The Aries Constellation

The Aries Constellation.

Aries Constellation is located in the northern celestial hemisphere between Pisces to the west and Taurus to the east. The name Aries is Latin for ram, representing a ram’s horns. It is one of the 48 constellations described by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations. It is a mid-sized constellation, ranking 39th overall size, with an area of 441 square degrees or 1.1% of the celestial sphere. Although Aries came to represent specifically the ram whose fleece became the Golden Fleece of Ancient Greek mythology, it has represented a ram since late Babylonian times. The best viewing month is in December at 9.00pm at right ascension 2h 41m, and declination 22degrees 34’.

Aries has three prominent stars forming an asterism, designated Alpha, Beta, and Gamma Arietis by Johann Bayer. There is also one other star above the fourth magnitude, 41 Arietis. α Arietis, called Hamal, is the brightest star in Aries. Its traditional name is derived from the Arabic word for “head of the ram” (ras al-hamal). With a spectral class of K2 and a luminosity class of III, it is an orange giant with an apparent visual magnitude of 2.00, which lies 66 light-years from Earth. β Arietis, also known as Sheratan, is a blue-white star with an apparent visual magnitude of 2.64. Its traditional name is derived from “sharatayn,” the Arabic word for “the two signs,” referring to both Beta and Gamma Arietis in their position as heralds of the vernal equinox. The two stars were known to the Bedouin as “qarna al-hamal,” “horns of the ram”. It is 59 light-years from Earth. γ Arietis, with a common name of Mesarthim, is a binary star with two white-hued components, located in a rich field of magnitude 8–12 stars. The primary is of magnitude 4.59 and the secondary is of magnitude 4.68. The system is 164 light-years from Earth. The two components are separated by 7.8 arcseconds, and the system as a whole has an apparent magnitude of 3.9. The constellation is home to several double stars, including Epsilon, Lambda, and Pi Arietis. ε Arietis is a binary star with two white components. Aries has its share of variable stars, including R and U Arietis, Mira-type variable stars, and T Arietis, a semi-regular variable star.

The few deep-sky objects within the constellation are quite faint and include several pairs of interacting galaxies; with spiral, elliptical, and interacting galaxies. NGC 772 is a class SA(s)b spiral galaxy with an integrated magnitude of 10.3, located southeast of β Arietis and 15 arcminutes west of 15 Arietis. It has a small companion galaxy, NGC 770, that is about 113,000 light-years away from the larger galaxy. The two galaxies together are also classified as Arp 78. NGC 772 has a diameter of 240,000 light-years and the system is 114 million light-years from Earth. Another spiral galaxy is NGC 673, a face-on class SAB(s)c galaxy. It is a weakly barred spiral galaxy with loosely wound arms. It is 171,000 light-years in diameter, and 235 million light-years from Earth. NGC 678 and NGC 680 are a pair of galaxies that are only about 200,000 light-years apart. NGC 877 is the brightest member of an 8-galaxy group that also includes NGC 870, NGC 871, and NGC 876, with a magnitude of 12.53. It is 2.4 by 1.8 arcminutes and is 178 million light-years away, with a diameter of 124,000 light-years. Its companion NGC 876 is about 103,000 light-years from the core of NGC 877. They are interacting gravitationally, as they are connected by a faint stream of gas and dust.

Several meteor showers appear to radiate from Aries, including the Daytime Arietids and the Epsilon Arietids. The Daytime Arietid meteor shower is one of the strongest meteor showers that occurs during the day, lasting from 22 May to 2 July. It is an annual shower associated with the Marsden group of comets that peaks on 7 June with a maximum zenithal hourly rate of 54 meteors. Its parent body may be the asteroid Icarus. Other meteor showers radiate from Aries during the day; these include the Daytime Epsilon Arietids and the Northern and Southern Daytime May Arietids.

Aries contains several stars with extrasolar planets. HIP 14810, a G5 type star, is orbited by three giant planets (those more than ten times the mass of Earth). HD 12661, like HIP 14810, is a G-type main sequence star, slightly larger than the Sun, with two orbiting planets. One planet is 2.3 times the mass of Jupiter, and the other is 1.57 times the mass of Jupiter. HD 20367 is a G0 type star, approximately the size of the Sun, with one orbiting planet. The planet, discovered in 2002, has a mass 1.07 times that of Jupiter and orbits every 500 days.

Credit: Constellation Universe Guide, Constellation List, Wikipedia.