Pluto
Pluto is currently visible as a morning object. From Cambridge, however, it is not observable – it will reach its highest point in the sky during daytime and is no higher than 20° above the horizon at dawn.
Pluto, as seen by New Horizons. Image courtesy of NASA.
Pluto is a dwarf planet which orbits in an outer region of the solar system known as the Edgeworth-Kuiper belt. Its formal minor-planet designation is 134340 Pluto.
From its discovery in 1930 until 2006, Pluto was considered to be the solar system's outermost known planet. However, it is much smaller than the other planets, measuring 18% of the diameter of the Earth, and less than half the diameter of the next smallest planet, Mercury.
In the early 2000s, its status as a planet became increasingly untenable due to theoretical predictions of large numbers of other similarly-sized objects in the Edgeworth-Kuiper belt.
Pluto was at last downgraded from its status as a planet in 2006, and given the newly-generated title of dwarf planet. This was prompted by the discovery of another Edgeworth-Kuiper belt object, which was 27% more massive than Pluto. In view of its role in history, that object was named Eris, after the goddess of strife of discord in Greek mythology; Eris was also classified as a dwarf planet.
Apparitions of Pluto
The table below lists apparitions of Pluto around the year 2024, computed from NASA's DE430 planetary ephemeris. To show events around other years, use the control below.
Apparitions of Pluto around 2024
| Date | Event | Declination |
| Date | Event | Declination |
| 04 Jul 2014 09:53 EDT | 134340 Pluto at opposition | 20°16'S |
| 06 Jul 2015 17:44 EDT | 134340 Pluto at opposition | 20°41'S |
| 08 Jul 2016 00:49 EDT | 134340 Pluto at opposition | 21°05'S |
| 10 Jul 2017 07:14 EDT | 134340 Pluto at opposition | 21°26'S |
| 12 Jul 2018 13:00 EDT | 134340 Pluto at opposition | 21°46'S |
| 14 Jul 2019 18:05 EDT | 134340 Pluto at opposition | 22°04'S |
| 15 Jul 2020 22:45 EDT | 134340 Pluto at opposition | 22°19'S |
| 18 Jul 2021 02:38 EDT | 134340 Pluto at opposition | 22°34'S |
| 20 Jul 2022 05:49 EDT | 134340 Pluto at opposition | 22°46'S |
| 22 Jul 2023 08:23 EDT | 134340 Pluto at opposition | 22°57'S |
| 23 Jul 2024 10:29 EDT | 134340 Pluto at opposition | 23°06'S |
| 25 Jul 2025 11:44 EDT | 134340 Pluto at opposition | 23°13'S |
| 27 Jul 2026 12:28 EDT | 134340 Pluto at opposition | 23°19'S |
| 29 Jul 2027 12:42 EDT | 134340 Pluto at opposition | 23°24'S |
| 30 Jul 2028 12:20 EDT | 134340 Pluto at opposition | 23°27'S |
| 01 Aug 2029 11:34 EDT | 134340 Pluto at opposition | 23°28'S |
| 03 Aug 2030 09:59 EDT | 134340 Pluto at opposition | 23°29'S |
| 05 Aug 2031 08:14 EDT | 134340 Pluto at opposition | 23°28'S |
| 06 Aug 2032 05:58 EDT | 134340 Pluto at opposition | 23°26'S |
| 08 Aug 2033 03:04 EDT | 134340 Pluto at opposition | 23°22'S |
Finding Pluto
Pluto comes to opposition once every 367 days – its synodic period – almost exactly once a year. The date it comes to opposition moves only one day later each year.
Pluto is a faint and distant object. At around magnitude 14, it is beyond the reach of all but the largest amateur telescopes. Pluto's largest moon, Charon, is not much smaller than Pluto itself, measuring a little under 10% of the diameter of the Earth, and appears 2–3 magnitudes fainter. Two other much smaller moons, Nix and Hydra, were discovered in 2005.
A chart of the time of day when Pluto rises and sets on any given day of the year can be found here. A chart of Pluto's path relative to the background stars can be found here.
Pluto has only ever been visited once by one spacecraft: the NASA New Horizons probe flew past it in 2015 before going on to study other Edgeworth-Kuiper belt objects.
| NORAD ID | COSPAR ID | Name | Launch date | Flight ended | Owner |
| NORAD ID | COSPAR ID | Name | Launch date | Flight ended | Owner |
| 28928 | 2006-001A | NEW HORIZONS | 19 Jan 2006 | United States |