The dwarf planet 136199 Eris will reach opposition (i.e. be directly opposite the
Sun seen from Earth) on Thursday 17 October 2019 at 5.10 pm GMT. This
means that it will both be at its closest to the Earth this year, about 95.05 AU (95.05 times the average distance between the Earth and the
Sun, or about 2 945 150 000 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, 136199 Eris is 'full' when directly opposite the Sun. As this falls
only four days after the Full Moon, the prospects for viewing for those
equipped with suitable telescopes is not as good as it might be. The
planet will be in the constellation of Cetus and at its highest point
in the sky at about 1.05 am local time from anywhere on Earth (this is because the rising and setting of objects in the sky is caused by the Earth's rotation, not the movement of the object). (Even at it's very brightest 136199 Eris will only have a Magnitude of 18.7, making it almost impossible to see with any but the largest of Earth-based telescopes, and where resolvable it will only be possible to see it as a point of light indistinguishable from a faint star.
The orbit and current position of 136199 Eris. JPL Small Body Database Browser.
136199 Eris orbits the Sun on an eccentric orbit
tilted at an angle of 44.1° to the plane of the Solar System, which
takes it from 35.9 AU from the Sun (35.9 times the average distance at
which the Earth orbits the Sun) to 97.5 AU from the Sun (97.5 times
the
average distance at which the Earth orbits the Sun. With an average distance of 67.74 AU, 136199 Eris completes
one
orbit around the Sun every 558 years. This means that the planet is
almost stationary compared to the faster moving Earth, so that it
reaches Opposition only four days later each year than the year
before, and reaches Solar Conjunction (when it is directly on the
opposite side of the Sun to the Earth), roughly six months later.
136199 Eris was discovered on 5 January 2005 by a team led by Mike Brown of the Palomar Observatory in California. With a diameter of 2326 km it is considered to be the second largest dwarf planet in the Solar System (after 134340 Pluto) as well as the sixteenth most largest body in the Solar System, excluding the Sun (though several moons, including our own, are larger). It is also the largest body in the Solar System never to have been visited by a spacecraft (again, with the exception of the Sun), and (currently) the second most distant known object in the Solar System, after trans-Neptunian Object 2018 VG18. 136199 Eris has a single moon, Dysnomia, which has a diameter of about 700 km and obits at a distance of about 37 350 km.
136199 Eris was discovered on 5 January 2005 by a team led by Mike Brown of the Palomar Observatory in California. With a diameter of 2326 km it is considered to be the second largest dwarf planet in the Solar System (after 134340 Pluto) as well as the sixteenth most largest body in the Solar System, excluding the Sun (though several moons, including our own, are larger). It is also the largest body in the Solar System never to have been visited by a spacecraft (again, with the exception of the Sun), and (currently) the second most distant known object in the Solar System, after trans-Neptunian Object 2018 VG18. 136199 Eris has a single moon, Dysnomia, which has a diameter of about 700 km and obits at a distance of about 37 350 km.
