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

Asteroid 5 Astraea at opposition

Dominic Ford, Editor
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The sky at

Asteroid 5 Astraea will be well placed for observation, lying in the constellation Cancer, well above the horizon for much of the night.

Regardless of your location on the Earth, 5 Astraea will reach its highest point in the sky around midnight local time.

From Fairfield, it will be visible between 18:58 and 05:01. It will become accessible around 18:58, when it rises to an altitude of 21° above your eastern horizon. It will reach its highest point in the sky at 23:57, 65° above your southern horizon. It will become inaccessible around 05:01 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 5 Astraea 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 5 Astraea lies opposite to the Sun in the night sky, the solar system is lined up so that 5 Astraea, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as 5 Astraea.

On this occasion, 5 Astraea will pass within 1.111 AU of us, reaching a peak brightness of magnitude 8.9. Nonetheless, even at its brightest, 5 Astraea 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 5 Astraea

The chart below indicates the path of 5 Astraea 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 5 Astraea at the moment of opposition will be as follows:

Object Right Ascension Declination Constellation Magnitude
Asteroid 5 Astraea 08h08m50s +16°24' Cancer 8.9

The coordinates above are given in J2000.0.

The sky on 21 January 2020
Sunrise
07:12
Sunset
16:53
Twilight ends
18:30
Twilight begins
05:35

26-day old moon
Waning Crescent

9%

26 days old

Planets
Rise Culm. Set
Mercury 07:47 12:35 17:23
Venus 09:06 14:36 20:06
Moon 04:32 09:15 13:58
Mars 03:53 08:33 13:14
Jupiter 06:02 10:39 15:16
Saturn 06:49 11:32 16:16
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.

Fairfield

Latitude:
Longitude:
Timezone:

41.14°N
73.26°W
EDT

Color scheme