The March night sky

By CLIVE JACKSON [email protected]

Clive Jackson is the Director of the Astronomical Observatory of Tavira (Sitio do Malhão, Tavira) and the Camera Obscura (next to the Castle in Tavira), specialising in education and public outreach.

Welcome to the March night sky. This is the month when the Sun moves into the northern hemisphere of the sky, and it marks the beginning of spring for us in Europe.

This is called the Equinox in astronomical terms, and signifies that for a short while around March 21, the day and night will be of the same duration.

Over in the west just after sunset the brilliant planet Venus can still been seen, but with each passing day this planet moves lower towards the horizon and by the middle of March is no longer easily seen. To compensate for this over on the eastern horizon just as it is getting dark we can see the ringed planet Saturn rising in the constellation of Leo. Unfortunately this year the rings are not well visible as the Earth is passing through the plane of the rings. This happens twice in every twenty-nine year period of Saturn’s orbit, and 2009 is one of those years. On March 10 the nearly full Moon will pass close to Saturn.

Four hundred years ago Galileo-Galilei looked at Saturn with his tiny homemade telescope and noticed something odd about the planet. He could not see the rings properly with his small instrument but he did notice that whatever was visible around Saturn changed from year to year. Along with the four giant Moons of Jupiter and the phases of Venus, Galileo’s discoveries changed our understanding of the night sky.

Modern telescopes are of much better quality than Galileo’s, but as Saturn’s rings are much more difficult to see in 2009 than they were in 1609 you could replicate Galileo’s view and see just how hard it was for him to understand exactly what he was seeing. His telescope magnified about thirty times and this should be enough to show the rings when the atmosphere is steady.

The Moon is at First Quarter on March 4, full on the 11th and Last Quarter on the 18th and New on the 26th.

Clive Jackson can be contacted by phone on (00351) 281 321 754, by fax on (00351) 281 324 688, or by email to [email protected]. To visit his website, click on the link to the right of this page.