Thursday, 25 July 2013

Gulf Stream and Star Watching

Thursday July 25th, 40.8N, 57.7W

The ocean around us today has changed from the green and rather forbidding cold, foggy ocean of the Labrador Current to the warmer, indigo blue colours of the Gulf Stream.   A fresh wind is blowing, but we have clear blue skies and a beautiful blue sea.  The depth under our keel is 5000 m, deeper than at any other point in this journey, as we pass within 200 nautical miles of Sable Island, Canada, a small, narrow crescent-shaped sand island around 13 square miles in size and home to only a handful of people.  We’re now 2408 miles from Southampton, with only 745 miles to run to New York on a straight line.  The Commodore describes this area as the region of strongest hydrographic contrast in the world, as the ocean temperature has changed by 10 degrees from the cold arctic currents of yesterday to the warm Gulf Stream today.  But the Gulf Stream itself is complex and inconsistent, with whorls, eddies, gyres all changing the speed and temperatures as we make our passage, and showers and squalls are expected for this evening.  We can also spot brown clumps of weed floating in the open ocean, Sargasso weed from the Bahamas being pushed north by the Gulf Stream and appearing like brown clumps of grapes in the seawater.

It is this changeable weather that has prevented us from hosting star parties from the upper deck on this particular crossing – the entertainment folks need time to advertise these events, and rely on weather forecasts.  The full moon and long summer days also mean that conditions are best late at night, when they want to minimise disturbance to guests.  That said, I’ve been doing my best to point out to interested guests Venus on the western horizon after sunset; the summer triangle (Deneb, Vega and Altair; in Cygnus, Lyra and Aquila); star hopping from the Plough to Polaris, Arcturus and Leo; as well as Cassiopeia and her entourage east of North at 10-11 pm (Cepheus, Andromeda, Perseus, etc.).  The great square of Pegasus should be on the horizon to the northeast.  Saturn is a good object for viewing in the early evening too towards the South West in the Constellation Virgo; and Jupiter is rising just before dawn.  We’ll talk about all of these in Fridays’ live planetarium shows, but please do stop me to ask me if you’re out on the upper deck this evening!

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