Fact-checked by Grok 2 weeks ago

Northern celestial hemisphere

The northern celestial hemisphere is the northern half of the celestial sphere, defined as the region north of the celestial equator, which is the projection of Earth's equator onto the imaginary sphere surrounding our planet. This hemisphere includes all celestial objects with declinations ranging from 0° to +90°, where declination measures angular distance north or south of the celestial equator, and it is primarily visible to observers located in Earth's northern hemisphere. From the North Pole, the entire northern celestial hemisphere remains above the horizon, while its visibility decreases toward the equator, where both hemispheres become accessible over a full day and night cycle.^[1]^[2]^[3] At the center of this hemisphere lies the north celestial pole, the point on the celestial sphere directly above Earth's North Pole, around which all stars appear to rotate due to Earth's daily rotation; the star Polaris (Alpha Ursae Minoris) lies within about 1° of this pole, serving as a reliable navigational reference for northern observers.^[4]^[5] The hemisphere features several circumpolar constellations—groups of stars that never set below the horizon for northern latitudes—including Ursa Major (the Great Bear, home to the prominent Big Dipper asterism), Ursa Minor (the Little Bear, containing Polaris), Cassiopeia (the Queen, forming a distinctive W shape), Draco (the Dragon), and Cepheus (the King). These constellations are visible year-round from mid-northern latitudes, providing consistent celestial markers.^[6]^[3] Seasonally, the northern celestial hemisphere showcases a variety of prominent constellations and bright stars. In spring, observers can spot Bootes (with the bright star Arcturus), Leo (featuring Regulus), and Virgo (including Spica); summer brings Cygnus (the Swan, with Deneb), Lyra (home to Vega), and Aquila (with Altair), forming part of the prominent Summer Triangle asterism; autumn highlights Andromeda (containing the Andromeda Galaxy, the nearest major galaxy to the Milky Way), Pegasus, and Perseus (with the variable star Algol); and winter reveals Orion (the Hunter, boasting Betelgeuse and Rigel), Taurus (with Aldebaran and the Pleiades cluster), and Gemini (Castor and Pollux). These patterns, formalized into 36 official northern constellations by the International Astronomical Union, have been used for navigation, timekeeping, and mythology across cultures for millennia.^[3]^[7]^[8] The northern celestial hemisphere also hosts significant astronomical phenomena and objects, such as the aurora borealis near the poles, numerous galaxies like M31 in Andromeda, and variable stars used in distance measurements; its study forms the basis of northern sky atlases and contributes to understanding stellar motions and cosmology.^[3]^[1]

Definition and Geometry

Celestial Equator and Division

The celestial equator is the great circle on the celestial sphere that represents the projection of Earth's equator onto the imaginary sphere surrounding the planet, lying in the same plane and equidistant from the celestial poles.^[9] This equator divides the celestial sphere into two equal hemispheres: the northern celestial hemisphere, which lies above the equator, and the southern celestial hemisphere, below it.^[9] The northern celestial hemisphere encompasses all points on the celestial sphere with positive declination, ranging from 0° at the equator to +90° at the north celestial pole.^[9] It covers exactly 50% of the celestial sphere's total surface area, as the equator forms a great circle that bisects the sphere symmetrically. The north celestial pole, located at +90° declination, serves as the anchor point for this hemisphere, while the south celestial pole at -90° declination anchors the southern counterpart.^[9] Geometrically, the northern celestial hemisphere aligns with Earth's northern polar region, becoming fully visible from the North Pole, where observers see the entire hemisphere rotating around the overhead north celestial pole without any stars setting.^[10] From latitudes north of the equator, such as mid-northern locations, a significant portion remains visible, though the exact observable area diminishes as one moves southward toward the equator, where the celestial equator passes directly overhead and half the northern hemisphere is accessible over the course of a year.^[10] Further south, visibility decreases progressively, with less of the northern hemisphere accessible due to the horizon's obstruction.^[10] Within this hemispherical division, equatorial coordinate systems employ declination to precisely locate celestial objects, measuring angular distance north or south of the celestial equator.^[9]

