Courtesy of EarthSky
A Clear Voice for Science
Pluto – the former planet – comes to opposition on June 25, at 19:00 Universal Time. That is when we on Earth pass more or less between the sun and Pluto, so that this distant world is now opposite the sun in our sky.
Of course, in Pluto’s case, it is not exactly opposite since the orbit of Pluto is inclined to the plane of the solar system by 17 degrees. That is a greater inclination than the orbits of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus or Neptune … and it is one thing that has always set Pluto apart. Pluto’s differences ultimately lost this world its planet status, according to a 2006 decision by astronomers of the International Astronomical Union.
Pluto is closest to us now for the year at just over four light-hours away. And,because it is most nearly opposite the sun, Pluto does rise within about half an hour of sunset on June 22. This mysterious world is now highest in the south when the sun is below our feet at midnight. It is not possible to see Pluto with the eye. Pluto is some thousand times too faint to be viewed with the eye alone. However, look for the Teapot star pattern in the constellation Sagittarius, and you can imagine Pluto’s location with your mind’s eye.
Each opposition of Pluto brings it closest and brightest for the year. Yet, Pluto is not as close to us at this year’s opposition as it was last year. Pluto was closest to the sun in its 248-year orbit in 1989. Throughout the 1980s and 1990s, it was closer to the sun than was Neptune. Thus, Pluto was closer to us – and brighter than it is tonight – at its oppositions during those years. It is now farther away from the sun – and thus from us – at each successive opposition.
Related: Pluto saga continues a word on the ongoing debate about Pluto
Coming soon . . .