Celestial Coordinates

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Erstellt für das OAE

Unterschrift: Here we see how celestial coordinates map positions on the celestial sphere. The celestial sphere is an imaginary, hollow sphere that surrounds the Earth. Celestial objects appear to be attached to the inside of the celestial sphere, and the planets, Sun, and Moon appear to move slowly across it. The celestial sphere has a spherical coordinate system similar to the latitude and longitude we see on the Earth. The celestial equator is the projection of the Earth's equator onto the celestial sphere while the north and south celestial poles are the projections of the Earth's north and south poles onto the celestial sphere. Declination is similar to latitude on the Earth in that it marks the angle above and below the celestial equator. Declination is zero on the celestial equator, is positive to the north of the celestial equator and negative to the south of it. It is commonly measured in degrees and sometimes in radians. Right Ascension is similar to longitude as it marks the angle around the celestial equator. As with longitude the zero point of right ascension (shown here as a dashed line) is a matter of choice. Traditionally the zero point of right ascension was the position of the Sun at the northern hemisphere vernal equinox (spring equinox) in March. It is positive and increases to the east, unlike longitude on Earth which is defined as east or west of the prime meridian. It is most commonly measured in hours, minutes and seconds or occasionally in degrees or radians. The ecliptic marks the Sun's path across the celestial sphere when viewed from the Earth. The Earth rotates within the celestial sphere. This leads to objects like stars or galaxies, which appear static on the celestial sphere, rising and setting when viewed from the Earth but remaining in the same position on the celestial sphere. The Earth's axis precesses within the celestial sphere. This slowly moves the celestial equator and the celestial poles meaning that the traditional celestial coordinate system changes slowly over time meaning that stars and galaxies that do not move will have positions that change. Astronomers have used coordinate systems defined by the position of the celestial poles and equator at a fixed point in time. Now celestial positions are most commonly measured on a fixed coordinate system defined by the position of the celestial poles and equator on the 1st of January 2000.
Bild: Maria Cristina Fortuna/IAU OAE

Kategorien: Astronomie mit bloßem Auge , Beobachtende Astronomie

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Taurus Constellation Map

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Unterschrift: The constellation Taurus along with its bright stars and surrounding constellations. Taurus is surrounded by (going clockwise from the top) Perseus, Aries, Cetus, Eridanus, Orion, Gemini and Auriga. Taurus’s brightest star Aldebaran appears in the middle of the constellation. Taurus lies on the ecliptic (shown here as a blue line), this is the path the Sun appears to take across the sky over the course of a year. The Sun is in Taurus from mid May to late June. The other planets of the Solar System can often be found in Taurus. Taurus lies mostly north of the celestial equator with a small part in the celestial southern hemisphere. The whole constellation is visible at some point in the year to whole planet except for the Antarctic and a small region around the North Pole. Taurus is most visible in the evenings in the northern hemisphere winter and southern hemisphere summer. In the eastern part of Taurus we can find the supernova remnant M1 (commonly known as the Crab Nebula), marked here with a green square. In Taurus’s north-east find one of the sky’s most famous open stars clusters M45 (the Pleiades), marked here with a yellow circle. Many of the stars near Aldebaran (but not) Aldebaran are members of another star cluster, the Hyades. However this cluster is close to the solar system so is too dispersed on the sky to have a Messier object designation like the Pleiades has. The y-axis of this diagram is in degrees of declination with north as up and the x-axis is in hours of right ascension with east to the left. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. Neither the constellation boundaries, nor the line marking the ecliptic, nor the lines joining the stars appear on the sky.
Bild: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope
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Glossar-Begriffe: Scheinbare Helligkeit , Widder , Himmelskoordinaten , Sternbild , Deklination , Ekliptik , Zwillinge , Rektaszension (RA) , Stier , Tierkreis , Offener Sternhaufen , Orion , Plejaden , Supernova-Überrest
Kategorien: Astronomie mit bloßem Auge

