THE SOUTHWORTH PLANETARIUM
207-780-4249   www.usm.maine.edu/planet
70 Falmouth Street   Portland, Maine 04103
43.6667° N                   70.2667° W 
Altitude:  10 feet below sea level
Founded January 1970
Julian Date: 245891.16
                  "I don’t know what you could say about a day in which you have seen four beautiful sunsets."   -John Glenn

THE DAILY ASTRONOMER
Tuesday. February 11, 2020
Thor's Helmet

Today, why don't we stop right here:

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We are nearly 12,000 light years from home as we behold Thor's Helmet through our port side window.  That spectacular sight is a 30 light year wide emission nebula well concealed within the constellation Canis Major.  Known prosaically as NGC 2359, this emission nebula consists of a large bubble tipped on either side by towering filaments, hence the mythological moniker.  Deeply embedded within this gaseous envelope one would find a rare and ultra hot Wolf Rayet star.   With surface temperatures between 30,000 - 210,000 K, such stars are much hotter than most others.      Such temperatures result in extremely high luminosities: tens or hundreds of thousands of times more energetic than the Sun.  They are also highly evolved stars that have depleted their outer hydrogen and are in the process of fusing helium or other heavier elements.  

Such stars are losing their matter at a prodigious rate, hence the turbulence of the gases comprising the Thor's Helmet nebula.   Estimating the mass loss rate has enabled astronomers to approximate the nebula's age at about 73,000 - 230,000 years.   With the matter expanding at more than 10 kilometers per second, the nebula will persist for hundreds of thousands of years more as the gases slowly dissipate.  During that time, of course, the gas dynamics within the filament will alter the structure substantially and its resemblance to the Norse god's headwear will fade.

At the moment, though, we can see the ionized gases exuding an array of vibrant colors all along Thor's Helmet currently expanding in the deep darkness of our home galaxy.






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