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

Asteroid 10 Hygiea at opposition

Dominic Ford, Editor
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The sky at

Asteroid 10 Hygiea will be well placed for observation, lying in the constellation Sagittarius, well above the horizon for much of the night.

Regardless of your location on the Earth, 10 Hygiea will reach its highest point in the sky around midnight local time.

From Fairfield, it will be visible between 23:26 and 02:26. It will become accessible around 23:26, when it rises to an altitude of 21° above your southern horizon. It will reach its highest point in the sky at 00:58, 25° above your southern horizon. It will become inaccessible around 02:26 when it sinks below 22° above your southern 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 10 Hygiea 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 10 Hygiea lies opposite to the Sun in the night sky, the solar system is lined up so that 10 Hygiea, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as 10 Hygiea.

On this occasion, 10 Hygiea will pass within 1.852 AU of us, reaching a peak brightness of magnitude 9.1. Nonetheless, even at its brightest, 10 Hygiea 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 10 Hygiea

The chart below indicates the path of 10 Hygiea 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 10 Hygiea at the moment of opposition will be as follows:

Object Right Ascension Declination Constellation Magnitude
Asteroid 10 Hygiea 18h35m40s -23°42' Sagittarius 9.1

The coordinates above are given in J2000.0.

The sky on 29 June 2017
Sunrise
05:22
Sunset
20:28
Twilight ends
22:36
Twilight begins
03:14

5-day old moon
Waxing Crescent

39%

5 days old

Planets
Rise Culm. Set
Mercury 06:02 13:38 21:13
Venus 02:48 09:50 16:52
Moon 11:46 18:05 00:24
Mars 05:59 13:32 21:04
Jupiter 13:23 19:12 01:04
Saturn 19:08 23:50 04:35
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 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