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Glossary term: Aries

Description: Aries is the smallest constellation in the Zodiac. The stars that make up this constellation are in the part of the sky that intersects with the ecliptic (the plane defined by the orbit of the Earth around the Sun). Hence, from Earth, we can regularly find the planets, and also the Sun, in the constellation Aries. In the case of the Sun this occurs from mid-April to mid-May (at that time, of course, we cannot see the constellation's stars). Aries is one of the 88 modern constellations defined by the International Astronomical Union, but goes back much further – it was already one of the 48 constellations named by the 2nd century astronomer Claudius Ptolemy.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

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A group of observatories in-front of a dark sky. An arc of light curves from the bottom left. Several stars are visible.

Chilean observatories at home office, by Robert Barsa, Slovakia

Caption: Third place in the 2021 IAU OAE Astrophotography Contest, category Wide star fields. This rich panoramic image shows a range of constellations, deep sky objects and planets. The brightest point of light with a pale reddish hue (left of center) is the planet Mars. In the bottom far left of the image, located just above the sloped roof of the building are two points of light appearing very close to each other, these are the planets Jupiter (brighter) and Saturn. To the far right of the image the two fuzzy cloud-like objects are the Large and Small Magellanic Clouds. These are satellite dwarf galaxies of the Milky Way located at a distance of approximately 160,000 and 200,000 light years, respectively. The Andromeda Galaxy, which is located at an approximate distance of 2.5 million light years, appears in this image as a small, angled smudge between Mars and the brightest glow on the horizon (closer to the horizon). The bright glow is not from the Sun or the Moon, but the city lights of San Pedro de Atacama. Prominent constellations include: Orion – identified by the three stars forming Orion’s Belt; Taurus – a small triangle shaped collection of stars to the left of Orion and identified by the pale orange star (Aldebaran) at the vertex of the triangle; Canis Major – to the bottom right of Orion, identified by the bright star Sirius (the brightest star in the night sky) and three stars in the shape of a triangle just above the observatory dome in the foreground; Pegasus – identified by the trapezium shape diagonally below Mars. Other constellations include Andromeda, Perseus and Aries. Diverse cultures around the world have their own names and rich stories associated with these constellations and many others. To the top right of Orion’s Belt is an angled line of stars (Orion’s Sword) within which is a pinkish smudge (looks like a fuzzy star when observed with the unaided eye) that is the Orion Nebula – a stellar nursery located 1500 light years from Earth – where stars are formed. To the left of Taurus is a compact fuzzy smudge, and that is the Pleiades star cluster. The variation in the colour of stars is the result of temperature of the stars, for example, the red orange star to the bottom left of Orion’s Belt is the red giant star Betelgeuse. Cooler stars appear redder, compared to the higher temperature white and bluish stars. The colours in the image are enhanced because of the higher sensitivity of the digital camera compared to the human eye.
Credit: Robert Barsa/IAU OAE

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons