DARK SKIES: Birthplace of our solar system?
OF THE many astro-related questions we get at the observatory, two stand out:
Q1. Why can't we see the Milky Way all year round, like we do in winter?
Answer: Draw a large circle with the centre dot to represent the centre of the Milky Way galaxy.
Now place a large dot two thirds out from the centre.
That's our sun. Now draw a small circle around that dot. That's Earth's orbit.
Now divide that circle into four equal parts.
At the 12 o'clock position, mark that A.
At the 9 o'clock position, B. At the 6 o'clock position, C and at the 3 o'clock position, D. On some paper, mark A for March, B for June C for September and D for December.
When the Earth moves around the sun between March and September, the Earth's shadow cast by the sun into space, points towards the centre of our Milky Way galaxy.
As we pass from September through to December to February, the Earth's shadow points towards the outer edge of the Milky Way.
That is why in summer we see Orion, Canis Majoris, Taurus, Pegasus, the Pleiades, and the bright stars, Sirius, Canopus and Archenar.
So between November and February at night, we're looking out to the edge of that big circle - the outer edge of the galaxy.
In Autumn then winter, we start to see the Milky Way strip climb higher into the night skies, and by August, it passes overhead.
Winter stars pass over during the day in summer and vice versa. T
hat is why we only see the Milky Way about seven months of the year.
Q2. If stars, moons and planets are born within clouds of dust and gas called nebulas, where did our solar system come from, when there is no such nebula close by?
Answer: The most plausible answer to that is after many years of astronomical research by astro-scientists using sensitive spectra, infrared, ultraviolet, x-ray and photographic equipment with space telescopes, many of them say it was the sun that helped formed the solar system.
While others say we may have come from the Orion Nebula - Messier 42, 1600 light years away, as it is the closest nebula to us in the Milky Way galaxy. So the jury is still out.
The Orion Nebula is best seen in the summer months, that lies in the 'handle of the Saucepan' In our large telescopes, the view is mind-boggling but you won't see colour.
We'll explain more about that next time. Within that huge cloud of dust, and gas, there are four stars called The Trapezium. Any one of them would light up our solar system trillions of times more, than our sun.
So next time you look up into that starry night sky, just think that out there, billions of other solar system we have yet to find, with possible intelligent life forms, could also be asking the same question.