located at selenographic coordinates 18.1° N, 39.1° E, and lies within a diameter of 130 km. To the north of the bay are the jumbled Montes Taurus peaks. Near the southern end of the bay where it outlets into the Mare Tranquillitatis lies the crater Theophrastus. Along the western side is the flooded crater Maraldi and Mons Maraldi. Bordering the east side of the bay are the craters Carmichael and Hill. There are some low ridges in the central"
"assumed that he recorded the position incorrectly, and the New General Catalogue gives Rosse's object as the other knot in the northern cloud, located at J2000 RA Dec , one degree north of Rosse's position. (This position is farther east than NGC 6979, even though NGC objects are generally ordered by increasing RA.) These filaments in the north-central area are sometimes known as the ""carrot"". The spectrum at 34.5 MHz of the region associated with NGC 6974 ranges straight over the entire frequency range 25 to 5000 MHz. The southeastern knot is located at J2000 RA Dec on the southeastern"
"is the flooded crater Stadius and the Mare Insularum to the southwest. Sinus Aestuum Sinus Aestuum (Latin for ""Seething Bay"") forms a northeastern extension to Mare Insularum. It is centered at selenographic coordinates 12.1° N, 8.3° W, and it lies within a diameter of about 320 km. The Sinus Aestuum is a level, nearly featureless surface of low albedo basaltic lava that is marked by a few small impacts and some wrinkle ridges. The eastern border is formed by an area of irregular terrain that divides the bay from the Mare Vaporum to the east. To the north is the"
"Nobile (crater) Nobile is a lunar impact crater that is located near the southern pole of the Moon. It lies to the south of the crater Scott, along the western rim of Amundsen. Between Nobile and the southern pole lie the smaller craters Shoemaker and Faustini. This is an eroded crater formation that is almost constantly cloaked in deep shadows. When sunlight does enter the interior of this crater, it does so at a very oblique angle. The crater rim is overlaid by several lesser craters, the most notable being a formation about half the diameter of Nobile along the"
"Sinus Asperitatis Sinus Asperitatis (Latin for ""Bay of Roughness"") is an area of lunar mare that extends southward from the Mare Tranquillitatis until it joins the Mare Nectaris to the southeast. It is bordered along the western and eastern sides by continental regions of irregular terrain. The selenographic coordinates of this feature are 3.8° S, 27.4° E, and it has a diameter of 206 km. In the northern part of this mare is the small crater Torricelli. At the southern end is the prominent crater pair of Theophilus and Cyrillus. On the border between Sinus Asperitatis and the Mare Nectaris"
"Anthonys Nose (Victoria) Anthonys Nose is a point, or escarpment located on the southern shore of Port Phillip Bay, between Dromana and McCrae, in Victoria, Australia. It was named by Charles La Trobe, who became the Superintendent of the Port Phillip District of New South Wales in 1839. He thought that the landform had a strong resemblance to Anthony's Nose (Westchester) on the Hudson River, New York. In the early years of the European settlement of Dromana there were geographical obstacles to travelling by land. A journey from Melbourne to the area meant crossing swamps and streams. Anthony's Nose was"
"America except for Guyaranquil, New Granada (now in Ecuador) and around it and the southern tip, Florida (then also as Spanish Florida) and the Caribbean, the Atlantic, much of Africa except for the Ottoman lands of a part of Tunis including Philippeville (now Bizerte) and Carthage, Cyrenaica, Egypt and East Nubia as well as the Somali Peninsula and much of Spain and Portugal except for the Pyrenees. It was also visible in a small part of the Indian Ocean and hundreds of miles (or kilometers) offshore from Antarctica. It was part of solar saros 132. The umbral portion which was"
"Project Apollo. Arthur C. Clarke's novel ""A Fall of Moondust"" is set in a fictional ""Sea of Thirst"" located within Sinus Roris. Sinus Roris Sinus Roris (Latin for ""Bay of Dew"") is an extension of the northern edge of Oceanus Procellarum on the Moon. The IAU-defined selenographic coordinates of this bay are 54.0° N, 56.6° W, and the diameter is 202 km. The borders of this feature are somewhat indistinct. The bay proper is framed along the western edge by the craters Markov and Oenopides, and to the north by Babbage and South. At the eastern edge it joins the"
"Eta Sagittarii Eta Sagittarii (Eta Sgr, η Sagittarii, η Sgr) is a binary star system in the southern zodiac constellation of Sagittarius. Based upon parallax measurements, it is located at a distance of from Earth. It was formerly known as ""Beta Telescopii"" (β Tel). In India, where part of the constellation of Sagittarius represents an Elephant, this star forms the creature's tail. The primary component, η Sagittarii A, is a red giant star with a stellar classification of M2 III. It is an evolved star that is currently at a stage called the asymptotic giant branch, having exhausted both the"
