Gemini Constellation Map

image

Légende : The zodiac constellation Gemini and its surrounding constellations. Starting from the top of the diagram and going clockwise, these are Auriga, Taurus, Lynx, Orion, Monoceros, Canis Minor and Cancer. The brightest stars in Gemini, Castor and Pollux appear in the upper lefthand corner (north-east) of the diagram. In Greek mythology, the stars in this constellation are thought to resemble twins with their arms wrapped around each other, with Castor and Pollux indicating their heads. Gemini 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 Gemini from late June to late July. The other planets of the Solar System can often be found in Gemini. Gemini lies north of the celestial equator and is visible in all but the antarctic regions of the world. Gemini is most visible in the evenings in the northern hemisphere winter and southern hemisphere summer. Just to the right of the foot of the Castor twin is an open cluster of stars (labelled as a yellow circle with a dotted line border), Messier 35, also known as the Shoe-Buckle Cluster. This cluster is spread out over an area roughly the size of the full moon. In addition to this cluster of stars, there is a planetary nebula (labelled as a green circle with four radial spikes) – NGC 2392 – near the celestial equator and just to the left of the Pollux twin. Two variable stars (Mekbuda and Propus; labelled as two concentric circles) can be found in the “legs” of each twin, but are so faint that an observer would need dark skies to see them. 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 labelled 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.
Crédit : Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope
Lien du crédit

Termes du glossaire: Magnitude apparente , Coordonnées célestes , Constellation , Déclinaison , Ecliptique , Gémeaux , Ascension droite (AD) , Taureau , Zodiaque
Catégories : Astronomie à l'œil nu

Licence : Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Icônes

Fichier ( image 111.96 kB)
Fichier PDF (PDF file 187.83 kB)

Centaurus Constellation Map

image

Légende : The constellation Centaurus with its bright stars and surrounding constellations. Centaurus is surrounded by (going clockwise from the top): Hydra, Antlia, Vela, Carina, Musca, Crux, Circinus, Lupus and Libra. Centaurus is a large constellation most notable for its brightest star Alpha Centauri. Alpha Centauri is a triple star system and is the nearest star system to the Solar System. When viewed with the naked eye, the two brightest components of Alpha Centauri appear as one star. The combined light from these two stars makes Alpha Centauri appear as the third brightest star in the night sky. The third component of the Alpha Centauri system Proxima Centauri, the nearest star to the Sun, is too faint to be viewed with the naked eye. Centaurus is a southern constellation and thus the whole constellation is visible from the southern hemisphere at some point in the year. The whole constellation is also visible from equatorial regions of the northern hemisphere with parts of the constellation visible from temperate northern regions. The constellation is best viewed in the evening in the late northern hemisphere spring and late southern hemisphere autumn. The globular cluster Omega Centauri, also known as NGC 5319, lies in Centaurus. Bright enough to be seen with the naked eye, this cluster was initially given a designation as a star in the constellation before its true nature was realised. It is marked here with a yellow circle with a plus sign superimposed on it. As is the globular cluster NGC 5286. The open cluster NGC 3766 is marked here with a yellow circle. NGC 5128, also known as Centaurus A, is the closest active galaxy to Earth. The supermassive black hole at the heart of this galaxy has launched two huge jets of matter which emit in many different wavelengths including x-ray and radio emission. NGC 5128 is marked with a red ellipse here, as is the edge-on spiral galaxy NGC 4945. 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. The blue line in the top left is the ecliptic. Neither the constellation boundaries, nor the line marking the ecliptic, nor the lines joining the stars appear on the sky.
Crédit : Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
Lien du crédit

Termes du glossaire: Magnitude apparente , Coordonnées célestes , Constellation , Déclinaison , Amas globulaire , Ascension droite (AD) , Amas ouvert , Alpha du Centaure
Catégories : Astronomie à l'œil nu

Licence : Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Icônes

Fichier ( image 152.88 kB)
Fichier PDF (PDF file 255.96 kB)

Corona Australis Constellation Map

image

Légende : The constellation Corona Australis with its brighter stars and surrounding constellations. Corona Australis is surrounded by (going clockwise from the top): Sagittarius, Scorpius, Ara and Telescopium. This constellation has relatively few bright stars. Corona Australis is a southern constellation and thus the whole constellation is visible in the southern hemisphere at some point in the year. The constellation can also be viewed from equatorial and some temperate regions of the northern hemisphere. The constellation is best viewed in the evening in the northern hemisphere summer and southern hemisphere winter. The globular cluster NGC 6541 lies in Corona Australis and 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. The blue line at the top right of the diagram marks the ecliptic.
Crédit : Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
Lien du crédit

Termes du glossaire: Magnitude apparente , Coordonnées célestes , Constellation , Déclinaison , Ecliptique , Amas globulaire , Ascension droite (AD) , Scorpius , Sagittaire
Catégories : Astronomie à l'œil nu

Licence : Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Icônes

Fichier ( image 88.22 kB)
Fichier PDF (PDF file 158.70 kB)

Leo Minor Constellation Map

image

Légende : The constellation Leo Minor with its brighter stars and surrounding constellations. Leo Minor is surrounded by (going clockwise from the top): Ursa Major, Lynx, Cancer and Leo. Leo Minor is a small constellation with relatively few bright stars. It is a separate constellation from and should not be confused with its larger neighbour Leo. Leo Minor is a northern constellation and thus the whole constellation is visible at some point in the year throughout the northern hemisphere. The whole constellation is also visible from equatorial and temperate regions of the southern hemisphere. Leo Minor is circumpolar in arctic regions. This constellation is best viewed in the northern hemisphere spring and southern hemisphere autumn. 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. The blue line in the bottom right marks the ecliptic.
Crédit : Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
Lien du crédit

Termes du glossaire: Magnitude apparente , Coordonnées célestes , Étoiles circumpolaires , Constellation , Déclinaison , Ecliptique , Leo , Ascension droite (AD)
Catégories : Astronomie à l'œil nu

Licence : Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Icônes

Fichier ( image 88.37 kB)
Fichier PDF (PDF file 154.05 kB)

Celestial Coordinates

image
Créé pour l'OAE

Légende : 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.
Crédit : Maria Cristina Fortuna/IAU OAE

Catégories : Astronomie à l'œil nu , Astronomie observationnelle

Licence : Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Icônes

Fichier ( image 517.83 kB)
Fichier PDF (PDF file 203.59 kB)

Also available in black and white
Fichier ( image 501.79 kB)
Fichier PDF ( 202.13 kB)