The Sagitta Constellation

Sagitta is a dim but distinctive constellation in the northern sky. Its name is Latin for “arrow,” and it should not be confused with the significantly larger constellation Sagittarius, the archer. Although Sagitta is an ancient constellation, it has no star brighter than 3rd magnitude and has the third-smallest area of all constellations (only Equuleus and Crux are smaller). It was included among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations defined by the International Astronomical Union. Located to the north of the equator, Sagitta can be seen from every location on Earth except within the Antarctic circle. Covering 79.9 square degrees and hence 0.194% of the sky, Sagitta ranks 86th of the 88 modern constellations by area. It is bordered by Vulpecula to the north, Hercules to the west, Aquila to the south, and Delphinus to the east. The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of twelve segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 18h 57.2m and  20h 20.5m, while the declination coordinates are between 16.08° and 21.64°.

Johann Bayer gave Bayer designations to eight stars, labelling them Alpha to Theta. What was viewed by Bayer, Friedrich Wilhelm Argelander and Heis as a single star Theta was, in fact,  three stars, and was now equated to HR 7705. In his Uranometria, Bayer depicted Alpha, Beta and Epsilon Sagittae as the fins of the arrow. Moreover, known as Sham, Alpha is a yellow bright giant star of spectral class G1 II (with an apparent magnitude of 4.38, which lies at a distance of 430 ± 10 light-years from Earth. Originally 4 times as massive as the Sun, it has swollen and brightened to 20 times its diameter and 340 times its luminosity. Furthermore, of magnitude 4.38, Beta is a G-type giant located 440 ± 20 light-years distant from Earth. Epsilon Sagittae is G8 III, 5.66m, multiple stars (four components; component B is optical) Ptolemy saw the constellation’s brightest star Gamma Sagittae as marking the arrow’s head, while Bayer saw Gamma, Eta and Theta as depicting the arrow’s shaft. Gamma Sagittae is a red giant of spectral type M0III, and magnitude 3.47. It lies at a distance of 258 ± 4 light-years from Earth. Eta Sagittae is a star of spectral class K2 III with a magnitude of 5.1, which belongs to the Hyades Stream. Theta Sagittae is a multiple star systems

Messier 71 is a very loose globular cluster mistaken for quite some time for a dense open cluster. It lies at a distance of about 13,000 light-years from Earth and was first discovered by the French astronomer Philippe Loys de Chéseaux in the year 1745. The Necklace Nebula is a planetary nebula in Sagitta. It is approximately 15,000 light-years distant   from the solar system. The nebula was discovered in 2005. The Necklace Nebula was created when a giant star came too close to its binary companion and exploded, producing the nebula. M1-67 is a nebula formed by expelled material from the Wolf-Rayet star WR 124. It is almost six light-years across   and expanding at a rate of over 150,000 km/h (100,000 mph), with an estimated dynamical age of 20,000 years. WR 124 is one of the fastest known runaway stars in the Milky Way, with a radial velocity of about 200 km/s. The star was discovered by the American astronomer and spectroscopy pioneer Paul W. Merrill in 1938. It is classified as an eruptive variable with a range of 0.08 magnitudes. The star’s estimated age is only 8.6 million years. Its initial mass was likely around 25 solar masses, but was now only nine solar masses because the star has blown off a large portion of its material. WR 124 lies at a distance of 10,900 light-years from   Earth and has a luminosity of 150,000 times that of the Sun. The star’s mean apparent magnitude is 11.50. IC 4997 is a planetary nebula in Sagitta. The nebula has a visual magnitude of 11 and lies at an estimated distance of 8,000 light-years from   Earth. It expands at a rate of 20 km/s. The nebula is believed to be very young, formed less than 700 years ago. NGC 6886 is another planetary nebula found in the constellation. It has an apparent magnitude of 11.8. The nebula’s distance is unknown, but estimated to be in the range from 4,900 to 17,900 light years. NGC 6886 was discovered by the English astronomer Ralph Copeland on September 17, 1884. Credit: Constellation Guide, Wikipedia.