"is the crater Mädler. Sinus Asperitatis Sinus Asperitatis (Latin for ""Bay of Roughness"") is an area of lunar mare that extends southward from the Mare Tranquillitatis until it joins the Mare Nectaris to the southeast. It is bordered along the western and eastern sides by continental regions of irregular terrain. The selenographic coordinates of this feature are 3.8° S, 27.4° E, and it has a diameter of 206 km. In the northern part of this mare is the small crater Torricelli. At the southern end is the prominent crater pair of Theophilus and Cyrillus. On the border between Sinus Asperitatis"
"AU once every 103 years and 2 months (37,683 days; semi-major axis of 22.0 AU). Its orbit has an eccentricity of 0.46 and an inclination of 36° with respect to the ecliptic. The body's observation arc begins with its official discovery observation at Apache Point in September 2006. In 2010, thermal flux from in the far-infrared was measured by the Herschel Space Telescope. As a result, its equivalent size was estimated to lie within a range from to . (248835) 2006 SX368 , provisional designation , is a centaur orbiting in the outer Solar System between Saturn and Neptune, approximately"
"Sinus Aestuum Sinus Aestuum (Latin for ""Seething Bay"") forms a northeastern extension to Mare Insularum. It is centered at selenographic coordinates 12.1° N, 8.3° W, and it lies within a diameter of about 320 km. The Sinus Aestuum is a level, nearly featureless surface of low albedo basaltic lava that is marked by a few small impacts and some wrinkle ridges. The eastern border is formed by an area of irregular terrain that divides the bay from the Mare Vaporum to the east. To the north is the Montes Apenninus range and the prominent crater Eratosthenes. Along the western side"
"Sinus Iridum Sinus Iridum (Latin for ""Bay of Rainbows"") is a plain of basaltic lava that forms a northwestern extension to the Mare Imbrium on Earth's moon. It is surrounded from the northeast to the southwest by the Montes Jura range. Close to the bay in the range in the northwest is the crater Bianchini; west of the bay is the crater Sharp. The protruding part of the range at the southwest end is named Promontorium Heraclides, while that at the northeast end is called Promontorium Laplace. This bay and the surrounding mountains is considered one of the most beautiful"
"it was located at the very center of our Galaxy, despite being some 32 degrees south-west of the conjectured galactic center of the time. In 1958 the International Astronomical Union (IAU) decided to adopt the position of Sagittarius A as the true zero co-ordinate point for the system of galactic latitude and longitude. In the equatorial coordinate system the location is: RA , Dec (J2000 epoch). The exact distance between the Solar System and the Galactic Center is not certain, although estimates since 2000 have remained within the range . The latest estimates from geometric-based methods and standard candles yield"
"visible from a narrow corridor beginning in the south Atlantic Ocean and sweeping eastward 900 km south of Africa, slowly curving northeast through the Indian Ocean. Its first landfall was in the Cocos Islands followed by southern Sumatra and western Java. It continued somewhat more easterly across central Borneo, across the northwestern edge of Celebes, then ending just before Mindanao, Philippines. The border of Sarawak, Malaysia in southeast part of Kapit Division nearly missed the annular line. <BR>Animated path Photos: Solar eclipse of January 26, 2009 An annular solar eclipse occurred on January 26, 2009. A solar eclipse occurs when"
"Lyot (lunar crater) Lyot is a large lunar impact crater that is located along the southeastern limb of the Moon. It lies within the irregular and patchy lunar mare named Mare Australe, and to the south of the crater Hamilton. Due to its location, this formation is viewed at a low angle from the Earth, and its visibility is affected by libration. The interior floor of this crater has been resurfaced by lava, leaving a dark interior with an albedo that matches the surrounding mare. The outer rim is low and heavily worn, with a perimeter that forms a somewhat"
"basin of Nectarian age. Pilâtre (crater) Pilâtre is a lunar impact crater near the southwestern limb of the Moon. It is located just to the north-northwest of the much larger walled plain Hausen. The satellite crater Pingré S is attached to the eastern rim, with Pingré itself located farther to the northeast. Just to the west-southwest is Chappe, a formation of similar dimension to Pilâtre. Due to its location, this crater is viewed almost from the edge from the Earth, limiting the amount of detail that can be observed. This part of the surface is also subject to libration, and"
