Tuesday, 17 November 2020

Astrognome 100 Great Stars No 74 Rho Ophiuchus


Rho Ophiuchus

If you don’t live in the southern hemisphere and cannot see Acrux in the constellation of Crux the Southern Cross then take a look at Rho Ophiuchus it’s more northerly clone. Rho at magnitude 4.6 is not as bright as Acrux at magnitude 0.8. the rho Ophiuchus system is made up of two blue stars which take around 2,000 years to orbit each other.

Rho lies at a distance of 380 light years and lies within a complex of bright and dark nebulae. The Rho Ophiuchus dark cloud is located just north of Antares in Scorpius. Rho is surrounded by IC 4604 a reflection nebula similar to that which surrounds Merope in the Pleiades. The letter IC stand for the Index Catalogue of clusters and galaxies that was stared in 1895.

IC 4604 is around 10 light years across and is the illuminated part of a nest of thick dark, dusty clouds. The dust blocks a large amount of light from rho reaching us and if not for the dust rho would be seen as a star of magnitude 2.0. Inside these clouds of gas are many proto stars that are in the process of forming into proper stars. Although with our eyes we can only seen rho we do know what is going on in the clouds around this star.

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