Archive for April, 2012
April 15 saw Saturn reach opposition. Saturn now rises at sunset, is visible the whole night, and is also at its brightest. Great telescopic views await us in the coming weeks. Of course, Saturn is famous for its rings and people expect to see them when looking through a telescope. However, the orientation of the rings changes due the tilt of Saturn’s rotation axis and its travel around the Sun relative to the Earth. Occasionally the rings seem to disappear as we see them perfectly edge on. Fortunately, from our perspective the orientation is currently tilted and the next few years promise great views of the rings.
On April 15, 2012 we mark the 100th anniversary of the sinking of Titanic. There is a fascinating article on astronomical connections to this event in Sky & Telescope magazine which you can read here:
The article discusses two connections in particular. It points out that there was no Moon in the sky the night the ship struck the iceberg. If there had been, water breaking around the base of the iceberg would have been easier to spot. The second is even more interesting in that it suggests the sinking may be related to a rare confluence. Ocean tides are due to the gravitational influence of the Moon and Sun. When the Moon and Sun line up at new and full Moon we have the so-called spring tides (completely unrelated to the season) which are larger than normal tides. During certain times of the year, the spring tides coincide with the Moon being at perigee, or its closest approach to the Earth, resulting in even larger tides called perigean spring tides. In January of 1912, the perigean spring tides also coincided with the Earth being at perihelion, or its closest approach to the Sun. This ideal gravitational alignment for producing large tides may have contributed to an unusually large number of icebergs in the north Atlantic in April by helping to float grounded icebergs along the coasts of Labrador and Newfoundland which would then have continued their journey southward.
Orion is easy to find above the west-southwest horizon after sunset this time of year. That it is so instantly recognizable makes it a useful guide for other night sky features. Follow Orion’s belt eastward and you will find the bright star Sirius in the constellation Canis Major (from the Latin for greater dog – can you spot the dog?). The upper two stars of Orion (Betelguese and Bellatrix) that form his right and left shoulders point eastward to another bright star, Procyon in the constellation Canis Minor (from the Latin for lesser dog – with only two stars in this constellation, you’ll have to use your imagination to see the dog). Sirius, Betelguese and Procyon form a nice equilateral triangle of stars called the Winter Triangle. Above the Winter Triangle you should easily spot the two brightest stars in the constellation Gemini (the twins): Castor and Pollux.