Sun so close yet so cold...Yes Today Sun and earth will be closest to each other at a distance of 14,70,99,586 km. This point of any object closest to Sun is called Perihelion. The reason for the cold in northern hemisphere is due to the orientation of earth's axis and as you can see in the illustration, the Sun is moved to southern hemisphere where they are experiencing Summer now.

Since earth's orbit is almost circular, at farthest point from Sun which occurs on July 6th the distance will be 15,20,96,155 km. This farthest point from Sun is called Aphelion.
The angular size of the Sun which we measure in degrees at perihelion is 0.542018074degrees. And as we know the orbit is almost circular the difference in angular diameter of Sun from Perihelion to Aphelion is very small. At Aphelion the angular diameter is 0.5243709741degrees.

If we compare this to Mercury, the perihelion distance is 46,000,000 and this gives the angular diameter of Sun Seen from Mercury at 1.73434325degrees. The Aphelion distance of Mercury is 69,820,000 and this gives the angular diameter of Sun as seen from Mercury at 1.14247784degrees, almost half a degree difference. You can compare this to earth and Sun.

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ReplyDeleteSir,

ReplyDeleteI hv a 11 yr old child who is very interested in astronomy.Can she become a member of abaa?I need someone to give her proper guidance.do let me Know how we can contact abaa.

Thanks

Smitha

Hi, Very happy to know your daughter's interest In Astronomy at this young age. We meet every Sunday at Planetarium from 5:30pm. You can come and join our activities on Sunday evening.

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Ravi

Hi.. Does the club meet every Sunday evening? What are the membership fees??

ReplyDeleteABAA meets every Sunday from 5:30pm at Planetarium Bangalore. You can come on any Sunday evening and take part in the activities. There is no charge for attending the activities.

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