Neptune and 136199 Eris will share the same right ascension, with Neptune passing 6°42' to the north of 136199 Eris.
From Cambridge , the pair will be visible in the morning sky, becoming accessible around 22:47, when they reach an altitude of 21° above your eastern horizon. They will then reach their highest point in the sky at 02:58, 50° above your southern horizon. They will be lost to dawn twilight around 05:14, 40° above your south-western horizon.
Neptune will be at mag 7.8, and 136199 Eris at mag 18.6, both in the constellation Pisces.
A graph of the angular separation between Neptune and 136199 Eris around the time of closest approach is available here.
The positions of the two objects at the moment of conjunction will be as follows:
| Object | Right Ascension | Declination | Constellation | Magnitude | Angular Size |
| Neptune | 01h55m30s | 9°56'N | Pisces | 7.8 | 2"3 |
| 136199 Eris | 01h55m30s | 3°13'N | Pisces | 18.6 | 0"0 |
The coordinates above are given in J2000.0. The pair will be at an angular separation of 142° from the Sun, which is in Leo at this time of year.
The sky on 4 May 2025
| The sky on 4 May 2025 | ||||||||||||||||||||||||||||||||||
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53% 7 days old |
All times shown in EDT.
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Source
The circumstances of this event were computed using the DE430 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
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Image credit
The Moon in conjunction with Venus and Jupiter, with the Very Large Telescope in the foreground. Image © Y. Beletsky, ESO, 2009.