1 Ceres will reach opposition, when it lies opposite to the Sun in the sky. Lying in the constellation Taurus, it will be visible for much of the night, reaching its highest point in the sky around midnight local time.
From Cambridge, it will be visible between 18:29 and 04:31. It will become accessible at around 18:29, when it rises to an altitude of 21° above your eastern horizon. It will reach its highest point in the sky at 23:30, 64° above your southern horizon. It will become inaccessible at around 04:31 when it sinks below 21° above your western horizon.
A close approach to the Earth
At around the same time that 1 Ceres passes opposition, it also makes its closest approach to the Earth – termed its perigee – making it appear at its brightest.
This happens because when 1 Ceres lies opposite to the Sun in the sky, the Earth passes between 1 Ceres and the Sun. The solar system is lined up with 1 Ceres and the Earth on the same side of the Sun, as shown by the configuration labelled perigee in the diagram below:
When a planet is at opposition, the solar system is aligned such that the planet
lies on the same side of the Sun as the Earth. At this time, the planet makes its
perigee, or closest approach to the Earth.
Not drawn to scale.
In practice, however, 1 Ceres orbits much further out in the solar system than the Earth – at an average distance from the Sun of 2.77 times that of the Earth, and so its brightness does not vary much as it cycles between opposition and solar conjunction.
Observing 1 Ceres
At opposition, 1 Ceres is visible for much of the night. When it lies opposite to the Sun in the sky, this means that it rises at around the time the Sun sets, and it sets at around the time the Sun rises. It reaches its highest point in the sky at around midnight local time.
But even when it is at its closest point to the Earth, 1 Ceres is so distant from the Earth that it is not possible to distinguish it as more than a star-like point of light, even through a telescope.
A chart of the path of 1 Ceres across the sky in 2021 can be found here, and a chart of its rising and setting times here.
At the moment of opposition, 1 Ceres will lie at a distance of 1.76 AU, and reach a peak brightness of magnitude 7.0. Its celestial coordinates at the moment it passes opposition will be:
| Object | Right Ascension | Declination | Constellation | Magnitude | Angular Size |
| 1 Ceres | 04h15m00s | 16°43'N | Taurus | 7.0 | 0.0" |
The coordinates above are given in J2000.0.
Over the weeks following its opposition, 1 Ceres will reach its highest point in the sky four minutes earlier each night, gradually receding from the pre-dawn morning sky while remaining visible in the evening sky for a few months.
The sky on 27 Nov 2021
| The sky on 27 November 2021 | ||||||||||||||||||||||||||||||||||
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47% 23 days old |
All times shown in EST.
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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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| 27 Nov 2021 | – 1 Ceres at opposition |
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| 02 Oct 2025 | – 1 Ceres at opposition |
Image credit
© NASA/Dawn 2015