© NASA/Dawn 2015

1 Ceres at opposition

Dominic Ford, Editor
From the Dwarf Planets feed

Objects: 1 Ceres
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The sky at

1 Ceres will reach opposition, when it lies opposite to the Sun in the sky. Lying in the constellation Cetus, it will be visible for much of the night, reaching its highest point in the sky around midnight local time.

From Fairfield, it will be visible between 21:52 and 04:24. It will become accessible around 21:52, when it rises to an altitude of 22° above your south-eastern horizon. It will reach its highest point in the sky at 01:08, 39° above your southern horizon. It will become inaccessible around 04:24 when it sinks below 21° above your south-western horizon.

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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 2025 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 1.96 AU, and reach a peak brightness of magnitude 7.8. Its celestial coordinates at the moment it passes opposition will be:

Object Right Ascension Declination Constellation Magnitude Angular Size
1 Ceres 01h01m00s 9°48'S Cetus 7.8 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 03 October 2025
Sunrise
06:50
Sunset
18:34
Twilight ends
20:06
Twilight begins
05:18

12-day old moon
Waxing Gibbous

86%

12 days old

Planets
Rise Culm. Set
Mercury 08:10 13:38 19:05
Venus 04:53 11:18 17:44
Moon 16:52 22:12 03:42
Mars 09:12 14:25 19:38
Jupiter 00:19 07:43 15:08
Saturn 18:06 23:57 05:48
All times shown in EDT.

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.

Related news

03 Oct 2025  –  1 Ceres at opposition
08 Jan 2027  –  1 Ceres at opposition
18 Jul 2027  –  1 Ceres at perihelion
07 May 2028  –  1 Ceres at opposition

Image credit

© NASA/Dawn 2015

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