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Waage-Sternbildkarte

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Unterschrift: Das Sternbild Waage mit seinen hellen Sternen und den umliegenden Sternbildern. Die Waage ist im Uhrzeigersinn von oben gehend umgeben von dem Kopf der Schlange, Jungfrau, Wasserschlange, Zentaur, Wolf, Skorpion und Schlangenträger. Die Waage liegt auf der Ekliptik (hier als blaue Linie dargestellt), das ist der Weg, den die Sonne im Laufe eines Jahres über den Himmel zu nehmen scheint. Die Sonne befindet sich von Ende Oktober bis Ende November in der Waage. Die anderen Planeten des Sonnensystems sind oft in der Waage zu finden. Die Waage liegt knapp südlich des Himmelsäquators und ist daher in allen Regionen mit Ausnahme der arktischsten im Laufe des Jahres irgendwann einmal sichtbar. Am besten zu sehen ist die Waage abends auf der Nordhalbkugel im späten Frühling/Frühsommer und auf der Südhalbkugel im Spätherbst/Frühwinter. Die y-Achse dieses Diagramms ist in Deklinationsgraden mit Norden nach oben und die x-Achse in Stunden der Rektaszension mit Osten nach links. Die Größe der hier markierten Sterne bezieht sich auf die scheinbare Helligkeit des Sterns. Je größer die Punkte, desto heller scheinen die Sterne die sie darstellen. Die griechischen Buchstaben kennzeichnen die hellsten Sterne des Sternbildes. Diese sind nach Helligkeit geordnet, wobei der hellste Stern mit Alpha, der zweithellste mit Beta usw. bezeichnet wird, obwohl diese Reihenfolge nicht immer genau eingehalten wird. Die gepunkteten Begrenzungslinien markieren die IAU-Grenzen der Sternbilder und die durchgezogenen grünen Linien markieren eine der üblichen Formen, die zur Darstellung der Sternbilder verwendet werden. Weder die Sternbildgrenzen, noch die Linie, die die Ekliptik markiert, noch die Linien, die die Sterne verbinden, sind am Himmel sichtbar.
Bild: Angepasst vom IAU Office of Astronomy for Education nach dem Original von IAU/Sky & Telescope
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Glossar-Begriffe: Scheinbare Helligkeit , Himmelskoordinaten , Sternbild , Deklination , Ekliptik , Waage , Rektaszension (RA) , Skorpion , Tierkreis , Jungfrau
Kategorien: Astronomie mit bloßem Auge

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Delphinus Constellation Map

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Unterschrift: The constellation Delphinus with its brighter stars and surrounding constellations. Delphinus is surrounded by (going clockwise from the top): Vulpecula, Sagitta, Aquila, Aquarius, Equuleus and Pegasus. Delphinus is a relatively small constellation with few bright stars. Delphinus lies just north of the celestial equator and thus the whole constellation is visible at some point in the year to all but the most antarctic regions. The constellation is best viewed in the evenings in the early northern hemisphere autumn and early southern hemisphere spring. The globular cluster NGC 6934 lies in Dephinus. It is marked here with a yellow circle with a plus sign superimposed on it. The y-axis of this diagram is in degrees of declination with north as up and the x-axis is in hours of right ascension with east to the left. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. Neither the constellation boundaries, nor the lines joining the stars appear on the sky.
Bild: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
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Glossar-Begriffe: Scheinbare Helligkeit , Himmelskoordinaten , Himmelsäquator , Sternbild , Deklination , Kugelsternhaufen , Rektaszension (RA) , Wassermann
Kategorien: Astronomie mit bloßem Auge

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Aries Constellation Map

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Unterschrift: The constellation Aries along with its bright stars and surrounding constellations. Aries is surrounded by (going clockwise from the top) Triangulum, Pisces, Cetus, Taurus and Perseus. Aries lies on the ecliptic (shown here as a blue line), this is the path the Sun appears to take across the sky over the course of a year. The Sun is in Aries from mid April to mid May. The other planets of the Solar System can often be found in Aries. Aries lies just north of the celestial equator and is thus visible at some time in the year from all of planet Earth except for the most antarctic regions of the world. Aries is most visible in the evenings in the northern hemisphere winter and southern hemisphere summer. The y-axis of this diagram is in degrees of declination with north as up and the x-axis is in hours of right ascension with east to the left. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. Neither the constellation boundaries, nor the line marking the ecliptic, nor the lines joining the stars appear on the sky.
Bild: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope
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Glossar-Begriffe: Scheinbare Helligkeit , Widder , Himmelskoordinaten , Sternbild , Deklination , Ekliptik , Fische , Rektaszension (RA) , Stier , Tierkreis
Kategorien: Astronomie mit bloßem Auge

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