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

Asteroid 23 Thalia at opposition

Dominic Ford, Editor
From the Asteroids feed

Objects: 23 Thalia
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The sky at

Asteroid 23 Thalia will be well placed, lying in the constellation Coma Berenices, well above the horizon for much of the night.

Regardless of your location on the Earth, 23 Thalia will reach its highest point in the sky around midnight local time.

From Fairfield, it will be visible in the morning sky, becoming accessible around 20:23, when it reaches an altitude of 22° above your eastern horizon. It will then reach its highest point in the sky at 01:31, 67° above your southern horizon. It will be lost to dawn twilight around 05:59, 29° above your 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 23 Thalia 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 23 Thalia lies opposite to the Sun in the night sky, the solar system is lined up so that 23 Thalia, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as 23 Thalia.

On this occasion, 23 Thalia will pass within 1.16 AU of us, reaching a peak brightness of magnitude 9.7. Nonetheless, even at its brightest, 23 Thalia is a faint object beyond the reach of the naked eye; binoculars or a telescope of moderate aperture are needed.

Finding 23 Thalia

The chart below indicates the path of 23 Thalia across the sky around the time of opposition.

It was produced using StarCharter and is available for download, either on dark background, in PNG, PDF or SVG formats, or on a light background, in PNG, PDF or SVG formats.

The position of 23 Thalia at the moment of opposition will be as follows:

Object Right Ascension Declination Constellation Magnitude
Asteroid 23 Thalia 12h06m30s 18°58'N Coma Berenices 9.7

The coordinates above are given in J2000.0.

The sky on 14 March 2024
Twilight ends
Twilight begins

4-day old moon
Waxing Crescent


4 days old

Rise Culm. Set
Mercury 07:37 13:52 20:07
Venus 06:23 11:45 17:07
Moon 09:16 16:55 00:43
Mars 05:59 11:09 16:18
Jupiter 09:10 16:08 23:05
Saturn 06:44 12:16 17:48
All times shown in EDT.


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 DE430 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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