British Astronomical Association
Supporting amateur astronomers since 1890

Secondary menu

Main menu

BAA Observing calendar

Dwarf Planet 1 Ceres at opposition

Wednesday, 2019, May 29 - 05:48

Dwarf Planet 1 Ceres will be well placed for observation, lying in the constellation Ophiuchus, well above the horizon for much of the night.

Regardless of your location on the Earth, 1 Ceres will reach its highest point in the sky at around midnight local time.

From London however, it will not be readily observable since it will lie so far south that it will never rise more than 20° above the horizon.

The geometry of the alignment

This optimal positioning occurs when it makes its closest approach to the point in the sky directly opposite to the Sun – an event termed opposition. Since the Sun reaches its greatest distance below the horizon at midnight, the point opposite to it is highest in the sky at the same time.

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 in the night sky. This happens because when 1 Ceres lies opposite to the Sun in the night sky, the solar system is lined up so that 1 Ceres, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as 1 Ceres.

On this occasion, 1 Ceres will pass within 1.758 AU of us, reaching a peak brightness of magnitude 7.0. Nonetheless, even at its brightest, 1 Ceres is a faint object beyond the reach of the naked eye or binoculars; a telescope of moderate aperture and a good star chart are needed.

Finding 1 Ceres

The star charts below mark the path of 1 Ceres across the sky around the time of its opposition.

This star chart is also available to download:

Light-on-dark PNG image PDF document
Dark-on-light PNG image PDF document

The exact position of 1 Ceres at the moment of opposition will be as follows:

Object Right Ascension Declination Constellation Magnitude
Dwarf Planet 1 Ceres 16h23m50s -17°42' Ophiuchus 7.0

The coordinates above are given in J2000.0.

This entry in the observing calendar was provided by In-The-Sky.org

.