On a certain date in the late spring/early summer, the Sun is observed to sit at

Question

On a certain date in the late spring/early summer, the Sun is observed to sit at a Right Ascension of 5 hours 0 minutes. The picture below is a bird's eye view looking down on the Solar System. The Sun is at the center with the spokes representing lines of sight along different lines of Right Ascensions on the celestial sphere. The solid inner circle is the orbital path of the Earth around the Sun, with four different possible positions of the Earth depicted. Which letter represents the Earth's position in orbit on the day the Sun is observed at 5 hours 0 minutes on the celestial sphere?

A

B

C

D

Not enough information is given

Explanation / Answer

Sun revolves along the line of ecliptic in an anticlockwise manner (seeing from north celestial hemisphere). At March/Vernal equinox, it is at 0 hr RA position and in early summer, sometime it sits at 5 hr RA position, as mentioned.

Now in actuality, earth moves around sun. So anticlockwise motion of sun (along ecliptic) around earch is equivalent to clockwise motion of earth about the sun.

Consecutive RA lines are separated by 1 hr. So Sun will be 5 RA lines eastward (anticlockwise) from the March/Vernal equinox position. So earth's position will 5 places clockwise from 0 position which will be position B.

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