Coordinate Systems

The equatorial coordinate system serves as the fundamental framework for locating objects in the northern celestial hemisphere, analogous to latitude and longitude on Earth. It employs two angular coordinates: right ascension (RA) and declination (Dec). Right ascension measures the eastward angular distance along the celestial equator from a reference point, expressed either in hours, minutes, and seconds (ranging from 0h to 24h, where 24h = 360°) or in degrees (0° to 360°), with each hour corresponding to 15° of arc. Declination, in contrast, quantifies the north-south position relative to the celestial equator, measured in degrees from 0° at the equator to +90° at the north celestial pole for objects in the northern hemisphere.^[9] The vernal equinox defines the origin for right ascension, marking the point where the ecliptic—the apparent path of the Sun—intersects the celestial equator moving northward, typically around March 20-21 in the Gregorian calendar. This intersection provides a fixed, seasonally recurring reference aligned with Earth's orbit, ensuring consistent positioning independent of the observer's location. For instance, Polaris (α Ursae Minoris), a prominent star near the north celestial pole, has coordinates of approximately RA 2h 31m and Dec +89° 16', illustrating how high declination values place objects close to the pole and visible year-round from northern latitudes.^[9]^[11] While the horizon coordinate system—using altitude (angular height above the local horizon, from 0° to 90°) and azimuth (horizontal direction clockwise from true north, from 0° to 360°)—offers practical orientation for northern observers by relating sky positions to the ground, it varies with the observer's latitude and time due to Earth's rotation. The equatorial system's universality, however, makes it ideal for global cataloging and long-term astronomical records, as positions remain fixed relative to the distant stars. From northern Earth latitudes, this system facilitates the identification of circumpolar objects with declinations greater than 90° minus the latitude.^[9]^[12] In modern astronomy, the International Celestial Reference System (ICRS) realizes the equatorial coordinates with high precision, defined by the positions of over 200 quasars and other extragalactic radio sources to form a quasi-inertial frame aligned with the mean equator and equinox at the J2000.0 epoch (January 1, 2000). This system ensures stability against precession and nutation effects, supporting accurate measurements for space missions and deep-sky surveys.^[13]

Astronomical Contents

Constellations

The northern celestial hemisphere contains 36 constellations that lie principally north of the celestial equator, as defined by the boundaries established by the International Astronomical Union (IAU). These include prominent patterns such as Ursa Major (the Great Bear), Cassiopeia (the Queen), Draco (the Dragon), Andromeda (the Princess), Pegasus (the Winged Horse), Auriga (the Charioteer), Cepheus (the King), Cygnus (the Swan), Lyra (the Lyre), and Hercules (the Hero), among others like Aries, Cancer, Coma Berenices, Corona Borealis, Delphinus, Equuleus, Lacerta, Leo Minor, Lynx, Perseus, Sagitta, Triangulum, Ursa Minor, Vulpecula, Boötes, Camelopardalis, Canes Venatici, and others totaling 36.^[14] In addition, 15 IAU constellations straddle the celestial equator, with several of them appearing predominantly in the northern hemisphere due to the majority of their area lying north of declination 0°, such as Aquila (the Eagle), Canis Minor (the Little Dog), Leo (the Lion), Orion (the Hunter), Pisces (the Fish), Serpens (the Serpent), and Taurus (the Bull). This brings the total to 43 constellations that are wholly or predominantly northern out of the 88 IAU-recognized ones. The boundaries for all 88 constellations were delineated by Belgian astronomer Eugène Delporte and approved by the IAU at its 1928 General Assembly, using arcs of right ascension and parallels of declination for precise division of the celestial sphere, with northern examples like Ursa Major extending across high declinations from approximately +29° to +73°.^[15]^[16]^[17]^[18] A subset of these northern constellations are circumpolar, remaining visible throughout the year from mid-northern latitudes (above about 40° N) without setting below the horizon; key examples include Ursa Minor (the Little Bear), Cepheus, Cassiopeia, Draco, and Camelopardalis (the Giraffe). These circumpolar patterns rotate around the north celestial pole and provide a constant reference for observers in the northern hemisphere.

