Star Constellation Facts: Sagittarius, the Archer

Star Constellation Facts: Sagittarius, the Archer
Alexander Jamieson’s Celestial Atlas (1822)

Sagittarius (“archer”) is a zodiac constellation that contains an asterism of eight bright stars in its western region that stargazers refer to as “the teapot”, after the object it resembles. The brightest star in Sagittarius is Kaus Australis, a blue giant star located 125 light-years distant, and shining 375 times brighter than our sun. Since the constellation lies on the Milky Way, it is relatively easy to find, but in far northern latitudes, some of the constellation’s stars may be lost in the haze close to the horizon.

Location: A Southern Constellation

Sagittarius is a southern constellation that can be seen between latitudes +55° and -90°. It takes up a 867 square degrees area of the night sky, making it the 15th largest constellation, and can be found between Capricornus in the east and Scorpius to the west. The easiest way to then locate Sagittarius is by looking for the famous Teapot asterism that is made up of its brightest stars, and being positioned on the Milky Way also helps with the constellation’s identification. Alternatively, imagine a line line drawn through the star Deneb (Cygnus) onto Altair (Aquila), and prolonged a similar distance subsequently terminating in Sagittarius.

Best Seen: Autumn

From the northern hemisphere, Sagittarius is best seen during the months of August and September, which corresponds to spring in the southern hemisphere. However, from mid-northern latitudes, the constellation stays low in the south and never rises high in the night sky.

Mythology: Represents a Centaur

Sagittarius: The Archer

The constellation represents a centaur holding a bow aimed at the neighbouring constellation of Scorpius, which is represented by the red supergiant star Antares, at the heart of the scorpion. In Greek mythology, Centaurs were half man and half horse, and one of the noblest and wisest of this hybrid race was Chiron, who tutored many Greek legendary heroes, including Heracles, Achilles and Jason. Unfortunately, Heracles accidentally wounded the immortal Chiron with a poison arrow dipped in the blood of the Hydra who was then in such pain that he pleaded with Zeus to put him out of his eternal agony. After his death Chiron was placed among the stars on account of his noble life and deeds.

Shape: An Archer’s Bow or Teapot

It takes a lot of imagination to see a centaur holding a bow, but with some effort, it is possible to make out the shape of a drawn bow armed with an arrow, the bow being represented by the stars Delta (Kaus Media), Lambda Sagittarii (Kaus Borealis), and Epsilon Sagittarii.

Notable Stars: Kaus Australis (1st magnitude)

– Nunki (Sigma Sagittarii) is a 2.1 magnitude, hydrogen-fusing blue-whited dwarf star about seven times as massive as the Sun, and at least 3,300 times as luminous. It is also a very fast spinner, with a rotational velocity at its equator in excess of 200 km/sec, which is around 100 times as fast as the Sun. Nunki is about 228 light years away.

– Ascella (Zeta Sagittarii) is a 2.59 magnitude binary star system that lies at a distance of 88 light years, and whose two stars orbit each other once every 21 years.

Star Constellation Facts: Sagittarius, the Archer– Kaus Media (Delta Sagittarii) is the primary star in a 2.72 magnitude multiple star system about 306 light years away. The star is an orange giant that is about five times as massive as the Sun, 62 times as big, and at least 1,180 more luminous.

– Pistol Star (V4647 Sgr), one of the brightest stars yet discovered in the Milky Way, is a blue hypergiant located in a dense region of space near the center of our galaxy known as Quintuplet Cluster. This variable star is generally believed to be between 4 and 10 million times as bright as the Sun, and up to 200 times as massive meaning it produces about as much energy in 20 seconds as the Sun does in a full year. The star is located about 25,000 light years away, and is obsured by the intervening dust.

Notable Objects: Many Nebulae and Star Clusters

Sagittarius lies in the direction of the center of our Milky Way galaxy, and being in such a dense part of night sky is packed with many interesting astronomical objects worth observing, including several nebulae with colorful names, such as the Lagoon Nebula (M8), Omega Nebula (M17), and the Trifid Nebula (M20). The constellation is also home to the Sagittarius Cluster (M22) which at a distance of 10,600 light years away is among the closest large star clusters to Earth. Further objects of interest include Sagittarius A, which is a famous radio source; and an enormous cloud of molecular dust and gas called Sagittarius B2, which spans an area 150 light years in diameter, about 390 light years from the Galactic centre.

Meteor Showers: None

Despite diligent searches by thousands of observers over many years, no meter showers that emanate from radiants in Sagittarius have ever been identified.

Planets: 25 Stars with Planets

Of the 25 stars with planets in the constellation, one has two planets, with the rest having one planet each. However, no star in the constellation has a planet in its habitable zone, although there are two potentially habitable moons.

Astrology: Nov 22 to Dec 21

The Sun currently passes in front of Sagittarius between December 18th and January 20th, which is off by around one month from the horoscope date of November 22st to December 21st. A distinguishing feature of Sagittarius is that the Sun shines in front of this constellation on the December 21st winter solstice.

Date of Birth: Nov 22 to Dec 21
Sign Ruler: Jupiter
Element: Fire
Birth Stone: Amethyst
Metal: Tin
Color: Light Blue
Characteristics: Insightful, rational, brave, lively, optimistic
Compatibility: Virgo, Leo, and Aries