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Image of the Week: The Earth’s orbit around the Sun

19 Jun, 2015

V0025017 Astronomy: a diagram of the Earth's orbit around the Sun in

Our Image of the Week is a coloured engraving depicting the Earth’s orbit around the Sun in a solar year.

This Sunday marks the summer solstice in the northern hemisphere, the longest day of the year and the traditional beginning of the summer season.  For hundreds of years, this key astronomical event has been a time of celebration and was also used as a marking point, a date around which calendars were organized.

The summer solstice occurs when the earth is tilted on its axis at an angle that is most inclined towards the Sun. In the far north, this is a time of continuous daylight that ranges from a few days to six months depending on how close to the north pole you are.

Drawn and engraved by John Emslie in 1851, this image shows the summer and winter solstices as well as the spring and autumn equinoxes. Equinoxes are the days where the sun crosses the earth’s equator, making day and night time approximately equal in length.

Around the edges are the twelve signs of the zodiac, which represent twelve 30 degree sectors of the sun’s celestial path. Originating in Babylonian astrology, these signs are today mostly associated with horoscopes which represent the specific position of the sun at the time of a person’s birth. Western astronomy measures and divides the sky from the solstice and equinox points, meaning that the zodiac signs don’t in fact line up with their similarly-named constellations.

Image credit: Astronomy: a diagram of the Earth’s orbit around the Sun in a solar year. Coloured engraving by J. Emslie, 1851, Wellcome Library, London

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