Stars and Deep-Sky Objects

The northern celestial hemisphere features a rich array of prominent stars, including many of the brightest visible from Earth. Arcturus (Alpha Boötis), the brightest star north of the celestial equator, is a red giant with an apparent visual magnitude of -0.05 and a declination of +19°10'56". Located approximately 37 light-years away, it shines with an orange hue due to its K0 III spectral type.^[19] Polaris (Alpha Ursae Minoris), serving as the current north pole star, has a declination of +89°15'51" and an apparent magnitude averaging 2.02, making it a key reference for celestial navigation; it is a classical Cepheid variable of spectral type F7 Ib.^[20] Vega (Alpha Lyrae), a prominent A0V main-sequence star at magnitude 0.03 and declination +38°47'01", lies about 25 light-years distant and marks the summer sky as part of the Summer Triangle asterism.^[21] Other notable bright stars include Capella (Alpha Aurigae), a spectroscopic binary system of G3 III and G8 III types with combined magnitude 0.08 at declination +45°59'53", situated 43 light-years away and appearing as a golden-yellow point of light.^[22] Altair (Alpha Aquilae), a rapidly rotating A7 V star of magnitude 0.76 and declination +08°52'06", is just 17 light-years distant, making it one of the closest bright stars and a vertex of the Summer Triangle.^[23] Together, these and similar luminaries—such as those in constellations like Bootes, Ursa Minor, Lyra, Auriga, and Aquila—account for the majority of the 25 brightest stars observable from Earth, highlighting the hemisphere's dominance in stellar brilliance.^[24] Among deep-sky objects, the northern hemisphere boasts striking examples of galaxies, clusters, and nebulae. The Andromeda Galaxy (M31), the closest major spiral galaxy to the Milky Way, lies approximately 2.5 million light-years away in the constellation Andromeda and is visible to the naked eye under dark skies as a faint, elongated patch.^[25] The Pleiades (M45), an open star cluster in Taurus about 400 light-years distant, contains over 1,000 young, hot B-type stars loosely bound by gravity and is renowned for its hazy appearance to the unaided eye, evoking the "Seven Sisters."^[26] The Orion Nebula (M42), a vast stellar nursery straddling the celestial equator but prominently viewed from northern latitudes, is located 1,500 light-years away with an apparent magnitude of 4, revealing intricate gas clouds and star formation when observed through binoculars or telescopes.^[27] Globular clusters like M13 in Hercules, one of the brightest such objects at magnitude 5.8 and 25,000 light-years distant, comprise hundreds of thousands of ancient stars in a dense, spherical swarm spanning about 145 light-years.^[28] Similarly, the Ring Nebula (M57) in Lyra, a planetary nebula 2,000 light-years away, exhibits a classic smoke-ring structure formed by the ejected outer layers of a dying Sun-like star, with the central white dwarf illuminating the glowing shell.^[29] These objects, observable within their respective northern constellations, exemplify the diversity of stellar evolution and interstellar phenomena in this sky region.

Observation from Earth

Visibility and Seasonal Changes

The visibility of the northern celestial hemisphere varies significantly with the observer's latitude on Earth. At the North Pole, the entire northern celestial hemisphere remains above the horizon at all times, providing 100% visibility year-round as the celestial equator lies directly on the horizon.^[10] As the observer moves southward, the visible portion decreases; at mid-northern latitudes, such as 40°N, a portion of the northern hemisphere is circumpolar (always above the horizon), while the rest rises and sets but remains fully accessible over a full night, with parts dipping below the horizon at times. By the equator, visibility reduces to about 50%, as only half the sky is above the horizon at any moment, though the full northern hemisphere can be observed over the course of a sidereal day.^[30] Certain stars and constellations within the northern celestial hemisphere become circumpolar—never setting below the horizon—for observers whose latitude exceeds 90° minus the object's declination. For instance, Polaris, with a declination of approximately +89.3°, is circumpolar for latitudes greater than about 1°N, remaining visible throughout the night and serving as a key reference for northern orientation.^[31] This creates a rotating ring of circumpolar objects around the north celestial pole, whose altitude equals the observer's latitude.^[32] Seasonal changes in visibility arise from Earth's orbit around the Sun, shifting which portions of the northern celestial hemisphere dominate the evening sky. In winter for northern observers, constellations like Orion and Taurus rise prominently in the east after sunset, reaching high altitudes by midnight and offering clear views of the hemisphere's brighter regions. During summer, Cygnus and Lyra take prominence overhead in the evening, tracing the Milky Way's path across the northern sky. At the equinoxes, the view balances both hemispheres equally, with the celestial equator aligned such that roughly equal portions of northern and southern skies are visible during the night.^[33]^[34]^[35] Earth's axial tilt of 23.5° relative to its orbital plane causes these seasonal shifts by varying the Sun's declination between +23.5° and -23.5°, which determines the opposite nighttime sky.^[36]^[37] Daily motion of the northern celestial hemisphere results from Earth's rotation, appearing as a westward progression around the north celestial pole over a sidereal day of 23 hours 56 minutes 4 seconds, slightly shorter than the solar day of 24 hours due to Earth's orbital motion advancing the Sun's position by about 1° eastward daily.^[38] This difference accumulates to one extra sidereal day per year, ensuring the stars return to the same sky position relative to the observer every 365.25 sidereal days.^[39] Polaris, located at the end of the Little Dipper's handle in Ursa Minor, has long served as the primary north indicator for navigators in the northern hemisphere. Its altitude above the horizon closely approximates the observer's latitude, enabling straightforward determination of position relative to the equator without complex instruments. This method relies on the star's proximity to the north celestial pole, historically within 1° of true north, which provided sufficient accuracy for ancient and early modern wayfinding.^[40]^[41]^[42] To locate Polaris, observers frequently employ the Big Dipper asterism within the constellation Ursa Major as a guide. The two outermost stars in the Big Dipper's bowl, known as the pointer stars, form an imaginary line that, when extended roughly five times their separation distance, points directly to Polaris. This technique, rooted in practical stellar navigation, allows reliable identification of the north direction even in unfamiliar skies.^[43] Due to the 26,000-year cycle of Earth's axial precession, other stars have periodically assumed the role of pole star. Kochab, or Beta Ursae Minoris, functioned as a prominent northern indicator from approximately 1700 BCE to 300 CE, circling the celestial pole closely enough to serve as a navigational reference during ancient Mediterranean and Near Eastern voyages. Its position made it a "guardian of the pole" alongside nearby Pherkad, offering dual markers for orientation in eras before Polaris dominated.^[44]^[45] Beyond directional guidance, certain northern stars facilitated timekeeping and seasonal navigation for agricultural and maritime purposes. In ancient Greece, Hesiod's Works and Days (circa 700 BCE) described the acronycal rising of Arcturus in Boötes as a spring signal for pruning vines and initiating planting activities, encapsulated in the enduring mnemonic "Arcturus in the spring." Complementing this, Spica in Virgo marked key harvest periods through its heliacal risings and settings, helping coordinate planting cycles in Boeotia around the 8th century BCE and tracing back to Neolithic associations with cereal cultivation.^[46]^[47] Vega in Lyra also played a role in ancient alignments tied to the summer solstice. Prehistoric structures at Nabta Playa in Egypt, dating to around 6270 BCE, featured orientations linking Vega's position to solstice events, aiding early pastoralists in tracking seasonal migrations and water resources through celestial navigation. These stars' patterns become prominent during their respective seasonal visibilities, reinforcing their practical value for northern observers.

