Tuesday 7 July 2020

Astrognome A-Z of Constellations # 72 Sagittarius

Sagittarius the Archer
An ancient constellation depicting a centaur, half man, half beast with a raised bow and arrow. Sagittarius has been visualised this way since at least ancient Greek times. It probably originated with the Sumerian civilization around the river Euphrates who saw him as Nergal, their archer god of war.
It is an older constellation than the other celestial centaur, Centaurus and is different in character. Whereas Centaurus is identified as a scholarly beneficent creature, Sagittarius is depicted with a threatening look aiming his arrow at the heart of Scorpio the Scorpion.
The stars of Sagittarius are often depicted as forming a teapot while a ladle known as the Milk Dipper a suitable implement to dip into this rich region of the Milky Way. The centre of our galaxy lies in Sagittarius so that the Milky Way star field are very rich here.
The centre of the galaxy is marked by a radio source known as Sagittarius A near the border with Scorpios. The main attraction of Sagittarius are its nebulas and clusters. There are 15 Messier objects more than any other constellation.
The brightest star, epsilon also known as Kaus Australis which means the southern part of the bow has a magnitude of 1.8 and is a B9 giant star with a temperature of 9,500’C and lies 143 light years away.
Sigma or Nunki with a magnitude of 2.0 and lying 228 lihjy teras away. It is a B2 class star with a temperature of 18,500’C.
Delta at magnitude 2.7 is also know as Kaus Media which means the middle of the bow, its an orange K3 giant star with a temperature of 4,000’C and is 348 light years away.
Lambda or Kaus Borealis which means northern part of the bow has a magnitude of 2.8 and is an orange K0 star with a temperature of 4,700’C. It is 78 light years away.
Gamma of Al Nasl which means the point of the arrow is a magnitude 3.0 star lying 98 light years away. It is another K0 class star with a temperature of 4,600’C.
Alpha is only mag 4.0, its a B3 class star with a temperature of 12,000’C and is 182 light years away.
Sagittarius is home to M8 the Lagoon Nebula, M17 the Omega Nebula, M18, M20 the Triffid Nebula, M21, M22, M23, M24, M25, M28, M54, M55, M69, M70,and M75

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