THE SOUTHWORTH PLANETARIUM
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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:

[image: 39583527365_6d8305f6af_b.jpg]


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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