Historical and Cultural Aspects

Development in Ancient Astronomy

The study of the northern celestial hemisphere in ancient astronomy began with Babylonian observations around the 2nd millennium BCE, where astronomers identified constellations such as MUL.MUL (the Pleiades) and the Bull of Heaven (likely Taurus) in the northern skies to track seasonal changes and divine omens through cuneiform records.^[48] These early mappings, preserved in texts like the MUL.APIN compendium from circa 1000 BCE, laid foundational patterns that emphasized northern circumpolar stars for reliable timekeeping in agriculture and navigation. Greek astronomers built upon Babylonian traditions, culminating in Claudius Ptolemy's Almagest (circa 150 CE), which cataloged 48 constellations—predominantly northern, including Ursa Major, Draco, and Cassiopeia—with positions for 1,022 stars derived from observations in Alexandria.^[49] This geocentric framework systematized the northern sky's geometry relative to the celestial equator, influencing subsequent European astronomy and serving as a reference for quadrant-based measurements.^[50] Independently, Chinese astronomy divided the northern celestial hemisphere into 28 lunar mansions (xiu), with the 4th-century BCE star catalog attributed to Shi Shen listing over 800 stars grouped into 122 asterisms, primarily along the ecliptic and circumpolar regions for calendrical and astrological purposes.^[51] Medieval Islamic scholars advanced these catalogs through precise observations; Abd al-Rahman al-Sufi's Book of Fixed Stars (964 CE) illustrated and described northern constellations based on Ptolemaic data augmented by his own sightings from Isfahan, notably identifying the Andromeda Galaxy as a "small cloud" distinct from stars.^[52] This work, incorporating Arabic translations and refinements, enhanced depictions of northern deep-sky objects like the Pleiades and Orion's belt.^[53] In the modern era, the International Astronomical Union (IAU) standardized the northern celestial hemisphere by delimiting boundaries for all 88 constellations in 1928, extending Ptolemaic patterns to cover the entire sky uniformly and resolving overlaps in northern regions like the Big Dipper.^[54] The 1997 release of the Hipparcos Catalogue by the European Space Agency provided high-precision astrometric data—positions accurate to 0.001 arcseconds—for 118,218 stars, with significant coverage of northern constellations to refine proper motions and distances.^[55] This satellite-based survey marked a pivotal advancement in mapping the northern sky's stellar framework.^[56]

Mythological Representations

In Greek mythology, the constellation Ursa Major represents Callisto, a nymph and devoted follower of Artemis who was seduced by Zeus in the guise of the goddess, leading to her pregnancy and subsequent transformation into a bear by the jealous Hera; to prevent her son Arcas from slaying her unknowingly, Zeus placed her in the sky as the Great Bear.^[57] Similarly, Cassiopeia, the vain queen of Aethiopia and wife of King Cepheus, boasted of her beauty surpassing that of the Nereids, incurring Poseidon's wrath; as punishment, she was bound to a throne in the heavens, eternally circling the celestial pole in a position that sometimes appears upside down.^[58] In Norse tradition, the constellation Auriga is interpreted as "asar bardagi," or the battlefield of the Aesir gods, evoking the cosmic struggles among the deities in their eternal conflicts.^[59] Among Native American cultures, such as the Iroquois, the Pleiades are seen as the Seven Dancers—seven boys who danced so fervently on a hill that they ascended into the sky, continuing their eternal dance as a reminder to future generations to consider the welfare of their descendants.^[60] Polynesian sailors, originating from southern latitudes, incorporated northern stars like Vega into their wayfinding lore through knowledge gained via ancient trade routes; known as the "year star" or whetu o te tau in northern Polynesian traditions, Vega marked the onset of the planting season and rainy period, symbolizing renewal and guiding voyages northward.^[61] Cross-culturally, the serpentine constellation Draco embodies a dragon figure across traditions, representing guardianship of the north celestial pole; in European lore, it is Ladon, the hundred-headed serpent protecting the Hesperides' golden apples, while in Chinese cosmology, it is known as the Heavenly Dragon (Tianlong), a celestial guardian coiling around the north pole.^[62]^[63]

