Caption: Mention honorable au concours d'astrophotographie 2022 de l'UAI OAE, catégorie Images fixes de motifs célestes. Prise en mars 2016 dans le parc national de Bromo-Tengger-Semeru, sur l'île de Java, en Indonésie, cette image montre l'arc de la Voie lactée et de nombreuses constellations importantes, y compris la plupart des étoiles les plus brillantes du ciel nocturne. Dans le coin inférieur gauche, nous voyons alpha et bêta du Centaure, le premier plus bas et l'autre plus haut, tous deux situés dans la grande constellation du Centaure. Ils pointent vers la Croix du Sud, dont le grand axe pointe vers le pôle sud, qui se trouve à peu près à l'horizon car l'île de Java est presque à l'équateur. La Croix du Sud est presque entièrement obscurcie par les nuages, et seules les quatre étoiles brillantes sont visibles sur la photo. L'astérisme de la fausse croix (composé des étoiles d'Argo, le navire) est clairement visible un peu plus loin dans la Voie lactée, ce qui peut prêter à confusion. La tache rosée entre la vraie et la fausse croix est la nébuleuse de la Carène, située à environ 8500 années-lumière de la Terre, dans la constellation de la Carène, et invisible à l'œil nu. Dans la constellation de la Carène se trouve également Canopus, la deuxième étoile la plus brillante du ciel nocturne, visible juste en dessous de la galaxie et au-dessus de la route au sol. Sirius, l'étoile la plus brillante du ciel nocturne, est encore plus brillante. Sirius se trouve dans la constellation Canis Major, le Grand Chien, l'un des chiens qui suivent Orion, le Chasseur, représenté dans la moitié droite de cette image, juste au-dessus des nuages à l'horizon. La ceinture d'Orion, composée de trois étoiles brillantes, pointe vers Sirius en haut à gauche et vers Aldébaran en bas à droite, juste au-dessus de l'horizon. Orion contient certaines des étoiles les plus brillantes du ciel, ce qui en fait la constellation la plus colorée, car elle abrite Rigel, l'étoile bleuâtre brillante située sous la galaxie vers la droite, et Bételgeuse, l'étoile rougeâtre brillante située plus haut et à droite de Rigel. Entre elles se trouvent les trois étoiles qui forment la ceinture d'Orion, un astérisme célèbre. Juste à côté de la ceinture se trouve la Grande Nébuleuse d'Orion, une région de formation d'étoiles dont le centre brillant est visible à l'œil nu et également sur cette image. Au-dessus de Bételgeuse, mais de l'autre côté de la galaxie, nous voyons l'étoile brillante Procyon, dont le nom signifie littéralement "Avant le chien". D'un point de vue mythologique, elle est souvent considérée comme un petit astérisme à une étoile accompagnant Orion, et transformé en la constellation moderne de Canis Minor. Dans le coin supérieur droit, l'amas d'étoiles de la Ruche, dans la constellation du Cancer, est facilement reconnaissable. En dessous, on trouve la constellation des Gémeaux avec les étoiles Pollux et Castor, qui ne sont pas très visibles sur cette image. En revanche, la brillante étoile blanche Capella de la constellation du Cocher, le Chariot, brille à travers les nuages au milieu à droite de l'image. Une certaine pollution lumineuse est visible le long de la route.
Credit: Giorgia Hofer/IAU OAE

Caption: The zodiac constellation Cancer and its surrounding constellations. Starting from the top of the diagram and going clockwise, these are Lynx, Gemini, Canis Minor, Hydra, Leo and Leo Minor. The ecliptic (shown here as a blue line) passes almost exactly through the middle of the constellation, this is the path the Sun appears to take across the sky over the course of a year. The Sun is in Cancer from late July to mid August. The other planets of the Solar System can often be found in Cancer. Cancer 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. Cancer is most visible in the evenings in the northern hemisphere spring and southern hemisphere autumn. Two star clusters are visible in Cancer: M44, an open cluster often called the Beehive Cluster, and M46, a denser open cluster with about four times more stars than M44. These clusters are indicated by yellow circles with a dotted border on the map. 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 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 zodiac constellation Leo and its surrounding constellations. Starting from the top of the diagram and going clockwise, these are Leo Minor, Cancer, Sextans, Hydra, Crater, Virgo and Ursa Major. The brightest star in Leo, Regulus, lies almost exactly on the ecliptic (shown here as a blue line): the path the Sun appears to take across the sky over the course of a year. The Sun spends the period from mid August to mid September in Leo. The other planets in the Solar System can often be found in Leo. Leo spans the celestial equator and is thus part of it is visible at some time in the year from all of planet Earth with some of the constellation obscured for the most arctic and antarctic regions of the world. Leo is most visible in the evenings in the northern hemisphere spring and southern hemisphere autumn. Several objects can be seen in Leo, including M65 and M66 – two galaxies in the Leo Triplet, a trio of galaxies including NGC 3628, not listed here. In addition, M96, a spiral galaxy, can be seen as a fuzzy object using a small telescope, and Messier 105, an elliptical galaxy. Each of these objects are labelled on the map as red ellipses. 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 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 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