Caption: This Hubble Space Telescope image presents a view of the interiors of the densely packed globular cluster Terzan 9 which consists of millions of stars located close to the heart of our Milky Way galaxy. This globular cluster sits within the central galatic bulge amidst interstellar dust, which obscures light from these star clusters. This image is a combination of light seen in the visible and infrared parts of the electromagnetic spectrum. Multi-wavelength imaging of the color and brightness of stars helps determine their age and in turn age of the parent star cluster.
Credit: ESA/Hubble & NASA, R. Cohen credit link

Caption: The constellation Scorpius (often commonly called Scorpio) along with its bright stars and surrounding constellations. Scorpius is surrounded by (going clockwise from the top) Ophiuchus, Serpens Caput, Libra, Lupus, Norma, Ara, Corona Australis and Sagittarius. Scorpius’s brightest star Antares appears in the heart of the constellation with the famous tail of Scoprius in the south-east (lower left). Scorpius 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 only spends a short amount of time in late November in Scorpius. The other planets of the Solar System can often be found in Scorpius. Scorpius lies south of the celestial equator. The whole constellation is not visible from the most arctic regions of the world with parts of Scorpius obscured for observers in northern parts of Asia, Europe and North America. Scorpius is most visible in the evenings in the northern hemisphere summer and southern hemisphere winter. The yellow circles mark the positions of the open clusters M6, M7 & NGC 6231 while the yellow circles with plus signs superimposed on them mark the globular clusters M4 and M80. 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 circle around Antares indicates that it is a variable star. 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 marks the ecliptic, the path the Sun appears to travel across the sky over the course of one year.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope

Caption: The constellation Sagittarius along with its bright stars and surrounding constellations. Sagittarius is surrounded by (going clockwise from the top) Aquila, Scutum, Serpens Cauda, Ophiuchus, Scorpius, Corona Australis, Telescopium, Microscopium and Capricornus. The brighter stars in Sagittarius form a distinctive teapot shape. Sagittarius 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 Sagittarius from mid December to mid January. The other planets of the Solar System can often be found in Sagittarius. Sagittarius lies south of the celestial equator. The famous teapot asterism is visible for all but the most arctic regions of the world but the most southerly parts of the constellation are not visible in northern parts of Asia, Europe and North America. Sagittarius is most visible in the evenings in the northern hemisphere summer and southern hemisphere winter. The supermassive black hole Sagittarius A* which lies at the center of our Milky Way Galaxy is sits on the western (here right-hand) edge of Sagittarius. Due to it covering an area at the center of our Galaxy, Sagittarius is home to many star clusters including open clusters (marked here with yellow circles) and globular clusters (marked here with yellow circles with + signs superimposed on them). Three nebulae are also marked here with green squares. 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.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope

Caption: The constellation Capricornus (commonly called Capricorn) including its bright stars and surrounding constellations. Capricornus is surrounded by (going clockwise from the top) Aquarius, Aquila, Sagittarius, Microscopium and Piscis Austrinus. Capricornus 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 Capricornus from mid January to mid February. The other planets of the Solar System can often be found in Capricornus. Capricornus lies just south of the celestial equator and is visible to all observers south of the Arctic Circle. Capricornus is most visible in the evenings in the northern hemisphere autumn and southern hemisphere spring. In the south east (lower left on this diagram) of the constellation one can find the globular cluster M30 (shown here as 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.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope

Caption: The constellation Aquarius along with its bright stars and surrounding constellations. Aquarius is surrounded by (going clockwise from the top) Pegasus, Equuleus, Aquila, Capricornus, Piscis Austrinus, Sculptor, Cetus and Pisces. Aquarius 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 Aquarius from mid February to mid March. The other planets of the Solar System can often be found in Aquarius. Aquarius spans the celestial equator and is thus visible at some time in the year from all of planet Earth. In the most arctic or antarctic regions of the world, some parts of the constellation may not be visible. Aquarius is most visible in the evenings in the northern hemisphere autumn and southern hemisphere spring. The yellow circles with plus symbols superimposed on them mark the globular clusters M2 and M72. The green circles superimposed on plus symbols mark the planetary nebulae NGC 7293 (the Helix Nebula) and NGC 7002 (the Saturn Nebula). M73 (marked with an x symbol) is a coincident grouping of stars previously erroneously classified as an open cluster. 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.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope

