Blue skies looking at me
March has none of the planets visible to the naked eye in the night sky
Let me begin by introducing you to a gentleman some of you may already know – ROY G BIV. Actually, this is a mnemonic to help us remember the colours that make up white light or the colours of the rainbow. Red – Orange – Yellow – Green – Blue – Indigo – Violet.
So, what does this have to do with why the sky is blue? We see the sun as basically white, though we must not look at it to confirm this. But this “white” light is actually a combination of all the colours as above.
Really? Well, you can test this by hanging a Smile Maker or prism in the window on a sunny day and – wow – ROY G BIV! The white light gets “bent” by the prism and the different colours in the white light are bent to different amounts – they are broken up. This is exactly the same process that occurs when we see a rainbow.
To show you how refraction or bending of light occurs, take a glass of water, add several drops of milk until it becomes cloudy. Now shine a flashlight through it. Look from one side, or 90 degrees, from where the flashlight is, and you should see a slightly bluish cast.
If you now look from the opposite side, from the flashlight, thus looking into the flashlight, you should see a little more reddish hue. The blue has been bent more and comes out the side where you looked first.
Now, as we know, our earth has an atmosphere, thank heavens. As the sunlight arrives from the sun, the molecules, or tiny particles of the gases in our atmosphere, do the same.
But there is a difference. For reasons I won’t go into, the blue portion of the white light is bent to degrees which causes it to bounce from one molecule of gas to another.
It literally gets scattered all over the sky and when it finally arrives at our eye, it appears to be coming from all over the sky. Thus, the sky looks blue.
Well, wait a minute. What about all the other colours? Well just as with the Smile Maker, just at the edge of the spectrum, reddish light is bent to a lesser degree and tends to come straight through the atmosphere.
It is not scattered all over. It’s a little different at sunset, but that is a thicker or longer atmosphere story. Violet? It’s actually bent more, but there is not that much in sunlight, so we really don’t see it. There, the sky is blue. Well, why isn’t it blue on the moon? No atmosphere and we need an atmosphere to scatter the sunlight, so we see bright sun and black sky.
What about Mars? Well, there, the sky is slightly reddish. Why? The atmosphere is much thinner than ours – not enough to cause significant scattering and the slight reddishness is caused by small iron oxide or rust particles in the air.
I love our blue sky.
So, what is in our sky this month?
Usually, I discuss the evening – night sky first and then the morning or predawn sky and the planets at each time.
Well, this month there are none of our usual planets in the night sky. One planet – Uranus – is there, but it’s a binocular or telescope object, and not usually for our description.
If you wished to look, you can use a Sky Map and try and locate some of the constellations that are currently in the sky.
Now morning – predawn, and it’s glorious. Firstly, we will be looking towards the east where all sky objects rise.
Venus is first. It currently rises about two hours before sunrise – glorious in all its brilliance.
About a half-hour later, Mars rises, much dimmer and more reddish than brilliant Venus. Next will come Saturn, also dim and further east.
Finally, at this early point of March, we can also see Mercury, a little lower and to the right of Saturn. However, Mercury is descending and soon disappears from view. Late in the month, Jupiter arises, but very low, and difficult to see in the east.
The spring (Vernal) Equinox occurs just after noon Atlantic Daylight Time on March 20. Don’t forget the Zodiacal Light which we described last month. Remember that you need a dark, light-free sky to see this.
• New Moon - March 2
• Full Moon - March 18 See you next month.