References

[1]
Sky Tellers - Constellations - Lunar and Planetary Institute
Earth's equator, extended into space, intersects the sphere at the celestial equator, dividing it into northern and southern hemispheres. All stars and objects ...
[2]
Celestial Sphere
It is measured north and south of the celestial equator and ranges from 0° at the celestial equator to 90° at the celestial poles, being taken to be positive ...
[3]
Identify Constellations - AstroEdWiki
Aug 24, 2022 · Constellations seen from the Northern Hemisphere by Season · Aquila (Altair) · Corona Borealis · Cygnus (Deneb in the Northern Cross) · Draco ...
[4]
The North Celestial Pole - Solar Physics at MSU
The North Celestial Pole is the point in the sky about which all the stars seen from the Northern Hemisphere rotate. The North Star, also called Polaris, is ...
[5]
Celestial Sphere - UC Berkeley Astronomy w
Fortunately, for those of us in the northern hemisphere, there is a fairly bright star real close to the North Celestial Pole (Polaris or the North star).
[6]
Navigating The Summer Night Sky - Boise State University
Jun 12, 2024 · Here in the Northern Hemisphere, we have 5 notable circumpolar constellations: Ursa Major, Ursa Minor, Draco, Cepheus, and Cassiopeia.
[7]
What Are Constellations? | NASA Space Place
Chart showing some of the constellations that are visible from the Northern Hemisphere in different times. A chart showing some of the constellations that ...
[8]
Celestial Landmarks of the Northern Sky - NOIRLab
Jun 7, 2023 · Two celestial landmarks of the northern hemisphere: The constellation Ursa Major (the Great Bear), with its seven bright stars that make the Big Dipper.
[9]
Chapter 2: Reference Systems - NASA Science
Jan 16, 2025 · A useful construct for describing locations of objects in the sky is the celestial sphere, which is considered to have an infinite radius.
[10]
Latitude and the stars: Location is key - EarthSky
Jan 30, 2023 · If you're standing at the North Pole, you'll see the entire northern half of the celestial sphere visible every single night, except in the ...
[11]
[PDF] 2. Descriptive Astronomy (“Astronomy Without a Telescope”)
Right Ascension and Declination. ". CE. Page 27. What can be seen from a given ... Actual Coordinates of Polaris: Declination = 89o 15' 51”. RA = 2h 31m ...
[12]
Reference Frames
Dec 31, 2021 · The International Celestial Reference System (ICRS) defines coordinate axes that are closely aligned with those of the J2000 (aka EME2000) ...
[13]
Northern Constellations
Northern constellations are those found in the northern celestial hemisphere, located north of the celestial equator.
[14]
Equatorial Constellations
Aquarius; Aquila; Canis Minor; Cetus; Eridanus; Hydra; Leo; Monoceros; Ophiuchus; Orion; Pisces; Serpens; Sextans; Taurus; Virgo. Equatorial constellations ...
[15]
Constellation boundaries - Ian Ridpath
A clearly defined system of constellation boundaries to the IAU's second General Assembly, held in Cambridge, England, in 1925.
[16]
http://www.ianridpath.com/boundaries.html
[17]
Arcturus
### Summary of Arcturus Data
[18]
Polaris
### Summary of Basic Data for Polaris
[19]
Vega
### Summary of Vega Data
[20]
Capella
**Basic Data for Capella:**
[21]
Altair
### Summary of Altair Data
[22]
http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Capella
[23]
The Galaxy Next Door - NASA
May 15, 2012 · At approximately 2.5 million light-years away, the Andromeda galaxy, or M31, is our Milky Way's largest galactic neighbor.
[24]
Messier 45 (The Pleiades) - NASA Science
Aug 28, 2017 · Commonly called the Pleiades or Seven Sisters, M45 is known as an open star cluster. It contains over a thousand stars that are loosely bound by gravity.
[25]
Messier 42 (The Orion Nebula) - NASA Science
The nebula is only 1,500 light-years away, making it the closest large star-forming region to Earth and giving it a relatively bright apparent magnitude of 4.
