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

Asteroid 27 Euterpe at opposition

Dominic Ford, Editor
From the Asteroids feed

Objects: 27 Euterpe
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The sky at

Asteroid 27 Euterpe will be well placed, lying in the constellation Cetus, well above the horizon for much of the night.

Regardless of your location on the Earth, 27 Euterpe will reach its highest point in the sky around midnight local time.

From Fairfield, it will be visible between 20:43 and 04:55. It will become accessible around 20:43, when it rises to an altitude of 21° above your eastern horizon. It will reach its highest point in the sky at 00:49, 50° above your southern horizon. It will become inaccessible around 04:55 when it sinks below 22° 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 27 Euterpe 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 27 Euterpe lies opposite to the Sun in the night sky, the solar system is lined up so that 27 Euterpe, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as 27 Euterpe.

On this occasion, 27 Euterpe will pass within 1.221 AU of us, reaching a peak brightness of magnitude 9.4. Nonetheless, even at its brightest, 27 Euterpe is a faint object beyond the reach of the naked eye; binoculars or a telescope of moderate aperture are needed.

Finding 27 Euterpe

The chart below indicates the path of 27 Euterpe 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 27 Euterpe at the moment of opposition will be as follows:

Object Right Ascension Declination Constellation Magnitude
Asteroid 27 Euterpe 00h41m40s 1°23'N Cetus 9.4

The coordinates above are given in J2000.0.

The sky on 27 November 2021
Twilight ends
Twilight begins

23-day old moon
Waning Crescent


23 days old

Rise Culm. Set
Mercury 06:55 11:37 16:20
Venus 10:21 14:46 19:12
Moon 22:50 06:01 13:03
Mars 05:32 10:33 15:33
Jupiter 12:04 17:16 22:28
Saturn 11:17 16:10 21:04
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 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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