The Milky Way – our own galaxy –  is home to over 200 billion stars, one of which is our own sun, rotating around what is now thought to be a massive black hole at the centre.

September is a good month to view the band of the Milky Way, popularly known in Maltese as It-Triq ta’ Sant’Anna u San Ġwakkin, shortly after sunset. It stretches from the southern horizon to overhead and beyond. Head to a site that is as dark as possible as the faint light of the Milky Way is drowned out by exterior lighting.

Dwejra in Gozo and Miġra l-Ferħa, l/o Imtaħleb, Rabat, are two of the best locations. It is a sad fact that light pollution has destroyed the night sky; however, till now, you cannot miss it from any of these two locations. Next weekend is ideal as the moon will be new so there will not be any interference at all and a perfectly dark sky can be enjoyed.

For millennia, humanity has stared into the night sky and stood in awe of the Milky Way. However, today no one can see the 2,000 or more stars that are visible to the naked eye the way one used to in the past because light pollution has destroyed our night-time viewing pleasures.

When we look at the Milky Way we are witnessing a giant collection of thousands of millions of stars and dust clouds, not to mention thousands of other planets – some of which may, like the Earth, harbour life as we know it.

Astronomers estimate that the Milky Way is up to 120,000 light years across

The sheer size of this galaxy is mind-boggling. Astronomers estimate that the Milky Way is up to 120,000 light years across. This means that even if we were to travel at the speed of light (over a billion kilometres per hour) it would take all those thousands of years to cross from one end to another.

In the middle of galaxy itself there is a tightly-packed star mass known as the bulge. At the centre of the bulge astronomers have found an object which they called Sagittarius A*, a complex radio source thought to be a supermassive black hole, over four million times the mass of our sun. When we look towards the constellation Sagittarius we look in this direction.

In between the centre of the Milky Way and the Earth lies what is known as the interstellar medium – vast clouds of dust and gas that prevent us from seeing the bulge of the galaxy directly.

Looking at the Milky Way through a pair of binoculars will reveal myriads of stars. However this was not the case for astronomers of yesteryear who had no such instruments.

Aristotle, for example, believed that the Milky Way was caused by “the ignition of the fiery exhalation of some stars which were large, numerous and close together”, in the Earth’s atmosphere.

Persian astronomers, such as Nasr al-Din al-Tusi in the 13th century, postulated that the cause of the milky band in the sky was due to tightly clustered stars.

However, it was only when Galileo Galilei pointed his telescope towards the heavens in 1610 that the real reason was found. For the first time people realised there were many more stars in the skies than could be seen with the naked eye, and that all the stars we see in the sky form part of the Milky Way.

Years later, in 1755, Immanuel Kant also proposed that the Milky Way consisted of stars held together by mutual gravity. However, it was only in the 1920s that Edwin Hubble found out that other spiral objects in the sky were, in fact, other galaxies spread out in the universe. By doing so, astronomers could discover the true size and shape of the Milky Way and, ultimately, the scale of the universe around us.

In the western skies, planet Jupiter sinks slowly into the sunset and passes behind the sun on September 26. Mars and Saturn remain visible, but are setting mid-evening. Both are now less bright than they were earlier this summer, but they still outshine nearby star Antares in Scorpius, the scorpion.

Astronomical events during September

Sep 1: New moon.
2: Neptune opposition.
3: The moon close to Venus.
6: Moon apogee: 405,100km.
8: The moon close to Saturn.
9: First quarter moon.
16: Full moon.
18: Moon perigee: 361,900km.
22: Autumnsal equinox – Autumn starts in the northern hemisphere.
23: Last quarter moon.
26: Jupiter conjunction (behind the sun).

Alexei Pace is a member of the Astronomical Society of Malta.