[26]
Messier 13 (The Hercules Cluster) - NASA Science
Like shiny flakes sparkling in a snow globe, over 100,000 stars whirl within the globular cluster M13, one of the brightest star clusters visible from the ...
[27]
Messier 57 (The Ring Nebula) - NASA Science
Aug 28, 2017 · Messier 57, more commonly known as the Ring Nebula, is about 2,000 light-years away in the constellation Lyra. Discovered by the French ...
[28]
Celestial Sphere - JIM KALER
The intersection of the celestial meridian and the horizon define north (N) and south (S), while that between the equator and the horizon define east (E) and ...
[29]
Circumpolar Constellations: Visible All The Year Round - Star Walk
The latitude at which an object becomes circumpolar can be calculated as 90° minus its declination. For example, a star with a declination of +60° will always ...How Many Circumpolar... · Northern Circumpolar... · Ursa Minor<|separator|>
[30]
Night Sky - Introduction to Astronomy
Polaris is at 90o declination. The south celestial pole (no star there) is at -90o declination. If you think about this for a moment, you will realize ...
[31]
Constellation: Orion - NOIRLab
Rigel, Betelgeuse ...
[32]
Ohio SkyLites - December 2022
Dec 1, 2022 · The winter season officially starts this month! Therefore, it's time to highlight the most popular winter constellation: Orion (and Taurus). ...
[33]
The Summer Triangle - Astro Daily - New Mexico Tech
Jul 16, 2020 · The Summer Triangle is made up of the stars Altair, Deneb, and Vega, the brightest stars in the constellations Aquila, Cygnus, and Lyra respectively.
[34]
Here Comes the Sun: Seasons and Solstices
The Spin Axis of the Earth and importance of its 23.5 degree tilt. The Earth rotates along the plane of the equator, meaning that the Earth spins in a circle ...
[35]
The Height of the Sun | ASTRO 801 - Welcome to EMS Online Courses
... celestial equator would be 23.5 degrees because of the tilt of the Earth. ... Angle between the Celestial Equator and the Ecliptic on the Summer Solstice.
[36]
Time Scales - Introduction to Astronomy
The sidereal day is 23 hours and 56 minutes long. Solar day: This is the length of time it takes for the Earth to come around to the same position relative to ...
[37]
Clocks - Astronomy 505
Given that an apparent solar day is 24 solar hours in length, this means that a sidereal day is only 23h56m long in solar units and represents the rotational ...
[38]
Navigation and Related Instruments in 16th-Century England
Polaris was the preferred star for measuring latitude because it is less than one degree from the north celestial pole (the point in the heavens directly above ...
[39]
Star Positions
For example, in the northern hemisphere, the angle between the horizon and Polaris provides a close approximation of latitude. The angle at which stars rise and ...Missing: historical | Show results with:historical
[40]
Chapter 2: Reference Systems - NASA Science
Jan 16, 2025 · Throughout the history of navigation, determining one's latitude on the Earth's surface has been relatively easy. In the northern hemisphere for ...
[41]
Use the Big Dipper to find Polaris, the North Star - EarthSky
Mar 16, 2025 · To find Polaris, use the two outer stars in the Big Dipper's bowl, known as the Pointers, which point to Polaris. If you can see the Big Dipper ...
[42]
Kochab - JIM KALER
About the year 1100 BC, the pole made a reasonably close pass to Kochab, and there are old references to Kochab being called "Polaris." Precession also causes ...
[43]
Kochab and Pherkad: The Guardians of the Pole - EarthSky
Aug 31, 2022 · Kochab was known as the pole star and sometimes called Polaris between 1700 BCE and 300 CE. The closest the north celestial pole came to Kochab ...
[44]
BEA: Hesiod - Le Moyne
Arcturus marks seasonal tasks as well: at its sunset (acronycal) rising in February, the vines must be pruned (564 ff.); at its heliacal rising (September) ...Missing: Spica mnemonic
