Equuleus is a constellation whose name is Latin for ‘little horse,’ a foal. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy. It is the second smallest of the modern constellations (after Crux), spanning only 72 square degrees. It is also very faint, having no stars brighter than the fourth magnitude.
Equuleus, the foal, seen next to the head of Pegasus in Johann Bode’s Uranographia (1801).
[http://www.ianridpath.com/startales/equuleus.htm]
In Greek mythology, one myth associates Equuleus with the foal Celeris (meaning ‘swiftness’ or ‘speed’), who was the offspring or brother of the winged horse Pegasus. Celeris was given to Castor by Mercury. Other myths say that Equuleus is the horse struck from Poseidon’s trident, during the contest between him and Athena when deciding which would be the superior. Because this section of stars rises before Pegasus, it is often called Equus Primus, or the First Horse. Equuleus is also linked to the story of Philyra and Saturn. Created by Hipparchus and included by Ptolemy, it abuts Pegasus; unlike the larger horse it is depicted as a horse’s head alone.
In Chinese astronomy, the stars that correspond to Equuleus are located within the Black Tortoise of the North (Běi Fāng Xuán Wǔ).
You’ll find Equuleus wedged between Pegasus’ nose, marked by the star Enif, and another small but better known constellation, Delphinus.
[https://bestdoubles.wordpress.com/2010/11/17/horsing-around-in-equuleus-delta-%CE%B4-%CF%832786-%CF%832765-%CE%B270-and-lamda-%CE%BB/]
Major stars in Equuleus include:
Kitalpha (Alpha Equulei) is a spectroscopic binary star of the spectral type G0III. It has a visual magnitude of 3.92 and is approximately 186 light years distant. It is the brightest star in Equuleus. The star’s name, Kitalpha, is derived from the Arabic phrase ‘qiṭ‘a(t) al-faras’ which means ‘a piece (or section) of the horse.’ Kitalpha is about 75 times more luminous than the Sun and has 2.72 times the mass.
Delta Equulei is another binary star in Equuleus. The components in the system belong to the spectral classes G0 and F5 and have visual magnitudes of 4.49 and 5.4. The system is approximately 60.3 light years distant from the Sun and has a combined apparent magitude of 4.47.
Gamma Equulei, or 5 Equulei, is also a double star. It belongs to the spectral class A9 Sr Eu. It has a visual magnitude of 4.7 and is 118 light years distant. Gamma Equulei is a chemically peculiar star that undergoes occasional variations in brightness and is also classified as a roAp star, or a rapidly oscillationg Ap star. (An Ap star is a peculiar star of the type A that shows an overabundance of certain metals and usually rotates much slower than regular A type stars.) The companion star has an apparent magnitude of 9.05 and is located 1.26 arc seconds away from the main component.
Beta Equulei is a main sequence star belonging to the spectral class A3V. It has four visual companions that are not physically related to the main star. The system has a combined apparent magnitude of 5.159 and is about 360 light years distant from Earth.
Epsilon Equulei is another multiple star in Equuleus. It consists of four components. It has a visual magnitude of 5.3 and is 196.4 light years distant from the Sun.
Lambda Equulei is another binary star in the constellation. The primary component in the system is a main sequence star belonging to the spectral class F6V. The system has an apparent magnitude of 6.72 and is approximately 332 light years distant from the solar system.
HD 200964 is a subgiant of the spectral type K0 IV. It has a visual magnitude of 6.64 and is some 223 light years distant. The star is notable because two large extrasolar planets were discovered in its orbit in July 2010. The planet closer to the star is almost double the mass of Jupiter, while the more distant planet is slightly less massive than Jupiter. The inner planet has an orbital period of 614 days and the outer one orbits the star every 825 days. This adds up to a 4:3 resonance: every time the bigger planet orbits the star four times, the smaller one orbits the star three times.
Deep sky objects in Equuleus include:
NGC 7015 is a galaxy with a visual magnitude of 12.4. It is 2.0′x1.8′ in size and about 212 million light years distant.
NGC 7040 is a spiral galaxy with an apparent visual magnitude of 14.0. Its coordinates are 21h 13m 16.5s (right ascension), +08°51′53.2 (declination).
NGC 7045 is a binary star in Equuleus. It was discovered by John Herschel in July 1827 and included on the list of NGC deep sky objects. It has a visual magnitude of 12.0.
NGC 7046 is a barred spiral galaxy 1.9′x1.4′ in size. It has an apparent visual magnitude of 13.10. The galaxy was discovered by William Herschel in October 1790.
[http://www.constellation-guide.com/constellation-list/equuleus-constellation/]
[https://en.wikipedia.org/wiki/Equuleus]
No comments:
Post a Comment