NOW the winter solstice has passed, the daily overhead passage of the sun is creeping south as we near spring.
The sun’s increasing strength (radiation) as it appears to climb higher, happens because it has much more of Earth’s atmosphere to penetrate when it is low to the north, compared with when it is high overhead in summer.
We all experience this power that heats the upper parts of your car, the paving under your feet and sands of the beaches, making them too hot to touch or walk barefoot on at times. Also, during the summer, the sun’s residual energy remains in all the paving and countryside which means any rain or moisture soon evaporates into the air.
By mid July, this return movement is approximately four sun diameters (two degrees) south from its shortest-day position and this subtly increasing radiation is about to trigger the wonders of the explosion of the spring growth. All this is due to the Earth’s 23.5 degree tilt as it orbits the sun. This results in the 47 degree difference in the sun’s position from the shortest day to the longest in our southern hemisphere.
In the night sky, facing north, the receding Jupiter, now 5.508 astronomical units (one AU is Earth-Sun distance) appears to the north west now and has company with the brighter stars Spica and Arcturus. Over to the north east, the extent of the Milky Way extends across to the the horizon. There are two brighter stars low down, Vega in Lyra and further east and a bit higher, Altair in Aquila.
Now, to the south east, there is no mistaking the great constellation of Scorpius, (Maui’s Fish Hook), with the giant red star Antares in its body, climbing now towards its highest point in the sky. Trailing behind Antares and easy to find comes Saturn, at 9.177 AU and now in the best period to view its beautiful and unique ring system.
Below the sting of Scorpius, in Sagittarius is the unmistakable glow of the hub of our own galaxy which contains from 100 to 400 billion stars in total, of which, by far the greater number are the main sequence stars, similar to our Sun.
Astronomers, by observing the various wave lengths of light emitted from thousands of stars, have been able classify them into the various categories with great success.
We, in the southern hemisphere, are so lucky in that we get this best possible view of our Milky Way and its centre during the winter months. Our visitors from the light-polluted cities in the north are in awe of such a spectacle. The Whakatane Observatory, was opened in 1964, the first and most accessible in the Bay of Plenty, and has had many thousands visit the facility in its 53 years.
The Mount John Observatory, Tekapo, was opened in 1965 as more of a professional facility. But since, as a result, the Aoraki McKenzie Dark Sky Reserve has been designated, internationally, as one of the best places in the world for its dark night sky, and as a result has become a major tourist attraction.
More recently, Great Barrier Island has also been also recognised for its dark skies. This will no doubt greatly enhance the island as a tourist attraction and is a matter our district council needs to be aware of and be more proactive in reducing the light pollution here, as we already have a well-established facility in operation.
To the south, the Southern Cross is now descending as it circles around the South Celestial Pole, while opposite , through the long axis, star Achernar is swinging left and clearing the horizon once again. The Magellanic Clouds are either side of due south, with the small cloud to the east. Giant star Canopus (also called Alpha Carinae or The Keel) is also nearing the south-west horizon. It, and all the fore-mentioned, are classed as circumpolar stars, meaning they never set due to their proximity to the celestial pole. Certainly, this is true further south, but we lose it for a while due to the high ranges in our southern hinterland.
The glorious extent of the visible part of our Milky way now extends from the north east, right across to the south west and is such a great spectacle to observe. The latest estimate is that our galaxy is just one trillionth of the total number of galaxies there are, based on the current observations of all the latest very large telescopes, both land-based and orbiting in space.
In the morning sky, there is no mistaking the brilliant Venus (1.093 AU), soon to become lost behind the glare of the rising sun before appearing in the evening sky once more. Venus is in company with Pleiades (Matariki). Tauris, with bright star Aldebaran and the unmistakable Orion are all worth taking taking in on a clear, July morning before sunrise.
A reminder too, that although Venus appears very bright in the sky, it, like the Moon and other visible planets, is only reflecting a the blinding light from our sun, the nearest star, and should not to be confused with all millions of bright objects visible on a dark night.
By far the greater proportion are intensely bright nuclear furnaces, all at varying and tremendous distances in the great vault of space, making them visible to us all from our tiny pale-blue dot, floating in the vastness of space.