© NASA/Galileo 1993. Pictured asteroid is 243 Ida.

Asteroid 433 Eros at opposition

Dominic Ford, Editor
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The sky at

Asteroid 433 Eros will be well placed for observation, lying in the constellation Camelopardalis, well above the horizon for much of the night.

Regardless of your location on the Earth, 433 Eros will reach its highest point in the sky at around midnight local time.

From Fairfield, it will be visible all night because it is circumpolar. It will be highest in the sky at 22:16, 71° above your northern horizon. At dusk, it will become visible at around 17:37 (EDT), 43° above your north-eastern horizon. It will be lost to dawn twilight at around 06:00, 24° above your north-western horizon.

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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 433 Eros 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 433 Eros lies opposite to the Sun in the night sky, the solar system is lined up so that 433 Eros, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as 433 Eros.

On this occasion, 433 Eros will pass within 0.241 AU of us, reaching a peak brightness of magnitude 9.4. Nonetheless, even at its brightest, 433 Eros 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 433 Eros

The star charts below mark the path of 433 Eros 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 433 Eros at the moment of opposition will be as follows:

Object Right Ascension Declination Constellation Magnitude
Asteroid 433 Eros 04h06m00s +60°03' Camelopardalis 9.4

The coordinates above are given in J2000.0.

The sky on 16 December 2018
Twilight ends
Twilight begins

9-day old moon
Waxing Gibbous


9 days old

Rise Culm. Set
Mercury 05:24 10:18 15:13
Venus 03:22 08:43 14:04
Moon 12:58 19:01 00:03
Mars 11:47 17:33 23:20
Jupiter 05:53 10:38 15:23
Saturn 08:14 12:52 17:30
All times shown in EST.


The circumstances of this event were computed from orbital elements made available by Ted Bowell of the Lowell Observatory. The conversion to geocentric coordinates was performed using the position of the Earth recorded in the DE405 ephemeris published by the Jet Propulsion Laboratory (JPL).

The star chart above shows the positions and magnitudes of stars as they appear in the Tycho catalogue. The data was reduced by the author and plotted using PyXPlot. A gnomonic projection of the sky has been used; celestial coordinates are indicated in the J2000.0 coordinate system.

Image credit

© NASA/Galileo 1993. Pictured asteroid is 243 Ida.




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