"of a central crossbar and bulge from which two major and several minor spiral arms radiate outwards. The Carina–Sagittarius Arm lies between two major spiral arms—the Scutum–Centaurus Arm the near part of which is visible looking ""inward"" i.e. toward the galactic centre with the rest beyond the galactic centre and the Perseus Arm, similar in size and shape but locally positioned outward. It is named for its proximity to the Sagittarius and Carina constellations as seen in the night sky from Earth, in the direction of the galactic center. The arm dissipates near its middle, shortly after reaching its maximal"
"Arabic النياط ""an-niyāţ"" meaning ""the arteries (of the scorpion)"" and referring to their position flanking the star Antares, the scorpion's heart. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name ""Alniyat"" for the component Sigma Scorpii Aa1 on February 1, 2017 and it is now so included in the List of IAU-approved Star Names. In Chinese, (), meaning ""Heart"", refers to an asterism consisting of Sigma Scorpii, Antares"
"Lambda Sagittarii Lambda Sagittarii (λ Sagittarii, abbreviated Lambda Sgr, λ Sgr), also named Kaus Borealis, is a star in the southern constellation of Sagittarius. The star marks the top of the Archer's bow. With an apparent visual magnitude of +2.82, this is one of the brighter members of the constellation and, according to the Bortle Dark-Sky Scale, it is readily visible to the naked eye. Based upon parallax measurements, it is from the Sun. Being 2.1 degrees south of the ecliptic, Lambda Sgr is sometimes occulted by the Moon and, rarely, by a planet. The last planet to pass in"
"Knobel (crater) Knobel is an impact crater in the Mare Tyrrhenum quadrangle of Mars, located at 6.7°S latitude and 226.8°W longitude and is in the northern end of Terra Cimmeria. It is 128.6 kilometers in diameter and was named after Edward Knobel, and the name was approved in 1973 by the International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (WGPSN). Nearby named craters include Herschel to the west-northwest, Gale to the east-northeast, the Lasswitz-Wien crater pair to the southeast and nearly meets with Robert Sharp to the north. A smaller crater lies southeast of Knobel with an almost"
"Gamma2 Sagittarii Gamma² Sagittarii (γ² Sagittarii, abbreviated Gamma² Sgr, γ² Sgr), also named Alnasl, is a 3rd-magnitude star in the zodiac constellation of Sagittarius. The location of this star forms the tip of the arrow in the bow of Sagittarius the Centaur. Based on parallax measurements obtained during the Hipparcos mission, it is approximately from the Sun. It has an apparent visual magnitude of +2.98, making it the seventh-brightest star in the constellation. It forms part of a double star along with a fainter optical companion designated Gamma¹ Sagittarii located about 50 arcminutes north of this star. The latter is"
"Sinus Medii Sinus Medii (""Central Bay"") is a small lunar mare. It takes its name from its location at the intersection of the Moon's equator and prime meridian; as seen from the Earth, this feature is located in the central part of the Moon's near side, and it is the point closest to the Earth. From this spot the Earth would always appear directly overhead, although the planet's position would vary slightly due to libration. During the Apollo program, Sinus Medii was desingated ALS3. Flight operations planners were concerned about having the optimum lighting conditions at the landing site, hence"
"Amphidromic point An amphidromic point, also called a tidal node, is a point of zero amplitude of one harmonic constituent of the tide. The tidal range (the peak-to-peak amplitude, or height difference between high tide and low tide) for that harmonic constituent increases with distance from this point. The term ""amphidromic point"" derives from the Greek words ""amphi"" (around) and ""dromos"" (running), referring to the rotary tides running around them. Amphidromic points occur because the Coriolis effect and interference within oceanic basins, seas and bays creates a wave pattern — called an amphidromic system — which rotates around the amphidromic"
"each month is shown in black, and the solstices and equinoxes are shown in green. It can be seen that the equinoxes occur approximately at altitude , and the solstices occur approximately at altitudes where ""ε ""is the axial tilt of the earth, 23.4°. The analemma is plotted with its width highly exaggerated, revealing a slight asymmetry (due to the two-week misalignment between the apsides of the Earth's orbit and its solstices). The analemma is oriented with the smaller loop appearing north of the larger loop. At the North Pole, the analemma would be completely upright (an 8 with the"