Caption: The constellation Ophiuchus along with its bright stars and its surrounding constellations. Ophiuchus is surrounded by (going clockwise from the top): Hercules, Serpens Caput, Scorpius, Sagittarius and Serpens Cauda. Ophiuchus is not part of the traditional twelve zodiac constellations but it 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 Ophiuchus from late November to mid December. The other planets of the Solar System can often be found in Ophiuchus. Ophiuchus spans the celestial equator and thus part of the constellation is visible across the whole of the earth at some point in the year. However during the time it is most visible in the evenings (the southern hemisphere winter and northern hemisphere summer) much of the arctic is in perpetual daylight making the stars in the constellation impossible to see. The whole constellation is visible from equatorial and temperate regions of both hemispheres. As Ophiuchus lies close to the galactic center it contains many globular clusters such as M9, M10, M12, M14, M19, M62, and M107. These are marked as yellow circles with plus symbols superimposed. 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.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope

Caption: The constellation Ara along with its bright stars and surrounding constellations. Ara is surrounded by (going clockwise from the top): Scorpius, Norma, Triangulum Australe, Apus, Pavo, Telescopium and Corona Australis. Ara is a southern constellation that is visible from the entire southern hemisphere at some point in the year and is visible from equatorial with parts of the constellation visible from some temperate parts of the northern hemisphere. It is best viewed in the evening in the northern hemisphere summer and southern hemisphere winter. The globular clusters NGC 6352 and NGC 6397 lie in Ara. These are marked here with yellow circles with plus symbols superimposed on them. The open cluster NGC 6193 also lies in Ara, this is marked here with a yellow circle that is partially obscured by the dot marking the brightest member of the cluster which is visible to the naked eye under good conditions. 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.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope

Caption: 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. Neither the constellation boundaries, nor the lines joining the stars appear on the sky. The blue line in the top left is the ecliptic.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope

Caption: 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.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope

Caption: The constellation Canes Venatici with its brighter stars and surrounding constellations. Canes Venatici is surrounded by (going clockwise from the top): Ursa Major, Coma Berenices and Boötes. Canes Venatici is a northern constellation and thus the whole constellation is visible at some point in the year from the whole of the northern hemisphere. The whole of the constellation is also visible from equatorial regions of the southern hemisphere with parts of it visible from temperate southern regions. The constellation is best viewed in the northern hemisphere late spring and southern hemisphere late autumn. The famous spiral galaxy commonly known as the Whirlpool Galaxy (M51) lies in Canes Venatici and is marked here with a red ellipse. Other notable spiral galaxies in the cluster include M63, M94, M106 and NGC 4631. All are marked here with red ellipses. The globular cluster M3 is marked here with a yellow circle with a plus symbol 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.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope

Caption: 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.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope

Caption: The constellation Hercules with its bright stars and surrounding constellations. Hercules is surrounded by (going clockwise from the top): Draco, Boötes, Corona Borealis, Ophiuchus, Aquila, Sagitta, Vulpecula and Lyra. Hercules is a large, northern constellation that covers a big range in declination. The whole constellation is visible at some point in the year in the whole northern hemisphere and in equatorial regions of the southern hemisphere. Parts of the constellation can be viewed from temperate and almost all antarctic regions of the southern hemisphere. Hercules is best viewed in the northern hemisphere summer and southern hemisphere winter. The globular clusters M13 and M92 lie in Hercules and are marked here with yellow circles with plus signs superimposed on 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 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.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope

Caption: The constellation Horologium with its bright stars and surrounding constellations. Horologium is surrounded by (going clockwise from the top): Eridanus, Hydrus, Reticulum, Dorado and Caelum. Horologium is a southern constellation and thus is visible in the whole southern hemisphere at some point in the year. The whole constellation is also visible from equatorial parts of the northern hemisphere with parts of it visible to some northern temperate regions. Horologium is circumpolar in antarctic and some temperate regions of the southern hemisphere. This constellation is best viewed in the evenings in the northern hemisphere winter and southern hemisphere summer. The globular cluster NGC 1261 lies in Horologium, 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.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope

Caption: The constellation Hydra with its bright stars and surrounding constellations. Hydra is surrounded by (going clockwise from the top): Leo, Cancer, Canis Minor, Monoceros, Puppis, Pyxis, Antlia, Centaurus, Lupus, Libra, Virgo, Corvus, Crater and Sextans. Hydra is a large constellation that covers over a quarter of the celestial sphere in right ascension. It also spans the celestial equator and thus part of the constellation is visible from everywhere on the Earth at some point in the year. All parts of the constellation are visible at some point for all but the most antarctic parts of the southern hemisphere and to equatorial and most temperate regions of the northern hemisphere. However the wide span of the constellation means that all of it may not be visible at the same time in many of these regions. Hydra is best viewed in the northern hemisphere spring and southern hemisphere autumn. The famous spiral galaxy M83, also known as the Pinwheel Galaxy, lies in Hydra. It is marked here with a red ellipse. The planetary nebula NGC 3242 can also be found in Hydra. It is marked here with a green circle with a plus sign superimposed on it. The open cluster M48 is marked here with a yellow circle while the globular cluster M68 is marked 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 on the diagram marks the ecliptic.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope