We
all have learnt that earth while going around the sun in an elliptical
orbit comes closer and goes farther away from the sun and in an year
during its orbit, we have two days perihelion (earth being closest to
Sun) and Aphelion (Earth being farthest away from the sun).
So that in layman's term means we should see Sun slightly bigger on the day of Perihelion day and slightly smaller on the Aphelion day (as compared to average distance what we call as the 1 Astronomical Unit). To put that to visual understanding, I clicked one image of the sun near Aphelion day on 6th July (though 4th July was Aphelion day but clouds did not permit me to click the sun, anyways in 2 days earth hasn't moved much as far as astronomical distances are concerned) and my next target is to click it on Perihelion day on around 3-4 January and then compare the size of the sun's image. While searching through my archives, I found that I clicked few pics of sun during December last year with same set of equipment. That was on 1 December, 2013. So I tried comparing these two images just to get a visual idea as how much the difference is there. You can have a look at the combined image and see how big and small sun looks while being at perihelion and aphelion. It is quite a visual treat to see the difference, and also a nice tool to teach our educators and students as how and why we have longer total solar eclipses in July and not in January!! Well that's another point to ponder about!!
So that in layman's term means we should see Sun slightly bigger on the day of Perihelion day and slightly smaller on the Aphelion day (as compared to average distance what we call as the 1 Astronomical Unit). To put that to visual understanding, I clicked one image of the sun near Aphelion day on 6th July (though 4th July was Aphelion day but clouds did not permit me to click the sun, anyways in 2 days earth hasn't moved much as far as astronomical distances are concerned) and my next target is to click it on Perihelion day on around 3-4 January and then compare the size of the sun's image. While searching through my archives, I found that I clicked few pics of sun during December last year with same set of equipment. That was on 1 December, 2013. So I tried comparing these two images just to get a visual idea as how much the difference is there. You can have a look at the combined image and see how big and small sun looks while being at perihelion and aphelion. It is quite a visual treat to see the difference, and also a nice tool to teach our educators and students as how and why we have longer total solar eclipses in July and not in January!! Well that's another point to ponder about!!
For those who are technically aligned, here are the numbers to play with during the days i took the image
Canon 500D, 250 mm FL
On 6th July, 2014:
earth distance from Sun: 1.017 au or 152.1 million kms
Apparent Size of Sun: 31 arc min 26 sec
On 1 December, 2013
Earth distance from sun: 0.9859 au or 147.5 million kms
Apparent Size of sun: 32 arc min 25 sec
On 1 December, 2013
Earth distance from sun: 0.9859 au or 147.5 million kms
Apparent Size of sun: 32 arc min 25 sec
So we have almost 1 arc min difference in apparent dia of Sun
Have a look at the image and enjoy!!
Written by CB Devgun, President, SPACE Foundation
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