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

Asteroid 23 Thalia at opposition

Dominic Ford, Editor
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The sky at

Asteroid 23 Thalia will be well placed for observation, lying in the constellation Taurus, 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 Cambridge, it will be visible between 18:07 and 04:59. It will become accessible around 18:07, when it rises to an altitude of 21° above your eastern horizon. It will reach its highest point in the sky at 23:31, 71° above your southern horizon. It will become inaccessible around 04:59 when it sinks below 21° 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 1.209 AU of us, reaching a peak brightness of magnitude 9.2. Nonetheless, even at its brightest, 23 Thalia 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 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 04h38m40s +23°31' Taurus 9.2

The coordinates above are given in J2000.0.

The sky on 03 December 2014
Sunrise
06:55
Sunset
16:11
Twilight ends
17:51
Twilight begins
05:14

11-day old moon
Waxing Gibbous

91%

11 days old

Planets
Rise Culm. Set
Mercury 06:45 11:21 15:57
Venus 07:45 12:15 16:45
Moon 14:41 21:33 03:19
Mars 10:21 14:59 19:37
Jupiter 21:32 04:35 11:34
Saturn 05:42 10:37 15:33
All times shown in EST.

Source

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.

Cambridge

Latitude:
Longitude:
Timezone:

42.38°N
71.11°W
EDT

Color scheme