Another Destination? Another Sky!
23 07 06
Still planning a trip this summer? Interested in a new night sky? If you answered "yes" to both of these questions, this column is for you.
The only way you will not get a new sky when traveling is to make sure you end up on the exact same latitude as you started. For example, if you are going from San Diego to, let's say, the vacation hot spot of Esfahan, Iran, your sky will be exactly the same.
Why? Merely moving directly east or west on the same latitude does nothing to your sky. The only difference you'll notice is that the sun rises sooner or later, which is nothing to write home about.
But will you be traveling north or south? Then part of your travel plans might include looking up and celebrating the difference. Allow me to try to explain why.
Use your mind's eye and see the planet spinning around like a top. Someone standing on that fat line around the middle called the equator gets to see the entire sky over the course of a day. Of course the sun interferes during the daytime, but the fact remains: That person's view sweeps around the entire heavens like a light in a lighthouse.
Sadly, some freezing chap at the North Pole essentially stands in one place and, through a 24-hour period, makes one very slow pirouette. But that poor gentleman only gets to see the northern part of the heavens, what is called in astrospeak the North Celestial Sphere. The whole southern part of the sky is blocked by a big rock, what is called in astrospeak the Earth.
One standing on the South Pole has just the opposite problem. But only the southern stars are visible from there. No North Star, no Big Dipper, no Orion. Our big rock blocks them all.
Those are the extremes. Now, for more realistic examples.
If you are traveling north on your vacation, you are getting closer and closer to our frozen friend on the North Pole. Your skies will start looking more and more like his.
The southern constellations like Sagittarius and Scorpius will begin to disappear below the horizon. The stars will rise and set at sharper and sharper angles. The North Star, Polaris, will be suspended higher and higher above your head.
In fact, you can use Polaris to judge approximately how far north you have gone. We who live around San Diego hug the 32nd parallel. For a skywatcher that means that the North star, Polaris, is about 32 degrees above the horizon.
If we traveled to Vancouver, British Columbia, at 49 degrees of latitude, the North Star at night would be - you guessed it - 49 degrees above the horizon.
Go all the way to the North Pole and Polaris is now directly above your head.
And on the Pole the stars don't rise or set. What? They travel about a winter sky in vast sweeping circles around the observer's head. There is a paradigm shift that would take time getting used to! (The sun blots out the stars during northern summer.)
Travel south and things change, as well. The North Star sinks lower and lower toward the horizon. The stars look more and more like they are rising straight up out of the eastern sky like fireworks before the blast.
If you travel to the equator itself Polaris is all the way down on the horizon, and you will, over the course of a year, see all 88 constellations.
Of course traveling further south will afford you a better view of all those southern constellations, and the northern ones will begin to disappear below horizon.
But two things will become noticeably clear to a careful observer. One is that there is no South Star, no Polaris of the southern skies. People living "down under" must use a group of stars to figure out direction and latitude.
And the stars rise and set in a strange fashion for our eyes. Instead of rising in the east and sweeping an angle over the southern skies to set in the west, stars will rise in the east and cut out a swatch of sky northwards to set in the west.
Wherever you go, take some time from your busy vacation schedule, go outside and look up. There may be a whole new heaven awaiting you.