Thursday 12 October 2017

Uranus reaches opposition.

The planet Neptune will reach opposition (i.e. be directly opposite the Sun seen from Earth) at  5.21 pm GMT on Thursday 19 October 2017. This means that it will both be at its closest to the Earth this year, about 18.91 AU (18.91 times the average distance between the Earth and the Sun, or about 2 829 000 000 km), and completely illuminated by the Sun. While it is not visible to the naked eye observer, the planets have phases just like those of the Moon; being further from the Sun than the Earth, Neptune is 'full' when directly opposite the Sun. 

The planet Uranus.

While the relative positions of the planets have no direct influence on life on Earth, the opposition of Saturn does present the best opportunity for observations of the planet by Earth-based observers. Uranus is never visible to the naked eye, but on Thursday 19 October the planet will be visible with a reasonable telescope in the constellation of  Pisces, rising at about 8.14 pm in the southeast in the Northern Hemisphere and the northeast in the Southern Hemisphere reaching its highest in the sky at about 0.48 am, and setting in the west at about 5.18 am.

Uranus orbits the Sun at an average distance of 19.2 AU, completing one orbit around the Sun every 84 years. This means that the planet is almost stationary compared to the faster moving Earth, so that it reaches Solar Opposition only four days later each year than the year before, and reaches conjunction (when it is directly behind the Sun seen from the Earth), roughly six months later.

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