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

Asteroid 29 Amphitrite at opposition

Fri, 03 Mar 2017 at11:46 EST(320 days ago)
16:46 UTC

Dominic Ford, Editor
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The sky at

Asteroid 29 Amphitrite will be well placed for observation, lying in the constellation Leo, well above the horizon for much of the night.

Regardless of your location on the Earth, 29 Amphitrite will reach its highest point in the sky at around midnight local time.

From Ashburn (click to change), it will be visible between 20:02 and 04:45. It will become accessible at around 20:02, when it rises 24° above your eastern horizon, and then reach its highest point in the sky at 00:26, 59° above your southern horizon. It will become inaccessible at around 04:45 when it sinks to 25° above your western 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 29 Amphitrite 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 29 Amphitrite lies opposite to the Sun in the night sky, the solar system is lined up so that 29 Amphitrite, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as 29 Amphitrite.

On this occasion, 29 Amphitrite will pass within 1.598 AU of us, reaching a peak brightness of magnitude 9.1. Nonetheless, even at its brightest, 29 Amphitrite 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 29 Amphitrite

The star charts below mark the path of 29 Amphitrite 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 29 Amphitrite at the moment of opposition will be as follows:

Object Right Ascension Declination Constellation Magnitude
Asteroid 29 Amphitrite 11h00m50s +08°49' Leo 9.1

The coordinates above are given in J2000.0.

The sky on 03 March 2017
Sunrise 06:38
Sunset 18:03
Twilight ends
Twilight begins

5-day old moon
Age of Moon
5 days

All times shown in EST.
Rise Culm. Set
Mercury 06:41 12:12 17:44
Venus 07:18 13:59 20:40
Moon 10:00 16:47 23:34
Mars 08:21 14:56 21:31
Jupiter 21:04 02:48 08:27
Saturn 02:23 07:09 11:56


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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