Tuesday 11 January 2022

Asteroid 7 Iris comes to opostition.

Asteroid 7 Iris will reach opposition (the point at which it is directly opposite the Sun when observed from the Earth) at 9.344 pm GMT on Thursday 11 January 2022, when it will also be at the closest point on its orbit to the Earth, 1.01 AU (i.e. 1.01 times as far from the Earth as the Sun, or about 164 408 000 km), and be completely illuminated by the Sun. While it is not obvious to the naked eye observer, asteroids have phases just like those of the Moon; being further from the Sun than the Earth, 7 Iris is 'full' when directly opposite the Sun. As 7 Iris is only about 240 km in diameter, it will not be visible to the naked eye, but with a maximum Apparent Magnitude (luminosity) of 7.7 at opposition, it should be visible in the Constellation of Corvus to viewers equipped with a good pair of binoculars or small telescope.
Asteroid 7 Iris was discovered on 13 August 1873 by English Astronomer John Russel Hind, then at George Bishop's Observatory in London. It was the seventh asteroid discovered, and was named after the Greek goddess Iris, the personification of the rainbow, and a messenger of the gods.

The calculated orbit and current position 7 Iris.  JPL Small Body Database

7 Iris has a 1346 day orbital period and an eccentric orbit tilted at an angle of 5.52° to the plane of the Solar System, which takes it from 1.83 AU from the Sun (i.e. 183% of the average distance at which the Earth orbits the Sun) to 2.94 AU from the Sun (i.e. 294% of the average distance at which the Earth orbits the Sun). As an asteroid that never comes within 1.666 AU of the Sun and has an average orbital distance less than 3.2 AU from the Sun, 7 Iris is classed as a Main Belt Asteroid. 

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