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

Asteroid 42 Isis at opposition

Dominic Ford, Editor
From the Asteroids feed

Objects: 42 Isis
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The sky at

Asteroid 42 Isis will be well placed, lying in the constellation Piscis Austrinus, well above the horizon for much of the night.

Regardless of your location on the Earth, 42 Isis will reach its highest point in the sky around midnight local time.

From Cambridge however, it will not be readily observable since it will lie so far south that it will never rise more than 19° above the 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 42 Isis 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 42 Isis lies opposite to the Sun in the night sky, the solar system is lined up so that 42 Isis, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as 42 Isis.

On this occasion, 42 Isis will pass within 0.905 AU of us, reaching a peak brightness of magnitude 9.5. Nonetheless, even at its brightest, 42 Isis is a faint object beyond the reach of the naked eye; binoculars or a telescope of moderate aperture are needed.

Finding 42 Isis

The chart below indicates the path of 42 Isis 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 42 Isis at the moment of opposition will be as follows:

Object Right Ascension Declination Constellation Magnitude
Asteroid 42 Isis 22h03m30s 28°19'S Piscis Austrinus 9.5

The coordinates above are given in J2000.0.

The sky on 14 Aug 2028

The sky on 14 August 2028
Sunrise
05:47
Sunset
19:46
Twilight ends
21:33
Twilight begins
03:59

23-day old moon
Waning Crescent

32%

23 days old

Planets
Rise Culm. Set
Mercury 07:25 13:59 20:33
Venus 02:15 09:37 16:59
Moon 23:24 07:11 15:05
Mars 02:44 10:20 17:56
Jupiter 08:52 15:02 21:13
Saturn 22:57 05:47 12:38
All times shown in EDT.

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 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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Cambridge

Latitude:
Longitude:
Timezone:

42.38°N
71.11°W
EST

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