[45]
[PDF] Hesiod's calendar and the star Spica1 - arXiv
In Hesiod's calendar, circa 8th century BCE, the harvest times of cereals were indicated by the heliacal rising of Pleiades (harvest) and by that of Orion ( ...Missing: mnemonic | Show results with:mnemonic
[46]
Origins of the ancient constellations: I. The Mesopotamian traditions
SAO/NASA ADS Astronomy Abstract Service. Origins of the ancient constellations: I. The Mesopotamian traditions John H. Rogers In the sky-map ofancient ...
[47]
The Enigma of Ptolemy's Catalogue of Stars - NASA ADS
... 48 constellations and nearby unformed stars. It is ... northern constellations while Cancer to Scorpio and southern constellations show no such excess.
[48]
[PDF] The Night Sky Storytelling in the Stars
The “Almagest”, a treatise of all astronomical knowledge of the time, was written by the Greek astronomer Ptolemy in the 2nd century AD. It lists 48 ...
[49]
[PDF] 13 · Chinese and Korean Star Maps and Catalogs
The numbers of asterisms and stars noted in Han texts bear no relation to the figures that were later attributed to Zhanguo astronomers such as Shi Shen.Missing: BCE | Show results with:BCE
[50]
galaxy_discovery.html - UNLV Physics
Medieval Islamic astronomer al-Sufi (903--986) in his Book of the Fixed Stars (circa 964) is the first to put the Andromeda nebula (now known as the Andromeda ...
[51]
Introductory Astronomy Lectures (IAL) - UNLV Physics
Remarkably the Andromeda Galaxy was missed by Ptolemy (c. 90--c. 168 CE) as a cloudy star in his catalog of 1022 stars in 48 constellations. He labeled 5 stars ...
[52]
The Constellations - International Astronomical Union | IAU
Figure 1: The Dark Constellations of the Inca – right to left: (1) Machacuay, (2) Hanp'atu, (3) Yutu, (4) Yacana, (5) Uñallamacha, (6) Atoq, and (7) Michij ...
[53]
[PDF] The Hipparcos and Tycho Catalogues - ESA Cosmos
Inset: sky map of the mean observation epoch of stars in the Hipparcos Catalogue, relative to J1991.25, in ecliptic coordinates. Published by: ESA Publications ...Missing: constellations | Show results with:constellations
[54]
The HIPPARCOS Data and Resolving the Problems in the Northern ...
In this connection, the problems of northern area of the sky are discussed. ... 1997). The catalogue contains 4272 stars north of 800 declination. The mean ...
[55]
CALLISTO (Kallisto) - Arcadian Princess of Greek Mythology
In Greek mythology Callisto was a daughter of the Arcadian King Lycaon and a hunting companion of the goddess Artemis. There were several contradictory ...
[56]
ETHIOPIAN CETUS (Ketos Aithiopios) - Sea-Monster of Greek ...
In Greek mythology the Cetus Aethiopius was a sea-monster sent by Poseidon to ravage the land of Ethiopia as punishment for Queen Cassiopeia's hubristic ...<|control11|><|separator|>
[57]
Norse Constellations - Digitalis Education Solutions
One constellation which has a peculiar name is Auriga, which is called ”asar bardagi”. The battlefield or the fight of the asar. Beckman and Kålund interpret ...
[58]
The Seven Dancers (Origin of Pleiades) - Six Nations Polytechnic
The Seven Dancers continue their dance in the evening sky reminding the Ogweho:weh that they must think seven generations into the future about the welfare of ...Missing: American | Show results with:American
[59]
Western Slope Skies - The Significance of the Summer Triangle
Jun 24, 2022 · The northern Polynesian people called Vega the “year star.” Seeing it marked the beginning of the new planting season and ushered in the ...
[60]
Star Tales – Draco - Ian Ridpath
Draco is a Greek constellation, a celestial dragon coiled around the north pole, and the 8th largest by area. It is linked to the dragon slain by Heracles.
[61]
Draco | Encyclopedia MDPI
Mar 8, 2024 · In Chinese mythology, Draco is often associated with the myth of the Azure Dragon, one of the four celestial guardians in Chinese cosmology. ...