Hubble Nebula (NGC 2261) in Unicorn - NGC 2261, Hubble's variable nebula - The Hubble...

Hubble Nebula (NGC 2261) in Unicorn - NGC 2261, Hubble's variable nebula - The Hubble Nebula is a weak nebulosite that surrounds the star R Monocerotis (R Mon), the bright star at the bottom of the nebula. The mass of the star R Mon is about 10 times that of the sun. It is approximately 2600 light years away and is only 300,000 years old. Image obtained by Siding Spring's 3.9m telescope. Hubble's variable nebula is in Monoceros and was the first object to be photographed with the famous 200 inch Hale Telescope at Palomar in 1948. This curious object is a reflection nebula in which is embedded the star R Monocerotis. Variations in the appearance of the nebula were noted by the American astronomer Edwin Hubble in 1916. They are probably caused by opaque clouds of dust passing between the hidden star and the outskirts of the nebula we see, the moving shadows changing the apparent form of the glowing dust in an irregular way. This picture was made from three AAT plates taken over several years and subtle colour changes around the edge of the nebula are indications of the variability