Star Constellations in Stellarium
Misconceptions about star rotation in southern locations
Stellarium is an online application in which you can view the stars.
Go to stellarium-web.org
You can select different viewing locations and times and see for yourself what the constellations look like from different locations on earth.
A common misconception is:
“the stars rotate in the opposite direction in southern locations”.
This is silly! Of course the sun, moon, stars and everything in the sky rotates from East to West no matter where you are on earth. So the statement that stars rotate in the opposite direction in southern locations is a false statement. You can prove this for yourself in Stellarium.
In Stellarium, select a southern location such as Auckland New Zealand by clicking on the location map on the lower left of the screen. A map will pop up and you can select any location on earth.
You can set the viewer to face North by placing the ‘N’ in the centre of the the viewer.
You can view the constellation names by clicking on the “constellation” icon on the bottom centre, and you can view the constellation pictures by selecting the “constellation art” icon next to it.
There is also a date and time pop-up on the lower right side of the screen.
By advancing the time using the slider on the date & time pop-up, you can watch how the stars rotate across the sky throughout the night.
Question: As you advance the time by using the time slider, which way do the stars rotate?
Answer: the stars rotate East to West, of course!
They appear to rotate counter-clockwise when facing North!
Now set the viewer to face South, by sliding the constellation viewer map so that the ‘S’ for South is in the centre of the viewer.
As you advance the time by using the time slider, which way do the stars rotate?
Answer: again, the stars rotate East to West
However, now they appear to rotate clockwise when facing South!
Now change your location to a Northern location, like San Diego, for example.
Now repeat the same steps. First set the viewing direction to face North by placing the ‘N’ in the centre of the viewer, then advance the time slider and watch the constellations rotate across the sky.
Next set the viewing direction to face South, by placing the ‘S’ in the centre of the viewer and advance the time slider again to watch the constellations rotate across the sky.
Question: As we advance the time, which way do the constellations rotate for each direction we face?
Answer:
When facing either North or South, the stars rotate East to West, of course!
However,
When facing North, the direction appears counter-clockwise
When facing South, the direction appears clockwise!
Question: Is there any difference between North and South locations?
Answer: NO!
There is no difference in rotation direction of Northern and Southern locations.
From every location on earth, the sky rotates from East to West
AND from any location…
the sky appears to rotate counter-clockwise when facing North;
and the sky appears to rotate clockwise when facing South!
So it is a common misconception to say: “the stars rotate in the opposite direction in southern locations” THIS IS A FALSE STATEMENT!
Summary:
Northern location facing North = counter-clockwise
Southern location facing North = counter-clockwise
Northern location facing South = clockwise
Southern location facing South = clockwise
But did you notice something else?
The constellations are different! Why?
Now change the dates by advancing the date at the bottom right corner pop-up box.
Set New Zealand to a Spring month; and set San Diego to a Fall month
Set New Zealand to a Winter month; and set San Diego to a Summer month
What happens to the constellations?
Answer: The constellations appear in opposite seasons!
Another often heard statement:
“The constellations appear upside down in southern locations.”
Is this statement True or False?
See if you can answer this question by testing it out yourself in Stellarium
The answer is FALSE!
We can follow the constellations in each location to see for ourselves, for example:
Follow Virgo— she comes up in the East head first (right side up) advances across the sky throughout the night and then sets in the West head first (upside down).
Follow Pegasus— Pegasus the horse gallops across the sky, right side up, facing East.
This is the case no matter which location you are viewing from, it is the same configuration, there is NO Difference! Yes, Virgo goes from right side up to upside down by the end of the night, but this happens the same way in each location!
What else can you see that is different?
For example, are there any constellations not visible from different locations?
Do the constellations appear higher or lower in the sky in different locations?
Why is there so much confusion, and why are there misconceptions?
How the stars appear to rotate just depends which direction you are looking, the location on earth doesn’t make any difference.
Here’s an experiment you can do to prove this to yourself:
Get a toilet paper roll or paper towel roll
Cut out two circles and attach a circle to each end of the roll
Hold the roll in front of you and rotate it away from you
Now watch the circle disk on the right side, it is rotating counter-clockwise
Now watch the circle disk on the left side, it is rotating clockwise!
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